bitset

What is the performance of std::bitset?

由 …衆ロ難τιáo~ 提交于 2019-11-28 22:10:30
问题 I recently asked a question on Programmers regarding reasons to use manual bit manipulation of primitive types over std::bitset . From that discussion I have concluded that the main reason is its comparatively poorer performance, although I'm not aware of any measured basis for this opinion. So next question is: what is the performance hit, if any, likely to be incurred by using std::bitset over bit-manipulation of a primitive? The question is intentionally broad, because after looking online

in bitset, can i use “to_ulong” for a specific range of bits?

由 断了今生、忘了曾经 提交于 2019-11-28 12:01:12
hi im working on something that demands me to get access to specific/range of bits. i decided to use bitset because it is easy to get access to specific bits but can i extract a whole range of bits? Method A: return (the_bitset >> start_bit).to_ulong(); Method B (faster than method A by 100 times on my machine): unsigned long mask = 1; unsigned long result = 0; for (size_t i = start_bit; i < end_bit; ++ i) { if (the_bitset.test(i)) result |= mask; mask <<= 1; } return result; 来源： https://stackoverflow.com/questions/2177186/in-bitset-can-i-use-to-ulong-for-a-specific-range-of-bits

Bit vector and bitset

由 本秂侑毒 提交于 2019-11-28 11:36:12
问题 What is the difference between bit-vector and bitset container of stl ? Please explain. To my understanding bitset is the implementation of the concept of bitvector am I right or wrong? What are the other ways to implement bit vector? 回答1: bit_vector has the same interface as an std::vector , and is optimised for space. It not a part of standard C++. This documentation claims it is close to an STL vector<bool> , which presumably is quite close to a standard C++ std::vector<bool> . std::bitset

Why does std::bitset expose bits in little-endian fashion?

由 ∥☆過路亽．° 提交于 2019-11-28 01:57:12
When I use std::bitset<N>::bitset( unsigned long long ) this constructs a bitset and when I access it via the operator[] , the bits seems to be ordered in the little-endian fashion. Example: std::bitset<4> b(3ULL); std::cout << b[0] << b[1] << b[2] << b[3]; prints 1100 instead of 0011 i.e. the ending (or LSB) is at the little (lower) address, index 0. Looking up the standard, it says initializing the first M bit positions to the corresponding bit values in val Programmers naturally think of binary digits from LSB to MSB (right to left). So the first M bit positions is understandably LSB → MSB,

How does one store a vector<bool> or a bitset into a file, but bit-wise?

由 旧街凉风 提交于 2019-11-28 00:57:21
问题 How to write bitset data to a file? The first answer doesn't answer the question correctly, since it takes 8 times more space than it should. How would you do it ? I really need it to save a lot of true/false values. 回答1: Simplest approach : take consecutive 8 boolean values, represent them as a single byte, write that byte to your file. That would save lot of space. In the beginning of file, you can write the number of boolean values you want to write to the file; that number will help while

Python equivalent to Java's BitSet

由 风流意气都作罢 提交于 2019-11-27 22:59:55
问题 Is there a Python class or module that implements a structure that is similar to the BitSet? 回答1: There's nothing in the standard library. Try: http://pypi.python.org/pypi/bitarray 回答2: Have a look at this implementation in Python 3. The implementation basically makes use of the built-in int type, which is arbitrary precision integer type in Python 3 (where long is the Python 2 equivalent). #! /usr/bin/env python3 """ bitset.py Written by Geremy Condra Licensed under GPLv3 Released 3 May 2009

Convert Byte Array into Bitset

由 ▼魔方 西西 提交于 2019-11-27 22:30:05
I have a byte array generated by a random number generator. I want to put this into the STL bitset. Unfortunately, it looks like Bitset only supports the following constructors: A string of 1's and 0's like "10101011" An unsigned long. (my byte array will be longer) The only solution I can think of now is to read the byte array bit by bit and make a string of 1's and 0's. Does anyone have a more efficient solution? Something like this? (Not sure if template magic works here as I'd expect. I'm rusty in C++.) std::bitset bytesToBitset<int numBytes>(byte *data) { std::bitset<numBytes * CHAR_BIT>

convert bitset to int in c++

由 北慕城南 提交于 2019-11-27 14:50:42
问题 In c++. I initialize a bitset to -3 like: std::bitset<32> mybit(-3); Is there a grace way that convert mybit to -3 . Beacause bitset object only have methods like to_ulong and to_string . 回答1: Use to_ulong to convert it to unsigned long , then an ordinary cast to convert it to int . int mybit_int; mybit_int = (int)(mybit.to_ulong()); DEMO 来源： https://stackoverflow.com/questions/19583720/convert-bitset-to-int-in-c

Efficient way of iterating over true bits in std::bitset?

由 孤者浪人 提交于 2019-11-27 14:35:59
问题 Is there a way of iterating over a (possibly huge) std::bitset that is linear in the number of bits that are set to true ? I want to prevent having to check every single position in the bitset. The iteration should successively return the indices of each bit that is set to true. 回答1: A standard bitvector does not support efficient iteration over true bits - the runtime is always O(n), where n is the number of total bits, which has no dependence on k. However, there are specialized data

in bitset, can i use “to_ulong” for a specific range of bits?

由 佐手、 提交于 2019-11-27 06:41:02
问题 hi im working on something that demands me to get access to specific/range of bits. i decided to use bitset because it is easy to get access to specific bits but can i extract a whole range of bits? 回答1: Method A: return (the_bitset >> start_bit).to_ulong(); Method B (faster than method A by 100 times on my machine): unsigned long mask = 1; unsigned long result = 0; for (size_t i = start_bit; i < end_bit; ++ i) { if (the_bitset.test(i)) result |= mask; mask <<= 1; } return result; 来源： https:/
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