unsigned

C Unsigned int providing a negative value?

由 本小妞迷上赌 提交于 2019-11-26 07:49:54
问题 I have an unsigned integer but when i print it out using %d there is sometimes a negative value there? 回答1: Printing %d will read the integer as a signed decimal number, regardless of its defined type. To print unsigned numbers, use %u . This happens because of C's way to handle variable arguments. The compiler just pulls values from the stack (typed as void* and pointing to the call stack) and printf has to figure out what the data contains from the format string you give it to. This is why

海量数据处理-Topk引发的思考

由 霸气de小男生 提交于 2019-11-26 07:38:34
海量数据处理–TopK引发的思考 三问海量数据处理： 什么是海量数据处理，为什么出现这种需求？ 如何进行海量数据处理，常用的方法和技术有什么？ 如今分布式框架已经很成熟了，为什么还用学习海量数据处理的技术？ 什么是海量数据处理，为什么出现这种需求？ 如今互联网产生的数据量已经达到PB级别，如何在数据量不断增大的情况下，依然保证快速的检索或者更新数据，是我们面临的问题。所谓海量数据处理，是指基于海量数据的存储、处理和操作等。因为数据量太大无法在短时间迅速解决，或者不能一次性读入内存中。 从何解决我们上面提到的两个问题：时间问题和空间问题 时间角度，我们需要设计巧妙的算法配合合适的数据结构来解决；例如常用到的数据结构：哈希、位图、堆、数据库（B树），红黑树、倒排索引、Trie树等。空间角度：我们只需要分而治之即可，两大步操作：分治、合并。MapReduce就是基于这个原理。 如今分布式框架已经很成熟了，为什么还用学习海量数据处理的技术？ 这个问题，就相当于为什么要学习算法，因为大部分人在工作中都很少用到这些算法和高级的数据机构。武侠讲究内外兼修才是集大成着。算法就是内功，可以不用，不可以没有。算法更多的是理解和推到的过程，这就是为什么很多学数学和物理专业的学生，可以在计算机行业做的很好，因为他们的数学好，可以很好的理解各种推到过程和算法原理。最后一句话，知其然而后知其所以然

Unsigned Integer in Javascript

由 ▼魔方 西西 提交于 2019-11-26 06:33:46
问题 I\'m working on a page that processes IP address information, but it\'s choking on the fact that integers are signed. I am using bitwise operators to speed it up, but the 64th bit (signed/unsigned flag) is messing it up. Is there any way to force a number to be unsigned in Javascript? It seems to work fine, until subnet is greater than 30, or less than 2. Try this: <html> <body> <script type=\'text/javascript\'> document.write( (1 << 30) +\"<br/>\"); document.write( (1 << 31) +\"<br/>\");

Java equivalent of unsigned long long?

由 。_饼干妹妹 提交于 2019-11-26 06:17:31
问题 In C++, I enjoyed having access to a 64 bit unsigned integer, via unsigned long long int , or via uint64_t . Now, in Java longs are 64 bits, I know. However, they are signed. Is there an unsigned long (long) available as a Java primitive? How do I use it? 回答1: I don't believe so. Once you want to go bigger than a signed long, I think BigInteger is the only (out of the box) way to go. 回答2: Starting Java 8, there is support for unsigned long (unsigned 64 bits). The way you can use it is: Long

Why is a negative int greater than unsigned int? [duplicate]

由 荒凉一梦 提交于 2019-11-26 05:34:54
问题 This question already has an answer here: Comparison operation on unsigned and signed integers 7 answers int main(void) { unsigned int y = 10; int x = – 4; if (x > y) Printf(\"x is greater\"); else Printf(\"y is greater\"); getch(); return (0); } Output: x is greater I thought the output would be y is greater since it is unsigned. What\'s the reason behind this? 回答1: Because the int value is promoted to an unsigned int . specifically 0xFFFFFFFC on a 32-bit machine, which as an unsigned int is

bit shifting with unsigned long type produces wrong results

由 倾然丶 夕夏残阳落幕 提交于 2019-11-26 04:52:07
问题 I\'m a bit confused because I wanted to initialize a variable of type unsigned long whose size is 8 bytes on my system (on every modern system I suppose). When I want to assign 1 << 63 to the variable, I get a compiler warning however and the number is in fact 0. When I do 1 << 30 I get the expected result of 2 ^ 30 = 1073741824 . Yet when I do 1 << 31 , I get the result of 2 ^ 64 (I think; actually this shouldn\'t be possible) which prints 18446744071562067968 . Can anyone explain this

SQL SERVER数据页checksum校验算法

由 雨燕双飞 提交于 2019-11-26 04:11:47
在SQL SERVER2005以上版本中，数据页默认开启checksum，标识为m_flagBits & 0x200 == True，其值m_tornBits位于页头0x3C，4字节。 其算法概述如下： 读8KB 进BUF 将BUF头部 CHECKSUM的4字节值清0 uint32 checksum = 0 //初始checksum for i in range(0,15): //每扇区的初始checksum overall = 0; for ii in range(0,127): //对当前扇区的每个4字节做累加异或 overall = overall ^ BUF[i][ii]; //对每扇区的checksum进行移位，方法为向左移位15-i位， //左边移出的15-i位补到最低位。 checksum = checksum ^ rol(overall, 15- i); return checksum; //Gets checksum c源码如下： //***CODE***// #include <stdio.h> #include <stdlib.h> #define seed 15 //Initial seed(for first sector) #define CHAR_BIT 8 //***PROTOTYPES***// unsigned int page_checksum

Declaring an unsigned int in Java

由 China☆狼群 提交于 2019-11-26 03:49:25
问题 Is there a way to declare an unsigned int in Java? Or the question may be framed as this as well: What is the Java equivalent of unsigned? Just to tell you the context I was looking at Java\'s implementation of String.hashcode() . I wanted to test the possibility of collision if the integer were 32 unsigned int. 回答1: Java does not have a datatype for unsigned integers. You can define a long instead of an int if you need to store large values. You can also use a signed integer as if it were

Iteration over std::vector: unsigned vs signed index variable

由 本秂侑毒 提交于 2019-11-26 02:59:45
问题 What is the correct way of iterating over a vector in C++? Consider these two code fragments, this one works fine: for (unsigned i=0; i < polygon.size(); i++) { sum += polygon[i]; } and this one: for (int i=0; i < polygon.size(); i++) { sum += polygon[i]; } which generates warning: comparison between signed and unsigned integer expressions . I\'m new in the world of C++, so the unsigned variable looks a bit frightening to me and I know unsigned variables can be dangerous if not used correctly

Is unsigned integer subtraction defined behavior?

由 ￣綄美尐妖づ 提交于 2019-11-26 01:44:48
问题 I have come across code from someone who appears to believe there is a problem subtracting an unsigned integer from another integer of the same type when the result would be negative. So that code like this would be incorrect even if it happens to work on most architectures. unsigned int To, Tf; To = getcounter(); while (1) { Tf = getcounter(); if ((Tf-To) >= TIME_LIMIT) { break; } } This is the only vaguely relevant quote from the C standard I could find. A computation involving unsigned
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