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Questions tagged [matrix]

In mathematics, a matrix (plural matrices) is a rectangular array of numbers, symbols, or expressions, arranged in rows and columns. The individual items in a matrix are called its elements or entries.

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Computation of inter-grid distance array for 2D lattice

I have a 2D lattice with U × U number of grids. My goal is to create an array – of shape U^2 × U^2 – where each entry denotes the least-distance between each grid and any other grid. Currently, for ...
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Increase performance of a spate of 2x2 matrix multiplication

I would like to improve the performance of the piece of code below (in Fortran). It gives good results but the profiling tells me that it is where it spends most of its running time. Basically, it ...
2k views

4x4 Sudoku solver performance

The code is for a 4x4 Sudoku solver. It works fine when there are a small number of unfilled spaces (0's) but when I give the whole matrix input as 0's or so the solver takes a very long time. I need ...
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Performing a special multiplication on two square matrices

I have a function called mult2 that takes in two square NumPy matrices and returns a matrix that is the result of a special multiplication: ...
76 views

Find the number of pawns available for a rook to capture

I find that very very often with matrix questions, the traversal and comparison part of the solution is very verbose and repetitive. For example, this code (written for a coding challenge) to find ...
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4x4 matrix implementation in C++

I've been doing some 3D graphics in OpenGL lately and I needed a way to work with 4x4 matrices. My implementation supports the following operations: Matrix-matrix addition. Matrix-matrix subtraction. ...
700 views

If zero found in Matrix. make entire row & column zero

Problem is - If in an MxN matrix, a zero is encountered, the entire row and entire column should be set to zero. Example - 8 4 2 2 3 7 1 0 1 9 8 4 ...
677 views

Hardcoding matrix multiplication

I was doing a problem, SPOJ: FLIB. My code was running slow (getting Time Limit Exceeded error) when I was using Code1. However, my code accepted within the required time limit when I hardcoded the ...
2k views

Optimize Scipy Sparse Matrix Factorization code for SGD

I'm working on implementing the stochastic gradient descent algorithm for recommender systems (see Funk) using sparse matrices with Scipy. This is how a first basic implementation looks like: ...
170 views

Manipulating matrices for 3D drawing

I've written a short library for manipulating matrices for 3D drawing. I've tried to strike a balance between speed and readability. Anything to improve? ...
474 views

High performance exponential of a skew Hermitian matrix in Fortran 95

I'm new to Fortran, and this is pretty much my first escapade. Below is a function that I wrote which relies on calls to LAPACK. The function is sat in a module with some other functions and works ...
463 views

Back propagation neural network

This is the first time I tried to write a back propagation ANN and I would like to know what more experienced people think of it. The code is meant to distinguish if text is written in English, French ...
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Transpose of a very large matrix with fewer than 1021 rows with Python

I have a matrix of fewer than 1021 rows. I'd like to take its transpose, but it is too big for GNU datamash and awk solutions to ...
7k views

Matrix multiplication using functions in C

This exercise surprised me a little bit. I did not expect that gcc (GCC 6.3.0 in the MinGW suite) would use the C11 standard by default, which I realised after I ...
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Portable multithreaded matrix multiplication in C

I essentially took this progam, and made it compile and run on Windows too. Also, I incorporated some nice points made by Toby Speight. matrix.h ...
333 views

Multithread the variant of matrix multiplication

This is matrix multiplication. Big matrix split on the submatrix and multiplication in parallel, result matrices merge to result. How i can make this code better? ...