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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33 views
Where is the bottleneck in my Cython code?
The profile tells me it took ~15s to run, but without telling me more.
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4
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0answers
47 views
Refactoring while-do array comparison function into tail recursion with F#
As part 2 of my other question concerning this long running project I've been inquiring about on CR, I reimplemented my generic function for determining if an array of arrays is a sub-array or ...
6
votes
3answers
204 views
Inner product of random floats written to file
My goals are to make this code:
faster
more idiomatic C++
What the code does:
take an integer command-line argument N
make a vector of ...
4
votes
5answers
188 views
Search algorithm for specific values in a 3D array/matrix being super slow
I'm trying to create code that reads a text file (containing (double) numbers between 0 and 1) and filling up a 3D array/matrix (calling it matrix from now on) with ...
9
votes
3answers
374 views
How many semi magic squares are there?
I want to write a program to work out how many semi-magic squares there are.
Here is the definition of semi-magic squares
If we define \$H_n(t)\$ is the number of semi magic squares which ...
6
votes
3answers
79 views
Searching all diagonals of a 2D M x M array
I've started writing a piece of code to help me search for an object in all the objects found in the diagonals of an M x M 2D array.
Though the code works, I'd like to know if there is a way I can ...
3
votes
1answer
41 views
Initializing an array of relative coordinates of all adjacent 2D matrix cells
The program should output this:
_1 _1
_1 0
_1 1
0 _1
0 1
1 _1
1 0
1 1
Currently I have this code:
...
11
votes
4answers
1k views
“Two-pass algorithm” implementation in Java
I'm rather new to Java and to algorithms in general. I implemented the so called Two-pass algorithm, and want to know if there are improvements to my way of implementing it. What it does is it takes a ...
6
votes
1answer
79 views
Linear algebra, reduced row echelon form - function 1
This is a derivative post from here.
This is just a general review, so the question is the same:
Is there something...
That you would consider as a bad practice and why?
That is just bad in some ...
5
votes
1answer
95 views
Linear algebra, reduced row echelon form
The code that I am sharing here for you to review today, is a segment of a JavaScript library that I am going to write as time goes by for fun. It is only the two functions in the following code:
...
1
vote
0answers
25 views
Avoiding boundaries if-cases when filtering image matrix
I have the following MATLAB Code which I want to optimize.
It's related to an image matrix (2D) which I want to filter.
Though it is MATLAB code, the same problem would arise in C code.
The problem ...
1
vote
0answers
32 views
Why does lu-factorization make my program slower?
I'm trying to calculate the smallest eigenvalue of the matrix A by using the "inverted exponentiation method" (see the code). I manage to find the smallest eigenvalue, but when I try to optimize the ...
3
votes
1answer
79 views
Point in a polygon algorithm
I am implementing a Point in polygon algorithm.
Inputs:
M, N: size of the matrix
poly: a ...
2
votes
1answer
58 views
How can I enhance my jigsaw puzzle solver function?
I'm working on writing code which gets several pieces of an image, and reconstructs them to one whole picture. The images are represented by matrices, and two pieces should be "glued" if the right ...
5
votes
1answer
113 views
Optimizing multiplication of square matrices for full CPU utilization
Cross-post from Stack Overflow since this is very code intensive
Problem
I am learning about HPC and code optimization. I attempt to replicate the results in Goto's seminal matrix multiplication ...
2
votes
1answer
42 views
Finding given element in minimum steps from matrix [closed]
A N*N size matrix is entered. The condition is that each element of the matrix is greater than the elements above it and left to it.
Or, it can be said that all the elements on the right side and ...
5
votes
2answers
160 views
Calculate fibonacci in O(log n)
This program calculates the \$n\$th fibonacci number, in \$O(\log n)\$ time. I'm looking for code review, optimizations, and best practices.
...
2
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1answer
29 views
3
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0answers
50 views
my arcBall rotation code
I am trying to visualize a pointcloud centered around the origin. I also want to have a user controlled rotation for which I found the arcball.
Below is my implementation. ...
4
votes
1answer
63 views
Optimization of matrix determinant calculation
I have this algorithm that calculates the matrix determinant using recursive divide-and conquer-approach:
...
2
votes
1answer
40 views
Less For, more MATLABesque?
I have written a piece of MATLAB code that (hopefully) calculates CECT. I have two matrices of psychophysiological measures - one for brain data, one for heart rate; both are of the format epochs * ...
10
votes
3answers
395 views
Find biggest basin
Problem Statement
A group of farmers has some elevation data, and we’re going to help
them understand how rainfall flows over their farmland.
We’ll represent the land as a ...
10
votes
2answers
441 views
Finding average of eight immediate neighbors of a matrix
I have this basic Java code to find average of eight immediate neighbors of a matrix.
Is there any way to simplify or merge any part of it, or can I refactor it?
I'm a beginner in Java programming ...
10
votes
1answer
569 views
3
votes
1answer
65 views
Sort 3x3 grid by rotating 2x2 subgrids
This question originates from this post.
Anyway, I'm trying to solve the following problem:
Given a 3x3 grid with numbers 1-9, for example:
2 8 3
1 4 5
7 9 6
I ...
3
votes
2answers
45 views
Implementing Transpose
I'm implementing transpose in Haskell.
-- transpose [[1,2,3],[4,5,6],[7,8,9]]
-- [[1,4,7],[2,5,8],[3,6,9]]
Please give it a ...
6
votes
2answers
60 views
Increment the neighbors of a cell in a matrix
Let's say you want to increment the cells around the position (x,y) in a square matrix m of size ...
4
votes
1answer
60 views
Matrix rotation efficiency
I am not sure if I should be using recursion or not or if it even helps in increasing the performance of my algorithm. I feel as though I am creating and replacing too many arrays by calling my inner ...
4
votes
1answer
60 views
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:
...
6
votes
1answer
57 views
Average of positive and negative part of numpy matrix
I’ve got a matrix of data and I want to take the average of the positive and negative parts of the values.
Is there a more Pythonic way of doing it?
...
6
votes
1answer
94 views
Calculating Euclidean norm for each vector in a sparse matrix
Below is a naive algorithm to find nearest neighbours for a point in some n-dimensional space.
...
4
votes
1answer
110 views
Optimize vector rotation
I have a trivial function that rotates 2d vectors, and a method in a class representing a polygon that rotates every point in the polygon around an origin. The code is fairly optimized as it is, but I ...
2
votes
1answer
117 views
Parsing MWNumericArray to C# code optimization
This is my function returning matrices from Matlab. This code run very slowly.
I was trying to use Parallel.For in-order to run it in parallel threads but I got ...
5
votes
1answer
134 views
Searching in a sorted 2D matrix
If I was at an interview, and wrote this code, what would you think? Please be brutal.
Time it took to wrote it: 13 minutes
Problem:
Write an efficient algorithm that searches for a value in an ...
7
votes
2answers
786 views
Repetitive For Loops in 2048 Game
I have the following function defined in a program that implements the 2048 game. I tried condensing the repeating part of the code into one loop containing +1 offset variables for the indices, which ...
13
votes
1answer
159 views
Finding a zero crossing in a matrix
I am trying create an algorithm for finding the zero crossing (check that the signs of all the entries around the entry of interest are not the same) in a two dimensional matrix, as part of ...
3
votes
1answer
112 views
Shift data in multidimensional array
I'm currently facing a problem where I have to shift data in a multidimensional JS array in different directions, but I think the first solution I whipped up is not as efficient as it could be (some ...
9
votes
1answer
86 views
Gauss-Seidal implementation
The code is an implementation of the Gauss–Seidel method. I would like a general review of the code.
PS: I use code::blocks IDE
...
2
votes
2answers
148 views
A matrix with square diagonals and transpose being increments of other
Construct a matrix with the following property:
North-west to South East diagonals are squares.
Matrix[i][j] + 1 = Matrix[j][i] for each i less than j.
Example of such m a matrix is ...
5
votes
1answer
87 views
In 8-puzzle finding nr of steps moving a tile to the right place
In 8-puzzle I want to count the number of moves it would take to move a specific tile to it's goal place. The problem is my method for this is >100 lines long which is obviously way too much. I'll ...
2
votes
1answer
624 views
Turning 1D array to 2D array in TicTacToe
To check a win in my TicTacToe game, I have created a 2D array that contains all the combination that a game can be won in, like so:
...
29
votes
0answers
408 views
Capture the notion of invertible functions
I find sometimes it is useful to capture the notion of invertible functions.
The idea is that if two functions f :: a -> b and ...
7
votes
2answers
236 views
Counting linear conflicts of the state of 8 puzzle for heuristic
I need to find linear conflicts of 8 puzzle state, state is represented by int[9], goal state is {1,2,3,4,5,6,7,8,0}. A linear conflict would be if in a line two ...
9
votes
2answers
310 views
C struct or pointer to struct?
I am currently using this code (and more) to deal with 2D matrices. I am not very proficient in C, so I am not quite sure, if this is a good way of doing it.
I've seen other people in similar ...
5
votes
3answers
81 views
More efficient (or correct) way to make image grouping work?
It might be easier to read the explanation of what I was trying to do, and implement it a completely different way, rather than go through the code. But the code does what I want it to do, just ...
11
votes
5answers
565 views
Set matrix zeros
I solved this problem in about 11 minutes (with all 50+ test cases passed).
I think most of you already know me by now, and I truly appreciate your advice, but please be brutal and judge me as if I ...
5
votes
2answers
294 views
Fixed size matrix implementation
I implemented a fixed-size matrix class which supports basic matrix operations (cannot use C++11). What do you think, and how could it be improved?
...
1
vote
2answers
193 views
Performance with C++ algorithm
This is an algorithm I'm trying to optimize. I was trying to use openMP without any success.
I know the code is long but most of it is params init.
Please try to explain why I need to change any ...
5
votes
1answer
57 views
Orchard Partitioning in to close-to-equal sectors
The task (from this site) is to create a program that will solve a problem where a matrix (size n * n), which contains integers, is to be divided into four parts, the sums of which are as close to ...
10
votes
3answers
460 views
Row/Column Transpose
I was wondering if there is a smarter way of doing the following code. Basically what is does is that it opens a data file with a lot of rows and columns. The columns are then sorted so each column is ...
