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"An idea is fragile . It can be killed by a scornful smile or a yawn .It can be mound down by irony and scared to death by a cold look."
"Most cultures throughout human history have not liked creative individuals .They ignore them or kill them.It is a very efficient way of stopping creativity."

------Advertising boss Charles Browe and Howard Gardner ,professor at Harvard

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2010年12月7日 #

make judge on a natural number: if it's equals to pow(x, 2) and x is a natural number too.

bool isPowered2(int n, int low, int hig, int dvd)
int mid = (low+hig)/dvd;
int pwr = mid*mid;
if(pwr == n) return true;
else if(low == hig) return false;

if(pwr > n) { // target number is in [low, mid-1]
        return isPowered2(n, low, mid-1, dvd);

if(pwr < n) { // target number is in [mid+1, hig]
        return isPowered2(n, mid+1, hig, 2); // use binary searching here.

bool isPowered(int n)
if(n <= 100) {
if(n <= 25)
if(n == 1 || n == 4 || n == 9 || n == 16 || n == 25return true;
if(n == 36 || n == 49 || n == 64 || n == 81 || n == 100return true;
else return false;

return isPowered2(n, 1, n-1, 10); // why use 10 here ?

posted @ 2010-12-07 10:50 JonsenElizee 阅读(318) | 评论 (1)编辑 收藏

2010年12月2日 #

#include <sys/types.h>

pid_t waitpid(pid_t pid, 
int* status, int options);

< -1 wait for any process with group id value = -pid;
= -1 same as wait();
= 0 wait for any subprocess of this process;
> 0 wait for process with it's id = pid;

= 0 don't use options;
    WNOHANG  : just return if no subprocess finished.
    WUNTRACED: just 
return if subprocess is hanged up now.

status the 
return status of subprocess is stored in this int value.
    to make sure what happed, we can use following macro:
    WIFEXITED(status)      如果子进程正常结束则为非0值。
    WEXITSTATUS(status)    取得子进程exit()返回的结束代码,一般会先用WIFEXITED来判断是否正常结束才能使用此宏。
    WIFSIGNALED(status)    如果子进程是因为信号而结束则此宏值为真
    WTERMSIG(status)       取得子进程因信号而中止的信号代码,一般会先用WIFSIGNALED来判断后才使用此宏。
    WIFSTOPPED(status)     如果子进程处于暂停执行情况则此宏值为真。一般只有使用WUNTRACED时才会有此情况。
    WSTOPSIG(status)       取得引发子进程暂停的信号代码,一般会先用WIFSTOPPED来判断后才使用此宏。

return pid the subprocess id, else -1 for error, and errno is set.

posted @ 2010-12-02 15:28 JonsenElizee 阅读(274) | 评论 (0)编辑 收藏

2010年12月1日 #

B+ tree

From Wikipedia, the free encyclopedia
Jump to: navigation, search
A simple B+ tree example linking the keys 1–7 to data values d1-d7. The linked list (red) allows rapid in-order traversal.

In computer science, a B+ tree or B plus tree is a type of tree which represents sorted data in a way that allows for efficient insertion, retrieval and removal of records, each of which is identified by a key. It is a dynamic, multilevel index, with maximum and minimum bounds on the number of keys in each index segment (usually called a "block" or "node"). In a B+ tree, in contrast to a B-tree, all records are stored at the leaf level of the tree; only keys are stored in interior nodes.

The primary value of a B+ tree is in storing data for efficient retrieval in a block-oriented storage context—in particular, filesystems. This is primarily because unlike binary search trees, B+ trees have very high fanout (typically on the order of 100 or more), which reduces the number of I/O operations required to find an element in the tree.

NTFS, ReiserFS, NSS, XFS, and JFS filesystems all use this type of tree for metadata indexing. Relational database management systems such as IBM DB2[1], Informix[1], Microsoft SQL Server[1], Oracle 8[1], Sybase ASE[1], PostgreSQL[2], Firebird, MySQL[3] and SQLite[4] support this type of tree for table indices. Key-value database management systems such as CouchDB[5], Tokyo Cabinet[6] and Tokyo Tyrant support this type of tree for data access. InfinityDB[7] is a concurrent BTree.



[edit] Details

The order, or branching factor b of a B+ tree measures the capacity of nodes (i.e. the number of children nodes) for internal nodes in the tree. The actual number of children for a node, referred to here as m, is constrained for internal nodes so that  \lceil b/2 \rceil \le m \le b. The root is an exception: it is allowed to have as few as two children. For example, if the order of a B+ tree is 7, each internal node (except for the root) may have between 4 and 7 children; the root may have between 2 and 7. Leaf nodes have no children , but are constrained so that the number of keys must be at least  \lceil (b-1)/2 \rceil and at most b − 1. In the situation where a B+ tree is nearly empty, it only contains one node, which is a leaf node. (The root is also the single leaf, in this case.) This node is permitted to have as little as one key if necessary.

[edit] Search

The algorithm to perform a search for a record r follows pointers to the correct child of each node until a leaf is reached. Then, the leaf is scanned until the correct record is found (or until failure).

  function search(record r)
u := root
while (u is not a leaf) do
choose the correct pointer in the node
move to the first node following the pointer
u := current node
scan u for r

This pseudocode assumes that no repetition is allowed.

[edit] Insertion

Perform a search to determine what bucket the new record should go in.

  • if the bucket is not full, add the record.
  • otherwise, split the bucket.
    • allocate new leaf and move half the bucket's elements to the new bucket
    • insert the new leaf's smallest key and address into the parent.
    • if the parent is full, split it also
      • add the middle key to the parent node
    • repeat until a parent is found that need not split
  • if the root splits, create a new root which has one key and two pointers.

[edit] Characteristics

For a b-order B+ tree with h levels of index:

  • The maximum number of records stored is nmax = bhbh − 1
  • The minimum number of keys is n_{kmin} = 2\left(\frac{b}{2}\right)^{h-1}
  • The space required to store the tree is O(n)
  • Inserting a record requires O(logbn) operations in the worst case
  • Finding a record requires O(logbn) operations in the worst case
  • Removing a (previously located) record requires O(logbn) operations in the worst case
  • Performing a range query with k elements occurring within the range requires O(logbn + k) operations in the worst case.

[edit] Implementation

The leaves (the bottom-most index blocks) of the B+ tree are often linked to one another in a linked list; this makes range queries or an (ordered) iteration through the blocks simpler and more efficient (though the aforementioned upper bound can be achieved even without this addition). This does not substantially increase space consumption or maintenance on the tree. This illustrates one of the significant advantages of a B+-tree over a B-tree; in a B-tree, since not all keys are present in the leaves, such an ordered linked list cannot be constructed. A B+-tree is thus particularly useful as a database system index, where the data typically resides on disk, as it allows the B+-tree to actually provide an efficient structure for housing the data itself (this is described in [8] as index structure "Alternative 1").

If a storage system has a block size of B bytes, and the keys to be stored have a size of k, arguably the most efficient B+ tree is one where b = (B / k) − 1. Although theoretically the one-off is unnecessary, in practice there is often a little extra space taken up by the index blocks (for example, the linked list references in the leaf blocks). Having an index block which is slightly larger than the storage system's actual block represents a significant performance decrease; therefore erring on the side of caution is preferable.

If nodes of the B+ tree are organized as arrays of elements, then it may take a considerable time to insert or delete an element as half of the array will need to be shifted on average. To overcome this problem, elements inside a node can be organized in a binary tree or a B+ tree instead of an array.

B+ trees can also be used for data stored in RAM. In this case a reasonable choice for block size would be the size of processor's cache line. However, some studies have proved that a block size a few times larger than the processor's cache line can deliver better performance if cache prefetching is used.

Space efficiency of B+ trees can be improved by using some compression techniques. One possibility is to use delta encoding to compress keys stored into each block. For internal blocks, space saving can be achieved by either compressing keys or pointers. For string keys, space can be saved by using the following technique: Normally the ith entry of an internal block contains the first key of block i+1. Instead of storing the full key, we could store the shortest prefix of the first key of block i+1 that is strictly greater (in lexicographic order) than last key of block i. There is also a simple way to compress pointers: if we suppose that some consecutive blocks i, i+1...i+k are stored contiguously, then it will suffice to store only a pointer to the first block and the count of consecutive blocks.

All the above compression techniques have some drawbacks. First, a full block must be decompressed to extract a single element. One technique to overcome this problem is to divide each block into sub-blocks and compress them separately. In this case searching or inserting an element will only need to decompress or compress a sub-block instead of a full block. Another drawback of compression techniques is that the number of stored elements may vary considerably from a block to another depending on how well the elements are compressed inside each block.

[edit] History

The B tree was first described in the paper Organization and Maintenance of Large Ordered Indices. Acta Informatica 1: 173–189 (1972) by Rudolf Bayer and Edward M. McCreight. There is no single paper introducing the B+ tree concept. Instead, the notion of maintaining all data in leaf nodes is repeatedly brought up as an interesting variant. An early survey of B trees also covering B+ trees is Douglas Comer: "The Ubiquitous B-Tree", ACM Computing Surveys 11(2): 121–137 (1979). Comer notes that the B+ tree was used in IBM's VSAM data access software and he refers to an IBM published article from 1973.

[edit] See also

[edit] References

  1. ^ a b c d e Ramakrishnan Raghu, Gehrke Johannes - Database Management Systems, McGraw-Hill Higher Education (2000), 2nd edition (en) page 267
  2. ^ PostgreSQL documentation
  3. ^ Colin Charles Agenda - Morning sessions at MySQL MiniConf
  4. ^ SQLite Version 3 Overview
  5. ^ CouchDB Guide (see note after 3rd paragraph)
  6. ^ Tokyo Cabinet reference
  7. ^ The Design Of The InfinityDB Database Engine
  8. ^ Ramakrishnan, R. and Gehrke, J. Database Management Systems, McGraw-Hill Higher Education (2002), 3rd edition

[edit] External links

posted @ 2010-12-01 11:48 JonsenElizee 阅读(1728) | 评论 (0)编辑 收藏


From Wikipedia, the free encyclopedia
Jump to: navigation, search
Simple example of an R-tree for 2D rectangles
Visualization of an R*-tree for 3D cubes using ELKI

R-trees are tree data structures that are similar to B-trees, but are used for spatial access methods, i.e., for indexing multi-dimensional information; for example, the (X, Y) coordinates of geographical data. A common real-world usage for an R-tree might be: "Find all museums within 2 kilometres (1.2 mi) of my current location".

The data structure splits space with hierarchically nested, and possibly overlapping, minimum bounding rectangles (MBRs, otherwise known as bounding boxes, i.e. "rectangle", what the "R" in R-tree stands for).

Each node of an R-tree has a variable number of entries (up to some pre-defined maximum). Each entry within a non-leaf node stores two pieces of data: a way of identifying a child node, and the bounding box of all entries within this child node.

The insertion and deletion algorithms use the bounding boxes from the nodes to ensure that "nearby" elements are placed in the same leaf node (in particular, a new element will go into the leaf node that requires the least enlargement in its bounding box). Each entry within a leaf node stores two pieces of information; a way of identifying the actual data element (which, alternatively, may be placed directly in the node), and the bounding box of the data element.

Similarly, the searching algorithms (e.g., intersection, containment, nearest) use the bounding boxes to decide whether or not to search inside a child node. In this way, most of the nodes in the tree are never "touched" during a search. Like B-trees, this makes R-trees suitable for databases, where nodes can be paged to memory when needed.

Different algorithms can be used to split nodes when they become too full, resulting in the quadratic and linear R-tree sub-types.

R-trees do not historically guarantee good worst-case performance, but generally perform well with real-world data.[citation needed] However, a new algorithm was published in 2004 that defines the Priority R-Tree, which claims to be as efficient as the most efficient methods of 2004 and is at the same time worst-case optimal.[1]

When data is organized in an R-Tree, the k nearest neighbors (for any Lp-Norm) of all points can efficiently be computed using a spatial join[2]. This is beneficial for many algorithms based on the k nearest neighbors, for example the Local Outlier Factor.



[edit] Variants

  • R* tree
  • R+ tree
  • Hilbert R-tree
  • Priority R-Tree (PR-Tree) - The PR-tree performs similarly to the best known R-tree variants on real-life and relatively evenly distributed data, but outperforms them significantly on more extreme data.[1]

[edit] Algorithm

[edit] Search

The input is a search rectangle (Query box). Searching is quite similar to searching in a B+tree. The search starts from the root node of the tree. Every internal node contains a set of rectangles and pointers to the corresponding child node and every leaf node contains the rectangles of spatial objects (the pointer to some spatial object can be there). For every rectangle in a node, it has to be decided if it overlaps the search rectangle or not. If yes, the corresponding child node has to be searched also. Searching is done like this in a recursive manner until all overlapping nodes have been traversed. When a leaf node is reached, the contained bounding boxes (rectangles) are tested against the search rectangle and their objects (if there are any) are put into the result set if they lie within the search rectangle.

[edit] Insertion

To insert an object, the tree is traversed recursively from the root node. All rectangles in the current internal node are examined. The constraint of least coverage is employed to insert an object, i.e., the box that needs least enlargement to enclose the new object is selected. In the case where there is more than one rectangle that meets this criterion, the one with the smallest area is chosen. Inserting continues recursively in the chosen node. Once a leaf node is reached, a straightforward insertion is made if the leaf node is not full. If the leaf node is full, it must be split before the insertion is made. A few splitting algorithms have been proposed for good R-tree performance.

[edit] Bulk-loading

  • Sort-Tile-Recursive (STR) [3]
  • Packed Hilbert R-Tree - Uses the Hilbert value of the center of a rectangle to sort the leaf nodes and recursively builds the tree.
  • Nearest-X - Rectangles are sorted on the x-coordinate and nodes are created.

[edit] See also

[edit] References

  1. ^ a b Lars Arge, Mark de Berg, Herman J. Haverkort, Ke Yi: ""The Priority R-Tree: A Practically Efficient and Worst-Case Optimal RTree"", SIGMOD 2004, June 13–18, Paris, France
  2. ^ Brinkhoff, T.; Kriegel, H. P.; Seeger, B. (1993). "Efficient processing of spatial joins using R-trees". ACM SIGMOD Record 22: 237. doi:10.1145/170036.170075edit
  3. ^ Scott T. Leutenegger, Jeffrey M. Edgington and Mario A. Lopez: STR: A Simple and Efficient Algorithm for R-Tree Packing

[edit] External links

posted @ 2010-12-01 11:46 JonsenElizee 阅读(2477) | 评论 (0)编辑 收藏

2010年11月29日 #

简介: 整合 Apache Http Server 和 Tomcat 可以提升对静态文件的处理性能、利用 Web 服务器来做负载均衡以及容错、无缝的升级应用程序。本文介绍了三种整合 Apache 和 Tomcat 的方式

Author LiuDong

首先我们先介绍一下为什么要让 Apache 与 Tomcat 之间进行连接。事实上 Tomcat 本身已经提供了 HTTP 服务,该服务默认的端口是 8080,装好 tomcat 后通过 8080 端口可以直接使用 Tomcat 所运行的应用程序,你也可以将该端口改为 80。

既然 Tomcat 本身已经可以提供这样的服务,我们为什么还要引入 Apache 或者其他的一些专门的 HTTP 服务器呢?原因有下面几个:

1. 提升对静态文件的处理性能

2. 利用 Web 服务器来做负载均衡以及容错

3. 无缝的升级应用程序

这三点对一个 web 网站来说是非常之重要的,我们希望我们的网站不仅是速度快,而且要稳定,不能因为某个 Tomcat 宕机或者是升级程序导致用户访问不了,而能完成这几个功能的、最好的 HTTP 服务器也就只有 apache 的 http server 了,它跟 tomcat 的结合是最紧密和可靠的。

接下来我们介绍三种方法将 apache 和 tomcat 整合在一起。


这是最常见的方式,你可以在网上找到很多关于配置JK的网页,当然最全的还是其官方所提供的文档。JK 本身有两个版本分别是 1 和 2,目前 1 最新的版本是 1.2.19,而版本 2 早已经废弃了,以后不再有新版本的推出了,所以建议你采用版本 1。

JK 是通过 AJP 协议与 Tomcat 服务器进行通讯的,Tomcat 默认的 AJP Connector 的端口是 8009。JK 本身提供了一个监控以及管理的页面 jkstatus,通过 jkstatus 可以监控 JK 目前的工作状态以及对到 tomcat 的连接进行设置,如下图所示:

图 1:监控以及管理的页面 jkstatus
图 1:监控以及管理的页面 jkstatus

在这个图中我们可以看到当前JK配了两个连接分别到 8109 和 8209 端口上,目前 s2 这个连接是停止状态,而 s1 这个连接自上次重启后已经处理了 47 万多个请求,流量达到 6.2 个 G,最大的并发数有 13 等等。我们也可以利用 jkstatus 的管理功能来切换 JK 到不同的 Tomcat 上,例如将 s2 启用,并停用 s1,这个在更新应用程序的时候非常有用,而且整个切换过程对用户来说是透明的,也就达到了无缝升级的目的。关于 JK 的配置文章网上已经非常多了,这里我们不再详细的介绍整个配置过程,但我要讲一下配置的思路,只要明白了配置的思路,JK 就是一个非常灵活的组件。

JK 的配置最关键的有三个文件,分别是

Apache 服务器的配置文件,用来加载 JK 模块以及指定 JK 配置文件信息
到 Tomcat 服务器的连接定义文件
URI 映射文件,用来指定哪些 URL 由 Tomcat 处理,你也可以直接在 httpd.conf 中配置这些 URI,但是独立这些配置的好处是 JK 模块会定期更新该文件的内容,使得我们修改配置的时候无需重新启动 Apache 服务器。

其中第二、三个配置文件名都可以自定义。下面是一个典型的 httpd.conf 对 JK 的配置

# (httpd.conf)
# 加载 mod_jk 模块
LoadModule jk_module modules/

# Configure mod_jk

JkWorkersFile conf/
JkMountFile conf/
JkLogFile logs/mod_jk.log
JkLogLevel warn

接下来我们在 Apache 的 conf 目录下新建两个文件分别是、。这两个文件的内容大概如下


# list the workers by name

worker.list=DLOG4J, status

# localhost server 1
# ------------------------

# localhost server 2
# ------------------------

worker.DLOG4J.balanced_workers=s1, s2


以上的 配置就是我们前面那个屏幕抓图的页面所用的配置。首先我们配置了两个类型为 ajp13 的 worker 分别是 s1 和 s2,它们指向同一台服务器上运行在两个不同端口 8109 和 8209 的 Tomcat 上。接下来我们配置了一个类型为 lb(也就是负载均衡的意思)的 worker,它的名字是 DLOG4J,这是一个逻辑的 worker,它用来管理前面配置的两个物理连接 s1 和 s2。最后还配置了一个类型为 status 的 worker,这是用来监控 JK 本身的模块。有了这三个 worker 还不够,我们还需要告诉 JK,哪些 worker 是可用的,所以就有 worker.list = DLOG4J, status 这行配置。

接下来便是 URI 的映射配置了,我们需要指定哪些链接是由 Tomcat 处理的,哪些是由 Apache 直接处理的,看看下面这个文件你就能明白其中配置的意义



相信你已经明白了一大半了:所有的请求都由 DLOG4J 这个 worker 进行处理,但是有几个例外,/jkstatus 请求由 status 这个 worker 处理。另外这个配置中每一行数据前面的感叹号是什么意思呢?感叹号表示接下来的 URI 不要由 JK 进行处理,也就是 Apache 直接处理所有的图片、css 文件、js 文件以及静态 html 文本文件。

通过对 和 的配置,可以有各种各样的组合来满足我们前面提出对一个 web 网站的要求。您不妨动手试试!



这是利用 Apache 自带的 mod_proxy 模块使用代理技术来连接 Tomcat。在配置之前请确保是否使用的是 2.2.x 版本的 Apache 服务器。因为 2.2.x 版本对这个模块进行了重写,大大的增强了其功能和稳定性。

http_proxy 模式是基于 HTTP 协议的代理,因此它要求 Tomcat 必须提供 HTTP 服务,也就是说必须启用 Tomcat 的 HTTP Connector。一个最简单的配置如下

ProxyPass /images !
ProxyPass /css !
ProxyPass /js !
ProxyPass / http://localhost:8080/

在这个配置中,我们把所有 http://localhost 的请求代理到 http://localhost:8080/ ,这也就是 Tomcat 的访问地址,除了 images、css、js 几个目录除外。我们同样可以利用 mod_proxy 来做负载均衡,再看看下面这个配置

ProxyPass /images !
ProxyPass /css !
ProxyPass /js !

ProxyPass / balancer://example/
<Proxy balancer://example/>
BalancerMember http://server1:8080/
BalancerMember http://server2:8080/
BalancerMember http://server3:8080/

配置比 JK 简单多了,而且它也可以通过一个页面来监控集群运行的状态,并做一些简单的维护设置。

图 2:监控集群运行状态
图 2:监控集群运行状态



ajp_proxy 连接方式其实跟 http_proxy 方式一样,都是由 mod_proxy 所提供的功能。配置也是一样,只需要把 http:// 换成 ajp:// ,同时连接的是 Tomcat 的 AJP Connector 所在的端口。上面例子的配置可以改为:

ProxyPass /images !
ProxyPass /css !
ProxyPass /js !

ProxyPass / balancer://example/
<Proxy balancer://example/>
BalancerMember ajp://server1:8080/
BalancerMember ajp://server2:8080/
BalancerMember ajp://server3:8080/

采用 proxy 的连接方式,需要在 Apache 上加载所需的模块,mod_proxy 相关的模块有、、、、, 其中 只在 Apache 2.2.x 中才有。如果是采用 http_proxy 方式则需要加载 和;如果是 ajp_proxy 则需要加载 和 mod_proxy_ajp.so这两个模块。



相对于 JK 的连接方式,后两种在配置上是比较简单的,灵活性方面也一点都不逊色。但就稳定性而言就不像 JK 这样久经考验,毕竟 Apache 2.2.3 推出的时间并不长,采用这种连接方式的网站还不多,因此,如果是应用于关键的互联网网站,还是建议采用 JK 的连接方式。



posted @ 2010-11-29 13:07 JonsenElizee 阅读(408) | 评论 (0)编辑 收藏

2010年11月25日 #

Look for this kind of nice player long long time.
It's promoted by "QianLiBingFeng" and completed at 2008/08/02 with continuing mantenance on google code web site:

posted @ 2010-11-25 11:44 JonsenElizee 阅读(203) | 评论 (0)编辑 收藏

2010年11月12日 #


posted @ 2010-11-12 20:04 JonsenElizee 阅读(240) | 评论 (0)编辑 收藏

2010年11月10日 #

save this line as a url:

posted @ 2010-11-10 08:54 JonsenElizee 阅读(232) | 评论 (0)编辑 收藏

2010年11月9日 #

Assembly Language for x86 Processors, 6th edition
Book cover

by Kip Irvine, Florida International University


ISBN: 0-13-602212-X

Published by: Prentice-Hall (Pearson Education), February 2010

Visit the Web site for the Fifth Edition  
Bookmark this Web Site  
Picture of Kip Irvine
Online Resources ( Getting started with MASM Chapter objectives
International Editions   Sample chapters and videos   Instructor resources
Buy at or   Debugging tools   Discussion group (
    Link libraries and example programs   Supplemental files
Links to Assembly Language sites   Articles    
Assembly language workbook   Bug reports  

New feature! This edition offers recorded videos by the author, working through solutions to selected programming exercises.
Thanks to James Brink, Gerald Cahill, David Topham, and W.A. Barrett. John Taylor is the offical corrections manager.

Copyright 2010 Kip Irvine. All rights reserved.
posted @ 2010-11-09 15:03 JonsenElizee 阅读(384) | 评论 (0)编辑 收藏

2010年11月4日 #

     摘要: [Top] [Contents] [Index] [ ? ] Bash Reference Manual This text is a brief description of the features that are present in the Bash shell. ...  阅读全文
posted @ 2010-11-04 23:06 JonsenElizee 阅读(542) | 评论 (0)编辑 收藏


sed -- invoke the stream editor


sed [ -n ] [ script ] [ -f sfile ] [ file ... ]

sed [ -n ] [ -e script ] ... [ -f sfile ] ... [ file ... ]


The sed command copies the named files (standard input default) to the standard output, edited according to a script of commands.

sed takes the following options:

-e script
Read the command script; usually quoted to protect it from the shell.
-f sfile
Take the script from the file sfile; these options accumulate. If there is just one -e option and no -f options, the flag -e may be omitted.
Suppress the default output.
A script consists of editing commands, one per line, of the following form:

[ address [ , address ] ] function [ arguments ]

In normal operation, sed cyclically copies a line of input into a pattern space (unless there is something left after a D command), applies in sequence all commands whose addresses select that pattern space, and at the end of the script copies the pattern space to the standard output (except under -n) and deletes the pattern space.

A semicolon ``;'' can be used as a command delimiter.

Some of the commands use a hold space to save all or part of the pattern space for subsequent retrieval (see the ``Limitations'' section).

An address is either a decimal number that counts input lines cumulatively across files, a ``$'' that addresses the last line of input, or a context address, that is, a /regular expression/ as described in regexp(M), modified as follows:

  • In a context address, the construction \?regular expression?, where ``?'' is any character, is identical to /regular expression/. Note that in the context address \xabc\xdefx, the second x stands for itself, so that the standard expression is abcxdef.
  • The escape sequence \n matches a newline embedded in the pattern space.
  • A dot (.) matches any character except the terminal newline of the pattern space.
  • A command line with no addresses selects every pattern space.
  • A command line with one address selects each pattern space that matches the address.
  • A command line with two addresses separated by a comma selects the inclusive range from the first pattern space that matches the first address through the next pattern space that matches the second. (If the second address is a number less than or equal to the line number first selected, only one line is selected.) Thereafter, the process is repeated, looking again for the first address.
Editing commands can be applied only to nonselected pattern spaces by use of the negation function ``!'' described in the next section.


In the following list of functions, the maximum number of permissible addresses for each function is indicated in parentheses.

The text argument consists of one or more lines, all but the last of which end with backslashes to hide the newlines. Backslashes in text are treated like backslashes in the replacement string of an s command, and may be used to protect initial blanks and tabs against the stripping that is done on every script line.

The rfile or wfile argument must terminate the command line and must be preceded by one blank. Each wfile is created before processing begins. There can be at most 10 distinct wfile arguments.

(1) a\
Appends text, placing it on the output before reading the next input line. Note that there must be a line break between the command and the text.
(2) b label
Branches to the : command bearing the label. If label is empty, branches to the end of the script.
(2) c\
Changes text by deleting the pattern space and then appending text. With 0 or 1 address or at the end of a 2-address range, places text on the output and starts the next cycle. Note that there must be a line break between the command and the text.
(2) d
Deletes the pattern space and starts the next cycle.
(2) D
Deletes the initial segment of the pattern space through the first newline and starts the next cycle.
(2) g
Replaces the contents of the pattern space with the contents of the hold space.
(2) G
Appends the contents of the hold space to the pattern space.
(2) h
Replaces the contents of the hold space with the contents of the pattern space.
(2) H
Appends the contents of the pattern space to the hold space.
(1) i\
Insert. Places text on the standard output. Note that there must be a line break between the command and the text.
(2) l
Lists the pattern space on the standard output in an unambiguous way. Nonprinting characters are displayed as a three digit octal number preceded by a backslash ``\''. The following characters are printed as escape sequences:
Character Output
backslash \\
alert (bell) \a
backspace \b
form feed \f
carriage return \r
horizontal tab \t
vertical tab \v
Any output lines that are longer than the output device width (determined by the environment variable COLUMNS) are folded into multiple lines. New lines, inserted when folding a long line, are escaped by a preceding backslash character. The ends of each line in the pattern space are denoted by a dollar character ``$''.
(2) n
Copies the pattern space to the standard output. Replaces the pattern space with the next line of input.
(2) N
Appends the next line of input to the pattern space with an embedded newline. (The current line number changes.)
(2) p
Prints (copies) the pattern space on the standard output.
(2) P
Prints (copies) the initial segment of the pattern space through the first newline to the standard output.
(1) q
Quits sed by branching to the end of the script. No new cycle is started.
(2) r rfile
Reads the contents of rfile and places them on the output before reading the next input line.
(2) s /regular expression/replacement/flags
Substitutes the replacement string for instances of the regular expression in the pattern space. Any character may be used instead of ``/''. For a more detailed description, see regexp(M).

Flags is zero or more of:

Substitute for just the nth occurrence of the regular expression. n must be an integer greater than zero.
Globally substitutes for all non-overlapping instances of the regular expression rather than just the first one.
Prints the pattern space if a replacement was made.
w wfile
Writes the pattern space to wfile if a replacement was made.
(2) t label
Branches to the colon (:) command bearing label if any substitutions have been made since the most recent reading of an input line or execution of a t command. If label is empty, t branches to the end of the script.
(2) w wfile
Writes the pattern space to wfile.
(2) x
Exchanges the contents of the pattern and hold spaces.
(2) y /string1/string2/
Replaces all occurrences of characters in string1 with the corresponding characters in string2. The lengths of string1 and string2 must be equal.
(2) ! function
Applies the function (or group, if function is ``{'') only to lines not selected by the address(es).
(0) : label
This command does nothing; it bears a label for b and t commands to branch to. Labels can be at most 8 characters long.
(1) =
Places the current line number on the standard output as a line.
(2) {
Executes the following commands through a matching ``}'' only when the pattern space is selected.
(2) !{
Executes the following commands through a matching ``}'' only when the pattern space is not selected.
An empty command is ignored.
(0) #
Ignore the remainder of the line if # is followed by any other character than ``n'' (treat the line as a comment); if the character ``n'' follows #, suppress the default output (equivalent to the command line option -n).

Environment variables

The width of the standard output device in characters; used by the l command for folding long lines. If this variable is not set or it has an invalid value, sed uses the default value 72.

Exit values

sed continues to process all file arguments even if one or more of them produces an open error. If there is an open error, sed will exit with a value of 1 when it has finished processing the files. A value of 2 indicates a usage error.


The following examples assume the use of sh(C) or ksh(C).

A common use of sed is to edit a file from within a shell script. In this example, every occurrence of the string ``sysman'' in the file infile is replaced by ``System Manager''. A temporary file TMP is used to hold the intermediate result of the edit:

sed -e 's/sysman/System Manager/g' < infile > $TMP
mv $TMP infile
In this example, sed removes all blank lines (including those with just <Tab> and <Space> characters) from padded_file:
   sed '
/^$/ d
/^[<Tab><Space>]*$/ d
´ padded_file
sed can be used to strip all lines from a file which do not contain a certain string. In this example, all lines in the file infile which start with a hash ``#'' are echoed to the screen:

sed -e '/^#/!d' < infile

If several editing commands must be carried out on a file, but the parameters for the edit are to be supplied by the user, then use echo to append command lines to a sed script. The following example removes all occurrences of the strings given as arguments to the script from the file infile. The name of the temporary file is held by the variable SCRIPT:


for name in $*
echo "s/${name}//g" >> $SCRIPT


sed -f $SCRIPT < infile > $TMPFILE

mv $TMPFILE infile


Another use of sed is to process the output from other commands. Here the ps command is filtered using sed to report the status of all processes other than those owned by the super user:

ps -ef | sed -e '/^[<Space><Tab>]*root/d'


Both the hold space and pattern space can hold a maximum of 8192 bytes.

See also

awk(C), ed(C), grep(C), regexp(M)

Chapter 14, ``Manipulating text with sed'' in the Operating System User's Guide

Standards conformance

sed is conformant with:

ISO/IEC DIS 9945-2:1992, Information technology - Portable Operating System Interface (POSIX) - Part 2: Shell and Utilities (IEEE Std 1003.2-1992);
AT&T SVID Issue 2;
X/Open CAE Specification, Commands and Utilities, Issue 4, 1992.

SCO OpenServer Release 5.0.6 -- 1 August 2000

posted @ 2010-11-04 23:02 JonsenElizee 阅读(481) | 评论 (0)编辑 收藏

The C Library Reference Guide

by Eric Huss
© Copyright 1997 Eric Huss

Release 1


1. Language
1.1 Characters
1.1.1 Trigraph Characters
1.1.2 Escape Sequences
1.2 Identifiers
1.2.1 Keywords
1.2.2 Variables
1.2.3 Enumerated Tags
1.2.4 Arrays
1.2.5 Structures and Unions
1.2.6 Constants
1.2.7 Strings
1.2.8 sizeof Keyword
1.3 Functions
1.3.1 Definition
1.3.2 Program Startup
1.4 References
1.4.1 Pointers and the Address Operator
1.4.2 Typecasting
1.5 Operators
1.5.1 Postfix
1.5.2 Unary and Prefix
1.5.3 Normal
1.5.4 Boolean
1.5.5 Assignment
1.5.6 Precedence
1.6 Statements
1.6.1 if
1.6.2 switch
1.6.3 while
1.6.4 do
1.6.5 for
1.6.6 goto
1.6.7 continue
1.6.8 break
1.6.9 return
1.7 Preprocessing Directives
1.7.1 #if, #elif, #else, #endif
1.7.2 #define, #undef, #ifdef, #ifndef
1.7.3 #include
1.7.4 #line
1.7.5 #error
1.7.6 #pragma
1.7.7 Predefined Macros
2. Library
2.1 assert.h
2.1.1 assert
2.2 ctype.h
2.2.1 is... Functions
2.2.2 to... Functions
2.3 errno.h
2.3.1 EDOM
2.3.2 ERANGE
2.3.3 errno
2.4 float.h
2.4.1 Defined Values
2.5 limits.h
2.5.1 Defined Values
2.6 locale.h
2.6.1 Variables and Definitions
2.6.2 setlocale
2.6.3 localeconv
2.7 math.h
2.7.1 Error Conditions
2.7.2 Trigonometric Functions acos asin atan atan2 cos cosh sin sinh tan tanh
2.7.3 Exponential, Logarithmic, and Power Functions exp frexp ldexp log log10 modf pow sqrt
2.7.4 Other Math Functions ceil fabs floor fmod
2.8 setjmp.h
2.8.1 Variables and Definitions
2.8.2 setjmp
2.8.3 longjmp
2.9 signal.h
2.9.1 Variables and Definitions
2.9.2 signal
2.9.3 raise
2.10 stdarg.h
2.10.1 Variables and Definitions
2.10.2 va_start
2.10.3 va_arg
2.10.4 va_end
2.11 stddef.h
2.11.1 Variables and Definitions
2.12 stdio.h
2.12.1 Variables and Definitions
2.12.2 Streams and Files
2.12.3 File Functions clearerr fclose feof ferror fflush fgetpos fopen fread freopen fseek fsetpos ftell fwrite remove rename rewind setbuf setvbuf tmpfile tmpnam
2.12.4 Formatted I/O Functions ...printf Functions ...scanf Functions
2.12.5 Character I/O Functions fgetc fgets fputc fputs getc getchar gets putc putchar puts ungetc
2.12.7 Error Functions perror
2.13 stdlib.h
2.13.1 Variables and Definitions
2.13.2 String Functions atof atoi atol strtod strtol strtoul
2.13.3 Memory Functions calloc free malloc realloc
2.13.4 Environment Functions abort atexit exit getenv system
2.13.5 Searching and Sorting Functions bsearch qsort
2.13.6 Math Functions abs div labs ldiv rand srand
2.13.7 Multibyte Functions mblen mbstowcs mbtowc wcstombs wctomb
2.14 string.h
2.14.1 Variables and Definitions
2.14.2 memchr
2.14.3 memcmp
2.14.4 memcpy
2.14.5 memmove
2.14.6 memset
2.14.7 strcat
2.14.8 strncat
2.14.9 strchr
2.14.10 strcmp
2.14.11 strncmp
2.14.12 strcoll
2.14.13 strcpy
2.14.14 strncpy
2.14.15 strcspn
2.14.16 strerror
2.14.17 strlen
2.14.18 strpbrk
2.14.19 strrchr
2.14.20 strspn
2.14.21 strstr
2.14.22 strtok
2.14.23 strxfrm
2.15 time.h
2.15.1 Variables and Definitions
2.15.2 asctime
2.15.3 clock
2.15.4 ctime
2.15.5 difftime
2.15.6 gmtime
2.15.7 localtime
2.15.8 mktime
2.15.9 strftime
2.15.10 time
Appendix A

Questions, comments, or error reports? Please send them to Eric Huss
posted @ 2010-11-04 22:50 JonsenElizee 阅读(237) | 评论 (0)编辑 收藏

int greatest_common_factor( unsigned int M, unsigned int N ){
int Rem;
while( N > 0 ){
= M % N;
= N;
= Rem;

return M; 

int main() 
int temp;  
int a,b; 
"the greatest common factor of %d and %d is ",a,b);
return getchar();
this is a demo from ischarles.
posted @ 2010-11-04 14:48 JonsenElizee 阅读(212) | 评论 (0)编辑 收藏

long long pow(int x, unsigned int n)
long long p = 1;
while (n > 0) {
if (n & 1) p *= x;
*= x;
>>= 1;        
return p;

//this is a demo from micheal

posted @ 2010-11-04 14:35 JonsenElizee 阅读(274) | 评论 (0)编辑 收藏

2010年11月1日 #

     摘要:   addNavigation() ...  阅读全文
posted @ 2010-11-01 14:20 JonsenElizee 阅读(1254) | 评论 (0)编辑 收藏

2010年10月29日 #

There are y ball with a bad one between them.
all the ball are the same look.
now, give you a balance, how many times do you need to pick out the bad one?

My resolution: need Ball(y) times to pick out the bad one.

#include <stdio.h>

int Ball(int y)
if(y <= 3return 1;
return 1+Ball( y/3 * 3 == y ? y/3 : y/3 +1 );
int main()
int i = 0;
for(i = 2; i < 200; i++) {
"Ball(%3d)=%d \t", i, Ball(i));
if(i%5 == 0) puts("");
return 0;

posted @ 2010-10-29 09:21 JonsenElizee 阅读(1371) | 评论 (0)编辑 收藏

2010年10月28日 #


/* this program should find out the median(s) in N(logN)/(logB) no matter there
/* is duplicated data or not.
/* with memory limitation: 4MB memory available. in fact, it can work on 1MB.
/* I would like to express the idea with code.
/* here is just the pseudocode with out any optimization for easy understanding.
/* maybe, there is no need to check sum == N/2 or N/2+1, but this will get the 
/* median(s) as soon as possible with out more recursive invoking.
/* sorry for any logical problem. please let me know if you found any.

int N = 100000000;// total data number is N
int B = 1000000;  // number of buckets.
int min, max;
scan data from 
0 to N-1 get min and max; // O(N);

// num the data number that is less than min
// min the minimum data in the target data range to find median(s)
// max the maximum data in the target data range to find median(s)
void find_median(int num=0int min, int max)
if(min == max) {
if(N%2) {
            print medians are min and max;
else print median is min; // show you the result
        return// exit

// count all the data in O(N)
int m = max-min > B ? ((max-min)%B ? (max-min)/B + 1 : (max-min)/B)1;
int cnt[B] = {0}; // count the data read.
    while(!EOF) {
int data = read_data()-min;
        // count data in this range [min, max]
        // data/m will get the position of data to increase the cnt[?] value
if(data >= min && data <= max) cnt[data/m]++;
int sum = num, median_1, median_2, i = 0;
while(sum < N/2) sum += cnt[i++];
--// median is in the range of [i*m, (i+1)*m-1]

/* get median(s) when sum is N/2 */
if(sum == N/2) {
if(N%2) { // N is even and there are two medians.
            median_1 = (i+2)*m-1;
= i*m;
while(!EOF) {
int data = read_data()-min;
if(data/== i) {
= (data > median_2 ? data : median_2);
if(data/== i+1) {
= (data < median_1 ? data : median_1);
            pintf medians are median_1 and median_2;
else { // N is an odd number and there is one median.
            median_1 = (i+2)*m-1;
while(!EOF) {
int data = read_data();
if(data/== i+1) median_1 = (data < median_1 ? data : median_1);
            print median 
is median_1;

/* get median(s) when sum is N/2+1 */
if(sum == N/2+1) {
if(N%2) { // N is even and there are two medians.
            median_1 = i*m;
= i*m;
while(!EOF) {
int data = read_data();
if(data/== i) {
= max;
= (data > median_2 ? data : median_2);
            pintf medians are median_1 and median_2;
else {
= i*m; // get (N/2+1)th data.
            while(!EOF) {
int data = read_data();
if(data/== i) median_2 = (data > median_2 ? data : median_2);
            print median 
is median_2;

// if sum is not N/2 or (N/2 + 1), recursively to find out the median(s)
= (i+1)*m-1;
= i*m;
// get min and max for next processing
int data = read_data()-min;
if(data/== i)
= (data < min ? data : min);
= (data > max ? data : max);
    find_median(sum, min, max);

posted @ 2010-10-28 16:39 JonsenElizee 阅读(1532) | 评论 (0)编辑 收藏

2010年10月27日 #

ISSUE: 输入上百万个行星的位置, 求距离第K近的两个行星。

1. star field simulation graph is planar.
2. the coordinate of star is (x, y) that is treated as a point。
3. N = 1000000

1. bucket-sort all points according to x-coordinate. get B buckets.
this is will completed in O(NlogN).
struct bucket {
int num;       // number of points in this bucket.
    point* points; // points in this bucket.
    double x;      // value of x-coordinate.
// B buckets got.

struct distance {
    point p1;
    point p2;
double d;     // distance between p1 and p2.

   distance kdis[K]; 
// to record K small distance. and it's a eliminating-tree.
   kdis[0 to K-1= 0;

for(i = [0, B-2]) // O(B)
// check bck[i] and bck[i+1]
    if(bck[i+1].x - bck[i].x >= kdis[K-1].d && kdis[K-1!= 0)
// there is no need to check these two buckets.
continue// save time.

* poi = bck[i].points;
for(j = [0, bck.num-1]) // O(N/B)
        point p 
= poi[j];
        find K points in bck[i+1] near to p
        with binary searching method 
        according to p.y.
// K points got in bck[i+1]

for(m = [0, K-1]) // O(K)
            distance tmp 
= get_distance(kp[m], p);
if(tmp.d < kdis[K-1].d)
-1= tmp;
// adjust kdis[K-1], for it's a eliminating tree.

// finally, the kdis[K-1] is the kth distance in this star graph.
// the whole processing will be completed in O(NlogN) + O(B*N/B*K).
// and SC is O(N) + O(K) = O(N).

    find K points in bck[i+1] near to p
    with binary searching method 
    according to p.y.
's not complecated! and could be found in O(log(N/B)).

posted @ 2010-10-27 15:18 JonsenElizee 阅读(1462) | 评论 (0)编辑 收藏

2010年10月24日 #

Here is a simple implementation for this issue. And it's TC is O(n/10), O(n);
Any better one is expected.
 1 int onenumber(int n)
 2 {
 3     if(n <= 0return 0;
 4     if(n <= 9return 1;
 6     int bak = n, hig = 1, num = 0;
 7     while(n >= 10) {
 8         hig *= 10;
 9         n /= 10;
10     }
12     if(n == 1) {
13         num = bak-hig+1 + ((bak-hig == 0? 0 : (bak-hig <= 9 ? 1 : onenumber(bak-hig)));
14         num += (hig-1 <= 9 ? 1 : onenumber(hig-1));
15     }
16     else {
17         num = (bak - n*hig == 0 ? 0 : (bak - n*hig <= 9 ? 1 : onenumber(bak - n*hig)));
18         num += (n*hig-1 <= 9 ? 1 : onenumber(n*hig-1));
19     }
21     return num;
22 }

posted @ 2010-10-24 19:04 JonsenElizee 阅读(1269) | 评论 (0)编辑 收藏

Refer Find kth number in O(n) TC

include <stdio.h>
#include <stdlib.h>
#include <time.h>

#define N 20

void init_a(int A[])
  int i = 0;
    A[i] = rand()%100;

void print_array(int A[])
   int i = 0;

void swap(int* a, int* b)
   int tmp = *a;
   *a = *b;
   *b = tmp;

int rand_partition(int A[], int start, int end)
   int i = start-1;
   int j = start;
   int num = rand()%(end-start+1)+start;
   int x = A[end];

   return i+1;

int random_select(int A[], int start, int end, int k)
  int i = 0;
  if(start == end)
    return A[start];
  int q = rand_partition(A, start, end);
   i = q-start+1;
  if(i == k)
    return A[q];
  else if(i<k)
    return random_select( A, q+1, end, k-i);
    return random_select( A, start, q-1, k);

void quick_sort(int A[], int start, int end)
     int q = rand_partition(A, start, end);
      quick_sort( A, q+1, end);
      quick_sort( A, start, q-1);
int main(int argc, char *argv[])
  int A[N];
  int num = 0;
  int res = 0;
   num = rand()%(N-10)+5;
  printf("we begin select %d minimun number\n",num);
   res = random_select( A, 0 , N-1, num);
  printf("and num is %d\n",res);
   quick_sort( A, 0 , N-1);
  printf("after quick sort the array is:\n");
  return 0;
posted @ 2010-10-24 01:17 JonsenElizee| 编辑 收藏

2010年10月22日 #

there is a car near to a desert with width of 563Km.
and there is a gas station at the left border of the desert.
the car could take 315L gas at most one time.
it can store the gas in the desert for a longer trip.
now, how much gas it need at least to go through the desert?
from the internet, I got a answer 1575. but it's not 1575 in my analysis.

posted @ 2010-10-22 16:46 JonsenElizee| 编辑 收藏

Debugging Programs with Multiple Threads

In some operating systems, such as HP-UX and Solaris, a single program may have more
than one thread of execution. The precise semantics of threads differ from one operating
system to another, but in general the threads of a single program are akin to multiple
processes—except that they share one address space (that is, they can all examine and
modify the same variables). On the other hand, each thread has its own registers and
execution stack, and perhaps private memory.
gdb provides these facilities for debugging multi-thread programs:
• automatic notification of new threads
• ‘thread threadno’, a command to switch among threads
• ‘info threads’, a command to inquire about existing threads
• ‘thread apply [threadno] [all] args’, a command to apply a command to a list of
• thread-specific breakpoints
• ‘set print thread-events’, which controls printing of messages on thread start and
• ‘set libthread-db-search-path path’, which lets the user specify which libthread_
db to use if the default choice isn’t compatible with the program.
Warning: These facilities are not yet available on every gdb configuration
where the operating system supports threads. If your gdb does not support
threads, these commands have no effect. For example, a system without thread
support shows no output from ‘info threads’, and always rejects the thread
command, like this:
(gdb) info threads
(gdb) thread 1
Thread ID 1 not known. Use the "info threads" command to
see the IDs of currently known threads.
The gdb thread debugging facility allows you to observe all threads while your program
runs—but whenever gdb takes control, one thread in particular is always the focus of
debugging. This thread is called the current thread. Debugging commands show program
information from the perspective of the current thread.
like ‘process 368’, with no further qualifier.
For debugging purposes, gdb associates its own thread number—always a single
integer—with each thread in your program.
info threads
Display a summary of all threads currently in your program. gdb displays for
each thread (in this order):
1. the thread number assigned by gdb
2. the target system’s thread identifier (systag)
3. the current stack frame summary for that thread
An asterisk ‘*’ to the left of the gdb thread number indicates the current thread.
For example,
(gdb) info threads
3 process 35 thread 27 0x34e5 in sigpause ()
2 process 35 thread 23 0x34e5 in sigpause ()
* 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
at threadtest.c:68
On HP-UX systems:
For debugging purposes, gdb associates its own thread number—a small integer assigned
in thread-creation order—with each thread in your program.
Whenever gdb detects a new thread in your program, it displays both gdb’s thread
number and the target system’s identification for the thread with a message in the form
‘[New systag]’. systag is a thread identifier whose form varies depending on the particular
system. For example, on HP-UX, you see
[New thread 2 (system thread 26594)]
when gdb notices a new thread.
info threads
Display a summary of all threads currently in your program. gdb displays for
each thread (in this order):
1. the thread number assigned by gdb
2. the target system’s thread identifier (systag)
3. the current stack frame summary for that thread
An asterisk ‘*’ to the left of the gdb thread number indicates the current thread.
For example,
(gdb) info threads
* 3 system thread 26607 worker (wptr=0x7b09c318 "@") \
at quicksort.c:137
2 system thread 26606 0x7b0030d8 in __ksleep () \
from /usr/lib/libc.2
1 system thread 27905 0x7b003498 in _brk () \
from /usr/lib/libc.2
On Solaris, you can display more information about user threads with a Solaris-specific
maint info sol-threads
Display info on Solaris user threads.
thread threadno
Make thread number threadno the current thread. The command argument
threadno is the internal gdb thread number, as shown in the first field of the
‘info threads’ display. gdb responds by displaying the system identifier of the
thread you selected, and its current stack frame summary:
(gdb) thread 2
[Switching to process 35 thread 23]
0x34e5 in sigpause ()
As with the ‘[New ...]’ message, the form of the text after ‘Switching to’
depends on your system’s conventions for identifying threads.
The debugger convenience variable ‘$_thread’ contains the number of the current
thread. You may find this useful in writing breakpoint conditional expressions,
command scripts, and so forth. See See hundefinedi [Convenience
Variables], page hundefinedi, for general information on convenience variables.
thread apply [threadno] [all] command
The thread apply command allows you to apply the named command to one
or more threads. Specify the numbers of the threads that you want affected
with the command argument threadno. It can be a single thread number, one
of the numbers shown in the first field of the ‘info threads’ display; or it could
be a range of thread numbers, as in 2-4. To apply a command to all threads,
type thread apply all command.
set print thread-events
set print thread-events on
set print thread-events off
The set print thread-events command allows you to enable or disable printing
of messages when gdb notices that new threads have started or that threads
have exited. By default, these messages will be printed if detection of these
events is supported by the target. Note that these messages cannot be disabled
on all targets.
show print thread-events
Show whether messages will be printed when gdb detects that threads have
started and exited.
See hundefinedi [Stopping and Starting Multi-thread Programs], page hundefinedi, for
more information about how gdb behaves when you stop and start programs with multiple
See hundefinedi [Setting Watchpoints], page hundefinedi, for information about watchpoints
in programs with multiple threads.
set libthread-db-search-path [path]
If this variable is set, path is a colon-separated list of directories gdb will use
to search for libthread_db. If you omit path, ‘libthread-db-search-path’
will be reset to an empty list.
On gnu/Linux and Solaris systems, gdb uses a “helper” libthread_db library
to obtain information about threads in the inferior process. gdb will
use ‘libthread-db-search-path’ to find libthread_db. If that fails, gdb will
continue with default system shared library directories, and finally the directory
from which libpthread was loaded in the inferior process.
For any libthread_db library gdb finds in above directories, gdb attempts
to initialize it with the current inferior process. If this initialization fails
(which could happen because of a version mismatch between libthread_db
and libpthread), gdb will unload libthread_db, and continue with the next
directory. If none of libthread_db libraries initialize successfully, gdb will
issue a warning and thread debugging will be disabled.
Setting libthread-db-search-path is currently implemented only on some
show libthread-db-search-path
Display current libthread db search path.

posted @ 2010-10-22 13:09 JonsenElizee 阅读(557) | 评论 (0)编辑 收藏

This is a funny programm and I don't why it happens in this way.
No matter what data input that is composed with different numbers, like 123456,
124578, 235689, 789456, 147896, 321478 and so on. through this program, it will
get a same data ever got.

  1 // funny program by JonsenElizee.
  2 //
  4 #include "stdafx.h"
  5 #include <math.h>
  6 #include <assert.h>
  7 /*
  8  * set value in specified position.
  9  * void* ptr pointer of the start point of bit.
 10  * int pos position of the bit to be set and pos starts from 0.
 11  * int val value to set. val is 0 or 1.
 12  */
 13 void setbit(void* ptr, int pos, int val)
 14 {
 15     /* cast to unsigned char* type pointer */
 16     unsigned char* uch = (unsigned char*)ptr;
 18     /* move pointer */
 19     uch += pos/8;
 21     /* set the bit with right value, 0 or 1. */
 22     unsigned char tmp = 1 << (pos%8);
 23     if ( val && (unsigned char)(*uch & tmp) == 0*uch += tmp;
 24     else *uch -= tmp;
 25 }
 26 unsigned char getbit(void* ptr, int pos) 
 27 {
 28     /* cast to unsigned char* type pointer */
 29     unsigned char* uch = (unsigned char*)ptr;
 31     /* move pointer */
 32     uch += pos/8;
 34     /* set the bit with right value, 0 or 1. */
 35     unsigned char tmp = 1 << (pos%8);
 36     return (unsigned char)(*uch & tmp);
 37 }
 39 unsigned revert_unsigned_int(unsigned ipt)
 40 {
 41     unsigned opt = 0;
 42     unsigned short i = 0;
 43     for(opt = ipt; opt != 0; opt /= 10, i++); 
 44     for(opt = 0; ipt != 0; ipt /= 10)
 45         opt += (ipt - ipt / 10 * 10* ((unsigned)pow(10--i));
 46     return opt;
 47 }
 49 unsigned sort_unsigned_int(unsigned ipt, int ascend)
 50 {
 51     unsigned opt = 0;
 52     unsigned i = 0;
 54     /* get length of input data */
 55     for(opt = ipt; opt != 0; opt /= 10, i++); 
 57     unsigned char* num = (unsigned char *)malloc(i);
 58     memset(num, 0, i);
 59     unsigned char* ptr = num;
 60     unsigned char* mov = ptr + 1;
 61     unsigned n = i;
 63     /* get each number char of input data */
 64     for(; ipt != 0; ipt /= 10)
 65         num[--i] = (unsigned char)(ipt - ipt / 10 * 10);
 67     /* sort the number */
 68     for(i = 0; i < n-1; i ++) {
 69         if(ascend) {
 70             while(mov > num && mov[0< mov[-1]) {
 71                 mov[0^= mov[-1];
 72                 mov[-1^= mov[0];
 73                 mov[0^= mov[-1];
 74                 mov--;
 75             }
 76         } 
 77         else {
 78             while(mov > num && mov[0> mov[-1]) {
 79                 mov[0^= mov[-1];
 80                 mov[-1^= mov[0];
 81                 mov[0^= mov[-1];
 82                 mov--;
 83             }
 84         }
 85         ptr++;
 86         mov = ptr+1;
 87     }
 89     /* convert to a unsigned int */
 90     for (opt = i = 0; i < n; i++)
 91     {
 92         opt += num[i] * ((unsigned)pow(10, n-i-1));
 93     }
 95     free(num);
 96     return opt;
 97 }
 99 void loop_to_original_data(unsigned ipt)
100 {
101     assert(ipt < 1000000);
102     char his[1000000= {0};
103     while(1) {
104         printf("%d ", ipt);
105         unsigned a = sort_unsigned_int(ipt, 1);
106         unsigned b = sort_unsigned_int(ipt, 0);
107         if(a == b) {
108             printf("%d\n", ipt);
109             return;
110         }
111         unsigned rst =  b - a;
112         if (getbit(his, rst)) {
113             printf("%d\n", rst);        
114             break;
115         }
116         else 
117             setbit(his, rst, 1);
118         ipt = rst;
119     }
120 }
122 int main()
123 {
124     loop_to_original_data(123456);
125     getchar();
126     return 0;
127 }

posted @ 2010-10-22 08:55 JonsenElizee 阅读(1387) | 评论 (0)编辑 收藏

2010年10月21日 #

Here is a simple implementation to convert string to 0x string.
Better one is expected ......
 1 #include <assert.h>
 2 /*
 3  * convert string to 0x string.
 4  * 
 5  * const char* ipt input string.
 6  * char* opt output 0x string.
 7  */
 8 void str2Xstr(const char* ipt, char* opt)
 9 {
10     assert(ipt != NULL && opt != NULL);
11     assert(sizeof(char== 1);
13     /* add prefix 0x into opt */
14     *opt++ = '0';
15     *opt++ = 'x';
17     char* bak = opt;
18     while(*ipt != '\0') {
19         /* get the char and cast it to int */
20         char cha = *ipt++;
21         unsigned short tmp = cha;
22         /* assert sizeof char is 1 (8bits) */
23         tmp <<= 8;
24         tmp >>= 12;
25         if(tmp >= 10*opt++ = tmp-10+'A';
26         else *opt++ = tmp+'0';
28         tmp = cha;
29         tmp <<= 12;
30         tmp >>= 12;
31         if(tmp >= 10*opt++ = tmp-10+'A';
32         else *opt++ = tmp+'0';
33     }
34     /* terminate string */
35     *opt = 0;
36 }
38 int main()
39 {
40     char opt[64= {0};
41     str2Xstr("2009-09", opt);
42     puts(opt); /* 0x323030392D3039 */
43     getchar();
44     return 0;
45 }

Using & operation is a better way:
 1 /*
 2  * convert string to 0x string.
 3  * 
 4  * const char* ipt input string.
 5  * char* opt output 0x string.
 6  */
 7 void str2Xstr(const char* ipt, char* opt)
 8 {
 9     assert(ipt != NULL && opt != NULL);
10     assert(sizeof(char== 1);
12     /* add prefix 0x into opt */
13     *opt++ = '0';
14     *opt++ = 'x';
16     char* bak = opt;
17     while(*ipt != '\0') {
18         /* get the char and cast it to int */
19         char cha = *ipt++;
20         unsigned char tmp = cha;
21         /* assert sizeof char is 1 (8bits) */
22         tmp &= '\xF0';
23         tmp >>= 4;
24         *opt++ = tmp >= 10 ? tmp-10+'A' : tmp+'0';
26         tmp = cha;
27         tmp &= '\x0F';
28         *opt++ = tmp >= 10 ? tmp-10+'A' : tmp+'0';
29     }
30     /* terminate string and turn back one step */
31     *opt-- = 0;
32 }

posted @ 2010-10-21 11:40 JonsenElizee 阅读(365) | 评论 (0)编辑 收藏

Here is simple implementation for converting int value to 0x string with out sprintf and so on.
Any better way is expected ......
 1 #include <assert.h>
 2 /*
 3  * convert int value to 0x string.
 4  *
 5  * int ipt input int value.
 6  * char* opt output string.
 7  */
 8 void int2Xstr(int ipt, char* opt)
 9 {
10     assert(ipt != NULL && opt != NULL);
12     /* add prefix "0x" */
13     *opt++ = '0';
14     *opt++ = 'x';
15     opt +=7;
17     /* number of 4bits-unit */
18     int num = sizeof(int)*2;
20     /* using << and >> to get 4bits value and convert it to 0x char */
21     for(int i = 0; i < num; i ++)
22     {
23         /* negative value should be converted to unsigned one */
24         unsigned var = ipt < 0 ? (unsigned)(-ipt) : (unsigned)ipt;
26         /* >> and << to clear other bits */
27         var >>= 4*i;
28         var <<= (num-1)*4;
29         var >>= (num-1)*4;
31         /* convert to 0x char */
32         if(var >= 10) *opt-- = (var - 10+ 'A';
33         else *opt-- = var + '0';
34     }
35 }
36 int main()
37 {
38     char opt[32= {0};
39     int2Xstr(1234567890, opt);
40     puts(opt); /* 0x499602D2 */
41     getchar();
42     return 0;
43 }

posted @ 2010-10-21 10:24 JonsenElizee 阅读(311) | 评论 (0)编辑 收藏

2010年10月20日 #

Get the whole arrangement of a string.
I got no better method to get this kind of sorting sequence.
Here is a simple implementation of printing whole arrangement.
Better one is expected now...
 2 #include <assert.h>
 3 #define N 10 /* do not set a big number for n! */
 5 /**
 6  * str target string.
 7  * oka sorted content.
 8  */
 9 void pnn(char* str, char* oka)
10 {
11     /* check str */
12     assert(str != NULL && strlen(str) <= N && strlen(str) >= 1);
13     if (strlen(str) == 1) {
14         printf("%s%c\n", oka, *str);
15         return;
16     }
17     /* i to record which char need to be sort now */
18     int i = 0;
19     while(1) {
20         /* define new container for input str to swap char */
21         char ipt[N];
22         memcpy(ipt, str, strlen(str)+1);
23         /* define new container for output str to add char */
24         char opt[N];
25         memcpy(opt, oka, strlen(oka)+1);
26         /* get position of char to be sort now */
27         char* ptr = ipt + i++;
28         if(*ptr == '\0'break;
29         /* swap char with the first one in ipt */
30         if(ptr != ipt) {
31             *ptr ^= *ipt;
32             *ipt ^= *ptr;
33             *ptr ^= *ipt;
34         }
35         /* add char into opt as the last one and set '\0' to end the opt */
36         opt[strlen(oka)] = *ipt;
37         opt[strlen(oka)+1= '\0';
38         /* recursively sort next char */
39         pnn(ipt+1, opt);
40     }
41 }
43 void permutation(char* str)
44 {
45     char aim[N];
46     memcpy(aim, str, strlen(str)+1);
47     char oka[1= {'\0'};
48     pnn(aim, oka);
49 }
51 int main(int argc, _TCHAR* argv[])
52 {
53     permutation("1234567");
54     getchar();
55     return 0;
56 }

posted @ 2010-10-20 16:48 JonsenElizee 阅读(256) | 评论 (0)编辑 收藏

1 int string2long(char* str, long* rtv)
2 {
3     for(int i = strlen(str), j = *rtv = 0*str >= '0' && *str <= '9'; i--, str++){
4         *rtv += (long)((*str - '0')*(pow(10, i-1)));
5     }
6     return *str == '\0' ? 1 : 0;
7 }
Please pay attention to j = *rtv = 0;
if there is no "j = ", *rtv will be redefined as int *rtv after ", " and address of rtv will be 0xcccccc.
So, inorder to set value of rtv in if sentence, just use a non-usage variable j.

to invoke the function in this way:

long rtv;
if(string2long("321", &rtv)) printf("rtv = %ld\n", rtv);
else puts("failure");

posted @ 2010-10-20 14:29 JonsenElizee 阅读(301) | 评论 (0)编辑 收藏

How to avoiding duplicated computing of recursive function like this one:
func(n) = func(n-1) + func(n-2) + func(n-3) and func(1) == func(2) == 1 and func(3) == 2.
or function like this: fabonaci:
fabonaci(n) = fabonaci(n-1) + fabonaci(n-2).

 1 int fabo(int n, int* ptr)
 2 {
 3     printf("fabo(%d)\n", n);
 4     if(n < 3
 5     {
 6         *ptr = 1;
 7         return 1;
 8     }
 9     else {
10         int tmp;
11         *ptr = fabo(n - 1&tmp);
13         return *ptr + tmp;
14     }
15 }
16 int fabonaci(int n)
17 {
18     int tmp;
19     return fabo(n, &tmp);
20 }
22 int xxx(int n)
23 {
24     printf("xxx(%d)\n", n);
25     if(n < 3)return 1;
26     else return xxx(n-1)+xxx(n-2);
27 }
28 int main()
29 {
30     int n = fabonaci(10);
31     printf("n = %d\n", n);
33     n = xxx(10);
34     printf("n = %d\n", n);
35     getchar();
36     return 0;
37 }

 1 /************************************************************************/
 2 /* func(n) = func(n-1) + func(n-2) + func(n-3)                          */
 3 /* func(1) = 1; func(2) = 1; func(3) = 2;                               */
 4 /************************************************************************/
 5 int funk(int n, int* n_1, int* n_2)
 6 {
 7     printf("funk(%d)\n", n);
 8     if(n == 3){
 9         *n_1 = 1;
10         *n_2 = 1;
11         return 2;
12     }
13     else{
14         int n_1_1, n_1_2;
15         *n_1 = funk(n-1&n_1_1, &n_1_2);
16         *n_2 = n_1_1;
17         return *n_1 + *n_2 + n_1_2;
18     }
19 }
20 int func(int n)
21 {
22     int n_1, n_2;
23     return funk(n, &n_1, &n_2);
24 }
25 int main()
26 {
27     int n = func(10);
28     printf("n = %d\n", n);
29     getchar();
30     return 0;
31 }

posted @ 2010-10-20 11:48 JonsenElizee 阅读(1164) | 评论 (0)编辑 收藏

2010年10月16日 #

     摘要: Post order accesing the binary tree with a flag to recording what kind of node is accessed.flag == 0 means made left move or accessed a left node.flag == 1 means made right move or accessed a right no...  阅读全文
posted @ 2010-10-16 14:18 JonsenElizee 阅读(408) | 评论 (0)编辑 收藏

2010年10月15日 #

int    atoi(const char *nptr); 
double atof(const char *nptr); 
long   atol(const char *nptr); 

long int strtol(const char *nptr,char **endptr,int base);
long int strtoul(const char *nptr,char **endptr,int base);
double strtod(const char *nptr,char **endptr);
char  *strchr(const char *s,char c); /* find first position of c in s */
int sscanf( const char *, const char *, ); /* read data from string matching format */
int  scanf( const char *, ); 
int fprintf( FILE *stream, const char *format,  );
int sprintf( char *buffer, const char *format [, argument]  );



* fopen(const char* filepath, const char* mode); //mode: "r": read; "w": write, create if not exist; "a": append, create if not exist;

int fread (void* buf, size_t size, size_t nitems, FILE* stream); // read nitems chars or to the EOF. so it could read multi-lines.
int fwrite(void* buf, size_t size, size_t nitems, FILE* stream); // write nitems chars or to the '\0' of buf.

char* fgets(char *buf, int nitems, FILE* stream);                // read at most one line with '\n'(holds it) or terminated by EOF.
int   fputs(char *buf, FILE* stream);                            // write strlen(buf) chars into stream and return real written char number.

int getc(FILE* stream);         // read next char and return EOF on end of file or error. 
int putc(int c, FILE* stream);  // return c on success, else EOF(-1).

int fgetc(FILE* stream);        // read next char and return EOF on end of file or error. 
int fputc(int c, FILE* stream); // return c on success, else EOF(-1).

int fflush(FILE *stream);       // return 0 on success, else EOF(-1).
int feof(FILE *stream);         // return 1 if reach EOF, else 0.
int fclose(FILE *stream);       // return 0 on success, else EOF(-1).

* freopen(char* filename, char* type, FILE* stream); // redirect stream to filename file
int fgetpos(FILE *stream,*fpos_t filepos); // get current file pointer position.
int fscanf(FILE *stream, char *format,[argument]);
int fseek(FILE *stream, long offset, int fromwhere); // SEEK_SET, SEEK_CUR, SEEK_END. 

void setbuf(FILE *steam, char *buf); 
int setvbuf(FILE *stream, char *buf, int type, unsigned size); // call it just after opening file.
long ftell(FILE *stream); // get current file pointer position.

int close(int fd);
int fcntl(int fd , int cmd);                        // #include <fcntl.h> 
int fcntl(int fd,int cmd,long arg); 
int fcntl(int fd,int cmd,struct flock * lock); 
int ioctl(int fd, int cmd,[int *argdx, int argcx]); // #include <sys/ioctl.h> 
int read(int fd, void *buf, int nbyte); 
int write(int fd, void *buf, int nbyte);  
long lseek(int fd, long offset, int fromwhere);     // SEEK_SET, SEEK_CUR, SEEK_END. 

char* gets( char *buffer ); // from stdio, over at '\n' and EOF and set '\n' to '\0'.
int fgetchar(void);         // from stdio and return EOF when error occurs.
int getch(void);            // #include <conio.h>, no echoing.
int getchar(void);          // #define getchar() fgetc(stdin)
int getche(void);           // echo char from stdio and continue at '\n'.
int putchar(int ch);        // put char into stdout
int puts(char *string);     // put string into stdout.
int scanf(char *format[,argument,]);


#include <assert.h> 
/* read line_length chars into line from sourcefile
/* return number of chars really read, else -1 for error.

int read_line(char* line, int line_length, FILE* sourcefile)
    assert(sizeof(char) == 1);
int n = 0;
while (1)
char c = fgetc(sourcefile);
if(ferror(sourcefile)) return -1;
if(c == EOF || line_length-- == 0) break;
        *line++ = c;
return n;

FILE* open_file_demo(
const char* filepath, const char* options)
    FILE* fp = fopen(filepath, options);
if(fp == NULL)
        perror("fopen failure!");
return fp;

void write_file_demo()
char* filepath = "D:/xxx.txt";
char* options = "a";
    FILE* fp = open_file_demo(filepath, options);
    assert(fp != NULL);
char content[][16] = {"write ", "file ", "demo"};
int i = 0;
for(i = 0; i < 3; i++)
char* str = content[i];
//int siz = fwrite(str, 1, strlen(str), fp);
        //if(ferror(fp)) perror("fwrite failure!");

/* write strlen(str) chars into fp. */
int rtv = fputs(str, fp); /* rtv = 0 means success. */
if(rtv == EOF) perror("fputs failure!"); /* rtv = EOF(-1) means error. */
    fputs("\n", fp);
if(ferror(fp)) perror("fputs failure!");

if(fclose(fp) != 0) perror("fclose failure!");

void read_file_demo()
char* filepath = "D:/xxx.txt";
char* options = "r";
    FILE* fp = open_file_demo(filepath, options);
    assert(fp != NULL);
while (feof(fp) == 0)
char line[128] = {0};
/* make sure sizeof(line)-1 */
/* fread could read many lines at one time. */
/* it will read sizeof(line)-1 chars or to the EOF. */
// int siz = fread(line, 1, sizeof(line)-1, fp);

/* fgets just read a line or sizeof(line)-1 chars at one time. */
// char* rtv = fgets(line, sizeof(line)-1, fp);

int siz = read_line(line, sizeof(line)-1, fp);
if (ferror(fp))
            perror("fread failure!");

        printf("%s", line);

if(fclose(fp) != 0) perror("fclose failure!");

int main()
return 0;

posted @ 2010-10-15 16:34 JonsenElizee| 编辑 收藏

 1 int main(int argc, char* argv[])
 3     char* str[] = {"Welcome""to""Fortemedia""Nanjing"};
 4     char** ptr = str + 1;
 5     printf("ptr = %s\n"*ptr);
 6     puts("1------------------------------");
 8     str[0= (*ptr+++ 2;//*ptr 取str+1所指的指针,*ptr + 2 指向了“to”后面的'\0'。
 9     printf("ptr = %s\n"*ptr);
10     printf("str = [%s]\n", str[0]);//[]
11     puts("2------------------------------");
13     str[1= *(ptr + 1);
14     printf("ptr = %s\n"*ptr);
15     printf("str = [%s]\n", str[1]);//[Nangjing]
16     puts("3------------------------------");
18     str[2= ptr[1+ 3;
19     printf("ptr = %s\n"*ptr);
20     printf("str = [%s]\n", str[2]);//[jing]
21     puts("4------------------------------");
23     int x = (str[2- str[1]);printf("x = %d\n", x);
24     str[3= ptr[0+ x;
25     printf("str = [%s]\n", str[3]);//[g]
26     printf("ptr[0] = %s\n", ptr[0]);
27     puts("5------------------------------");
29     getchar();
30     return 0;
31 }

posted @ 2010-10-15 10:07 JonsenElizee| 编辑 收藏

2010年10月13日 #

Categories within Debugging

Projects within Debugging

  • ald

    - The Assembly Language Debugger is a tool for debugging executable programs at the assembly level.
  • Antiparser

    - a fuzz testing and fault injection API.
  • BASH Debugger

    - Patched BASH shell with extra debugging support
  • Benchmark-Timer

    - Times and becnhmarks portions of code
  • Bug-buddy

    - GNOME bug-reporting utility
  • BugPort

    - QA system for software development
  • BuildBot

    - Automates the compile/test cycle of software development
  • Check

    - Unit testing framework for C
  • checker

    - Finds memory errors at runtime
  • clisp

    - ANSI Common Lisp compiler, debugger, and interpreter

    - Free implementation of Common Lisp
  • Condenser

    - Findis and removes duplicate Java code
  • CrocoPat

    - Tool for relational querying
  • Crossroads Load Balancer

    - Load balance utility for TCP
  • CUT

    - Unit-testing framework for C, C++, and Objective-C
  • CxxTest

    - JUnit/CppUnit/xUnit-like framework for C++
  • dbg

    - C++ debugging utilities
  • DBG-Client

    - Client for the DBG debugger
  • DBG-Server

    - PHP debugger and profiler
  • Dbug

    - Macro-based debugging library
  • ddd

    - Graphical front end for command line debuggers
  • dejaGnu

    - Framework to test programs
  • diapergluforth

    - Testing tool for shared object libraries
  • dvbsnoop

    - Presents streamed (live) information in human readable form
  • Dynamic Probes

    - Debugger

    - extensible logging software
  • Electric Fence

    - Memory debugger
  • f2w helpdesk

    - Web-based helpdesk package
  • GCL

    - Compiler and interpreter for Common Lisp
  • Gdb

    - GNU Debugger
  • ggcov

    - GUI for reporting test coverage data
  • Gnu 8085 Simulator

    - A graphical 8085 simulator and assembler with a debugger.
  • GNU Visual Debugger

    - Graphical front end for debuggers
  • Greg

    - Software testing framework
  • GUSS

    - Hardware simulator for debugging
  • Javachecker

    - Performs static analysis for Java source file
  • jf-unittest

    - a C++ unit test framework
  • Jlint

    - Java debugger
  • kdbg

    - GUI for gdb
  • KMD

    - Multi-processor debugger
  • Kodos

    - Tool for working with regular expressions
  • Ksymoops

    - Kernel oops and error message decoder
  • linice

    - Source-level kernel debugger
  • log4php

    - Php port of log4j
  • memcheck

    - Memory debugging tool
  • MemCheck Deluxe

    - Memory usage tracker and leak finder
  • Memwatch

    - Memory leak and corruption detection tool
  • mpatrol

    - Diagnoses run-time errors
  • Nemiver

    - a standalone graphical debugger for the GNOME desktop.
  • OTRS

    - Ticket request and email management system
  • Perl Critic

    - Critiques Perl source code for best-practices
  • PMD

    - Java source code analyzer
  • Pngcheck

    - PNG integrity tester and dumper/debugger
  • Pounder

    - Tests Java GUIs
  • PuDB

    - A full-screen, console-based Python debugger.
  • pvswitch

    - Lets users use different program installations on one machine
  • PyChecker

    - Helps fix bugs in Python source code
  • PyLint

    - Pylint analyzes Python source code
  • QtUnit

    - Testing framework for C++
  • redet

    - Tool for constructing and executing regular expressions
  • Remote GUD

    - Lets you debug a program running on a remote host
  • RLog

    - Message logging facility for C++
  • rpmlint

    - RPM error checker
  • Scmbug

    - Combines any source code version control system with any bug-tracking system
  • Sedsed

    - Generates debug files in sed
  • Sipsak

    - Tests SIP devices and applications
  • Steel Bank Common Lisp

    - Development environment for Common Lisp
  • Strace

    - Debugging tool
  • Synopsis

    - multi-language source code introspection tool
  • TCLP

    - Type checker for Prolog dialects
  • UDS Collection

    - C++ development and debugging library
  • UPnP-Inspector

    - The Inspector is an UPnP Device and Service analyzer.
  • Valgrind

    - Memory debugger
  • Winpdb

    - Python debugger
  • xpvm

    - Graphical console and monitor for PVM
  • Z80-ASM

    - Compiler for the Z80 CPU assembler
posted @ 2010-10-13 23:45 JonsenElizee 阅读(979) | 评论 (0)编辑 收藏

2010年10月11日 #

Get the data number that is not a duplicated one in 0.25 billion data set. the data in this big data set is of type int. And the limitation is that
you can only use 600M memory at most. the time complexity should be O(n).

For the data type is int, so, the range of data is [0, 2^32).
Here is my idea.

/* using two 256M array to record the existing state is the best way. */
int duplicated(int all[], int size)
    bit st1[256M] 
= {0}, st2[256M] = {0};
int cnt = 0;
for(dat : all)// for each data in all-data set
if (dat < 2^31) {  
if(st1[dat] == 0) st1[dat] = 1;
else if(st2[dat] == 0) { st2[dat] = 1; cnt++; }

    reset st1 and st2;
for(dat : all)// for each data in all-data set
if (dat >= 2^31) {
-= 2^31;
if(st1[dat] == 0) st1[dat] = 1;
else if(st2[dat] == 0) { st2[dat] = 1; cnt++; }
return cnt;

/* the time complexity is not a constant, O(1), it's O(2 * size/2), it means O(n). */
/* space complexity is O(1), a constant size depending on your processing division.*/
/* if we need to process one billion data with type int, this algorithm can also */
/* work well. because the precondition: 0 <= all[i] < 2^32. */
/* Whitout real implementation and full test, if any bug, any reply will be */
/* appreciated. */

posted @ 2010-10-11 09:42 JonsenElizee 阅读(1638) | 评论 (0)编辑 收藏

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