bit

Support for Bit Vector Size Limit > 2^31 -1 in R?

由 痞子三分冷 提交于 2019-12-13 02:06:31
问题 I have been quite interested lately with extremely large vectors/arrays in R. I know from reading the documentation that the size limit of an array is 2 31 - 1 . However, using the CRAN package "bit", it is possible to instantiate a vector of booleans of length n while only using n/32 bits. I was wondering if it was possible to overcome R's internal limits by somehow implementing bit vectors (or some other way). It seems, to me, that it should be possible to have a bit vector with a limit of

手把手，嘴对嘴，讲解UCOSII嵌入式操作系统的任务调度策略（二）

由 匆匆过客 提交于 2019-12-12 23:35:59
继续...... if (ticks > 0u) { /* 延时参数是否为0 */ OS_ENTER_CRITICAL();　　　　　　　　　　　　/* 禁止中断 */ y = OSTCBCur->OSTCBY; OSRdyTbl[y] &= (OS_PRIO)~OSTCBCur->OSTCBBitX; if (OSRdyTbl[y] == 0u) { OSRdyGrp &= (OS_PRIO)~OSTCBCur->OSTCBBitY; } OSTCBCur->OSTCBDly = ticks; OS_EXIT_CRITICAL();　　　　　　　　　　 /* 开启中断 */ OS_Sched(); } 在上一段代码中，出现了一个陌生的数组： OSRdyTbl[]，跟踪这个变量可以找到它的定义，发现它仅仅是一个uint8型的数组，长度是8个。可以明确的告诉大家，这个数组很重要，应该算是任务优先级调度核心参数之一，与下面那个参数OSRdyGrp 合起来便可以作为任务就绪表。 ※接下来需要讲UCOSII系统的任务优先级调度策略，这一段有些复杂，需要反复思考，查阅大量的资料。 UCOSII的优先级策略 UCOSII操作系统最大可以管理64个任务（255个的暂时不讨论），每个任务都有唯一的优先级，从0开始到64，数字越小优先级越高，越优先进行系统调用，为了方面管理和调度

How does 1 left shift by 31 (1 << 31) work to get maximum int value? Here are my thoughts and some explanations I found online

由 大憨熊 提交于 2019-12-12 22:53:11
问题 I'm fairly new to bit manipulation and I'm trying to figure out how (1 << 31) - 1 works. First I know that 1 << 31 is 1000000000000000000000000000 and I know it's actually complement of minimum int value, but when I tried to figure out (1 << 31) - 1, I found an explanation states that, it's just 10000000000000000000000000000000 - 1 = 01111111111111111111111111111111 I was almost tempted to believe it since it's really straightforward. But is this what really happening? If it's not, why it

Password strength [closed]

由 旧时模样 提交于 2019-12-12 16:33:01
问题 Closed. This question is off-topic. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 8 years ago . Hey there, I wonder how to measure password strength best. I found two different pages: http://rumkin.com/tools/password/passchk.php and http://www.passwordmeter.com/ and they give completely different results about different passwords. Somehow it's obvious to measure in bit, but than it could be hard to tell

how many color combinations in a 24 bit image

由 本秂侑毒 提交于 2019-12-12 13:07:43
问题 I am reading a book and I am not sure if its a mistake or I am misunderstanding the quote. It reads... Nowadays every PC you can buy has hardware that can render images with at least 16.7 million individual colors. Rather than have an array with thousands of color entries, the images instead contain explicit color values for each pixel. A 24-bit display, of course, uses 24 bits, or 3 bytes per pixel, for color information. This gives 1 byte, or 256 distinct values each, for red, green, and

Generate bit vector with t random ones

由 六月ゝ 毕业季﹏ 提交于 2019-12-12 10:07:24
问题 I want to generate an array/vector v of size p with t ones and p-t zeros. The position of the t ones must be random. This is the solution that I've written so far, but I'm not sure if it's the most efficient one. In addition I never used random_device or mt19937 (found them here) before, so I don't know what are the possible drawbacks. #include <algorithm> #include <random> #include <vector> ... int p=10, t=3; std::vector<int> v(p,0); for(int i=0;i<t;i++) //better way? v[i] = 1; std::random

32bit cpu: how much memory can it use? [closed]

由 試著忘記壹切 提交于 2019-12-12 07:01:07
问题 Closed . This question needs to be more focused. It is not currently accepting answers. Want to improve this question? Update the question so it focuses on one problem only by editing this post. Closed 2 years ago . now i know this question has been asked quite a few times now but i'm not really wondering how much memory a 32bit processor can address neither theoretically nor practically. just a quick heads up, i come from a civil engineering background so i'm still learning in terms of

Writing 4 bits to a binary file with ofstream

由 雨燕双飞 提交于 2019-12-12 02:06:21
问题 If I have an unsigned integer between 0 - 16 and I want to write it to a binary file without writing a whole byte to it, how would one shift bits to achieve it? 0-16 means I only need 4 bits, so I should be able to store 2 different numbers in a single byte right? The following code writes 1 number to 1 byte: std::ofstream file; file.open("test.bin", std::ios::binary|std::ios::out); char oneByteNum = (char)fourByteNum; // Converting from some 4 byte integer to a 1 byte char file.write(

2019 SDN上机第7次作业

由 柔情痞子 提交于 2019-12-12 01:39:56
1.补充并运行basic代码 补充basic代码 /* -*- P4_16 -*- */ #include <core.p4> #include <v1model.p4> const bit<16> TYPE_IPV4 = 0x800; /************************************************************************* *********************** H E A D E R S *********************************** *************************************************************************/ typedef bit<9> egressSpec_t; typedef bit<48> macAddr_t; typedef bit<32> ip4Addr_t; header ethernet_t { macAddr_t dstAddr; macAddr_t srcAddr; bit<16> etherType; } header ipv4_t { bit<4> version; bit<4> ihl; bit<8> diffserv; bit<16> totalLen; bit<16>

2019 SDN上机第7次作业

由 邮差的信 提交于 2019-12-12 00:33:35
1.根据P4教程，将basic和basic_tunnel两个案例程序补充完整，成功运行。 任务是实现基础的交换机转发数据包功能 补充后代码如下： /* -*- P4_16 -*- */ #include <core.p4> #include <v1model.p4> const bit<16> TYPE_IPV4 = 0x800; /************************************************************************* *********************** H E A D E R S *********************************** *************************************************************************/ typedef bit<9> egressSpec_t; typedef bit<48> macAddr_t; typedef bit<32> ip4Addr_t; header ethernet_t { macAddr_t dstAddr; macAddr_t srcAddr; bit<16> etherType; } header ipv4_t { bit<4> version; bit<4> ihl; bit
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