Questions tagged [bitwise]

Bitwise refers to a bitwise operation which operates on one or more bit patterns or binary numerals at the level of their individual bits.

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5
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1answer
576 views

Bitwise operation to get the weekday name

The function days_name receive a val (string) corresponding to weekdays in hexadecimal. ...
3
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2answers
1k views

Emulating __uint128_t

I developed a lot of code locally with __uint128_t only to find out that it is not available on the target platform. I am now trying to write my own struct that ...
8
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1answer
2k views

Hexadecimal to RGB conversion

I am trying to convert hex to rgb, and rgb to hex. My current code doesn't seem optimal, and there is an issue with 0's in the hexadecimal. What do you think about the overall quality of this code? ...
13
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2answers
17k views

Validating UTF-8 byte array

I'm writing a validator function that receives a byte[] and checks whether it represents a valid UTF-8 byte sequence, according to this table. Is my approach ...
4
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4answers
314 views

BitShift code compacting

I'm new to Java programming and am really enjoying it. I made a bitshift program, but I think it's too long. I expect the program to: Let users input the number and degree to be shifted Specify if ...
6
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1answer
2k views

Implementing Karatsuba Multiplication Algorithm in Python

I am trying to implement Karatsuba multiplication algorithm for binary (base 2) numbers. A requirement is that the intermediate / final results must also be in binary so as to assist in educative ...
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3answers
564 views

Finding the largest of a series of numbers being XORed

I'm working on solving a problem involving finding the largest of a series of numbers being XORed. This is the actual problem: Xorq has invented an encryption algorithm which uses bitwise XOR ...
8
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3answers
208 views

Check if bit is only set once in a vector of int

I have a vector of uint16_t and I want to check if there is a bit which is only set in one vector. I then get its position within the vector as well as from the ...
5
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1answer
2k views

Why are these functions slower than BigInteger's included methods?

I tried writing alternative functions to Java's BigInteger.add(BigInteger.ONE), BigInteger.add(BigInteger), and ...
3
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1answer
180 views

Finding the 'Minimum' AND of all the possible subsets of a set

The subset size should be greater than or equal to 2. How can I speed up this code? ...
23
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3answers
6k views

Converting an IP

I've written a DNS tool in Node and would like to know if there's a better and more efficient way of handling the conversion from an IP to a long. I'm not too good at bitwise just yet and would like ...
3
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2answers
469 views

Function for splitting an integer into smaller values

This is the function I've implemented in an answer to this question. I've tried to make this as simple and idiomatic as possible, using C++11. Could this still be improved in any way? ...
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2answers
153 views

Is there a more optimal way to approach some of these bitwise functions?

I completed some bit manipulation exercises out of a textbook recently and have grasped onto some of the core ideas behind manipulating bits firmly. My main concern with making this post is for ...
10
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3answers
985 views

Template for endianness-free code, data always packed as BIG-Endian

It's been a while since I've been properly grilled about my code. I had this Idea which should probably never make it into production code but still I couldn't find anything seriously wrong with it ...
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2answers
4k views

Implementations of rotate, shift, XOR, NOT and AND

I am going through the example of SHA256 over at Wikipedia and wanted to make sure I understood all the operations of the manipulation math before trying to actually attempt the implementation itself. ...
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2answers
198 views

Displaying data as binary in C with bitmasks

I wrote a program to display data in memory as binary and it worked. (It gave me immense sense of satisfaction and joy to see this work. I guess this happens to newbies who are just testing the waters)...
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4answers
2k views

Arithmetic or logical right shifts

Is this code correct? Is there any major improvement I can ad in terms of number of operations? ...
51
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8answers
34k views

Efficiently checking if a number is divisible by 3

I'm looking for code review, best practices and optimizations. ...
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2answers
2k views

Fastest / most efficient random bit indexing in Python

Using Python/Cython, I am trying to construct an efficient way to index boolean values. I have been trying to use the bitarray and/or bitstring packages to construct a fast, non memory intensive way ...
8
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1answer
563 views

Optimizing multiplication of two polynomials in GF(2^32)

I have the following method for multiplying two polynomials in GF(232): ...
9
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3answers
9k views

Integer square root in x86 assembly (NASM)

This program calculates the square root of an unsigned 32-bit number with some bit fiddling to get a very close approximation, then one iteration of the Babylonian method to get an exact value. I don'...
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3answers
1k views

Bit exchange operation

I have been working on a certain task these days and after several hours of torture, I have done it! However, I believe the code that I have "crafted" is quite difficult to be understood and to be ...
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2answers
7k views

Bit packing and unpacking

I needed a variadic function to pack and unpack bits into integer types. This is my first attempt: ...
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2answers
405 views

Decomposing bitfield with Haskell: is recursion the only way to do this?

Here's a program to take a bitfield like 7 and decompose it into the flags [1,2,4]. Ignore that the algorithm for doing this doesn't use bit shifting/is stupid. Problems: it seems like I have to have ...
5
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1answer
126 views

Eliminating repetitiveness in code to test hash functions

I usually take my school code as a playground to mess around with things. I was given a bunch of premade hash functions and had to test their output and find when they reach a specific lower range. ...
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5answers
4k views

Setting and getting bits in C

I am just starting to get my feet wet with C; and am rather enjoying myself in doing so. This is sort of a follow up to my last question here. I am posting this ordinate to hopefully getting some ...
4
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1answer
167 views

Efficiently counting '1' bits in the first n bits

I have two functions to count the number of set '1' bits in the first offset bits of either a 64 bit number, or a bitmap struct. After some profiling, particularly ...
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4answers
4k views

Boolean expression complexity and bitwise operators

Given this kind of code: ...
5
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2answers
3k views

Gaussian blur - convolution algorithm

My program uses graphics convolution, an algorithm that processes pixels to make them round, soft and blurred. This particular algorithm is well-known, but its slowing down the operation of the whole ...
25
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4answers
48k views

Counting number of 1's and 0's from integer with bitwise operation

Is there a better way of doing this? ...
3
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2answers
239 views

Function for reading bits

I've made this simple function for reading N bits from an unsigned char* (with a possible offset) and I'm willing to share it here, get a review, suggestions for ...
2
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2answers
570 views

Copy and bit-invert ints in an std::vector

I want a second copy of an std::vector in which all elements are inverted, e.g. 0x01 in the first vector should be ...
2
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1answer
173 views

Take all the bits in a number and shift them to the left end

I wrote this program which takes all the bits in a number and shifts them to the left end (for example: 01010110 --> 11110000). It's and exercise from a book. It works, but it seems to be very ...
5
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3answers
17k views

Split a long integer into eight 4-bit values

It's an exercise from a book. There is a given long integer that I should convert into 8 4-bit values. The exercise is not very clear for me, but I think I understood the task correctly. I googled ...
11
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1answer
462 views

10x10 bitmapped square with bits

This program prints out a 10x10 square and uses only bit operations. It works well, but I don't like that global array. Can you tell me if the code is proper or not? ...
5
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1answer
548 views

Playing with bits using Java

How can I optimize the following class? prepareSharing packs bits on left and prepareMask counts the required bits for encoding ...
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1answer
1k views

Missing element from array (D&C) - code design/aesthetic improvement

I am trying to implement in C/C++ a 'classical' Divide and Conquer algorithm which solves the following problem "Given an array of n-1 numbers (int) from 0 to n, find the missing number". I am using ...
0
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1answer
209 views

Bitwise Logic optimization

I should be able to figure this out on my own, but I can't seem to wrap my head around how to optimize this set of logic for interpreting the existence of URL parameters. ...
2
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2answers
212 views

Color fading function [closed]

I found this old color fading function in my snippets folder and would like to implement it to one of my projects. It can be used to fade one color to another. It's a very long one-liner: ...
5
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2answers
3k views

Speed up a program to find the minimum Hamming distance

I have a solution to the puzzle at https://kattis.csc.kth.se/problem?id=codes. What can I do to make my algorithm much much faster? What the algorithm does is take an N×K matrix and search for the ...
3
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5answers
8k views

Divide group of numbers into two groups of which the sums are equal

I have a piece of code that divides a group of numbers into two groups of numbers of which the sums are equal. I created this because of a Stack Overflow question: For example: {10,15,20,5} will ...
2
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1answer
1k views

JavaScript xor function

I made simple JavaScript xor function. It accepts string, numeric array and mixed array (char, string, num) as params. It returns string or an array. Returning an array is a must!. All numbers are ...
2
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1answer
360 views

Simplify bit flags checking code

Please help make this code more cleaner. It's a part of window procedure that notifies my renderer before client area of window resized. I need to check two combinations of bit blags: some of them ...
4
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1answer
4k views

Bitwise Flag code for Python

I am looking for feedback on this compact Python API for defining bitwise flags and setting/manipulating them. Under the hood, FlagType extends int and all ...
0
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2answers
2k views

Spotify's “Reversed Binary Numbers” Problem [closed]

I wrote some Java code for Spotify's Reversed Binary Numbers puzzle and I tested it on my machine and I am almost positive that it behaves as expected. However, when I send it to puzzle AT spotify.com ...
14
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4answers
2k views

Exhaustive search for encryption keys

This does the job, but is not especially elegant. What is the preferred Pythonic idiom to my childish nests? ...
5
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1answer
9k views

16 bit checksum calculation [closed]

I need to calculate checksum using 16-bit ones' complement addition: ...
4
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1answer
805 views

Connect Four: Bitboard checking algorithm

I'm rather new to Clojure and so I decided to program a Connect Four for fun and learning. The code below is a Clojure implementation of this bitboard algorithm. The whole code can be found here: ...
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3answers
153 views

Multiplying many times

I needed to find away to left shift a number on a platform with buggy << and >> bitwise operators. I came up with a ...
5
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3answers
10k views

Base-36 encoding of a byte array

After posting a question about Alphanumeric Hash generation on StackOverflow, the most helpful answer was to change the conversion method from pulling 5-bit chunks of a binary hash value, to instead ...