The tag has no wiki summary.

learn more… | top users | synonyms

0
votes
0answers
11 views

How to find number of similar elements in two rows of two matrices? [closed]

I am surrounded in a problem! I have two matrices and index of rows are input and i have to find number of similar elements in those two rows!.. Here is my code!... ...
2
votes
1answer
39 views

Power method to calculate eigenvectors

I've implemented a program for computing eigenvectors of some random, symmetric, $N$x$N$ matrix using the power method. I have found difficulty in calculating all $N$ eigenvectors consistently, ...
2
votes
1answer
26 views

Solving for the matrix $W$ in an equation involving $W \cdot W^{T}$

Having large matrices, $W$ (the unknown) and $M$ (known), is it possible to solve for $W$ in this equation $$W \cdot W^{T} = M,$$ where $M$ can have negative entries.
4
votes
1answer
92 views

Which computational model is used to analyse the runtime of matrix multiplication algorithms?

Although I have already learned something about the asymptotic runtimes of matrix multiplication algorithms (Strassen's algorithm and similar things), I have never found any explicit and satisfactory ...
0
votes
1answer
42 views

Updating maximum sum subrectangle in a sparse matrix when one element is changed

I have an m x n matrix which is sparse with N non-zero entries. A modified version of Kadane's 2-d algorithm can find the maximum sum subrectangle in O(m N log n) time, which beats traditional ...
-1
votes
1answer
32 views

How to determine the address of an element in a square matrix given the base address? [closed]

I was asked this question in examination. A square matrix $M$ of size $10 \times 10$ is stored in memory with each element requiring 4 bytes of storage. If the base address at $M[0][0]$ is $1840$, ...
4
votes
1answer
39 views

A canonical representative, for this equivalence relation on matrices

This question is inspired by Constructing inequivalent binary matrices. Define the equivalence relation $\sim$ as follows: If $M,N$ are two $8\times 8$ binary matrices (all elements are $0$ or $1$), ...
3
votes
3answers
201 views

Number of submatrices with a particular sum

Given a $n\times n$ matrix A[0...n-1][0....n-1] where all entries are non-negative integers, and a non-negative integer K, I ...
2
votes
1answer
99 views

Which algorithms are usable for heatmaps and what are their pros and cons

This is a cross post from Stack Overflow, and DSP at Stackexchange since I cannot really decide which part of Stackexchange is most fitting. If this is the wrong place please tell me and I'll remove ...
5
votes
1answer
87 views

Undergrad resources for identifying regular languages with Myhill-Nerode matrices

I am taking an undergraduate CS Theory course and the material on finite automata and regular languages is being taught in a non-traditional manner. Instead of using regular expressions, the closure ...
3
votes
1answer
83 views

What are some applications of computing the permanent of a matrix?

What are some applications that require computing the permanent of a matrix? One application I know of is related to graph theory and matchings. Apparently, the number of perfect matchings of a ...
1
vote
1answer
94 views

Count elements of a sorted matrix that fall into a given interval

I have a $n\times n$ matrix called $M$, and two integers $k_\min$ and $k_\max$. Each row and each column of M is sorted in the increasing order. I would like to know if there is way I can count the ...
1
vote
0answers
30 views

Laplace's Approximation for graphical models

A question about Laplace's approximation: In Laplace's method, we need to find the mode of a function and take second order Taylor's expansion. The first order term will vanish (since the gradient is ...
1
vote
1answer
73 views

Significance of parameters in Tiny Mersenne Twister algorithm

I am trying to implement and optimize the Tiny Mersenne Twister (TinyMT) algorithm as required by an API I am developing with my team at work. The algorithm utilizes a C structure with 32-bit unsigned ...
0
votes
1answer
101 views

Number of permutation cycles in matrix transposition

I am trying to solve a problem on Sphere Online Judge (SPOJ) link to which is: http://www.spoj.com/problems/TRANSP/ The matrix can be thought of as a permutation and its transposition as another ...
2
votes
1answer
115 views

How to enumerate combinations in parallel

I have $n\times k$ matrix with $k<n$ and I would like to find all its $n\choose k$ submatrices which are $k\times k$ matrices that are the concatenations of all possible $k$ rows. Actually I tried ...
3
votes
1answer
87 views

Complexity of transposing matrices represented as list of row or column vectors

Given [[1,4,7],[2,5,8],[3,6,9]] which is a list of the column vectors of matrix |1, 2, 3| |4, 5, 6| |7, 8, 9| is $ \Omega(n^2) $ a lower bound for transposing? ...
1
vote
1answer
256 views

How do convolution matrices work?

How do those matrices work? Do I need to multiple every single pixel? How about the upperleft, upperright, bottomleft and bottomleft pixels where there's no surrounding pixel? And does the matrix work ...
3
votes
1answer
638 views

Algorithm for generating heat maps

I am looking to generate a heat map from some data. I have a value and a location (longitude and latitude). I understand generating a colour from the value, however I'm not sure how I would go about ...
7
votes
1answer
165 views

2-D peak finding complexity (MIT OCW 6.006)

In a recitation video for MIT OCW 6.006 at 43:30, Given an $m \times n$ matrix $A$ with $m$ columns and $n$ rows, the 2-D peak finding algorithm, where a peak is any value greater than or equal to ...
2
votes
1answer
79 views

LU decomposition with pivoting

I have to solve system of linear algebraic equations $AX=B$, where $A$ is a two-dimensional matrix with all elements of main diagonal equal to zero. How to solve this problem? Iterational methods are ...
2
votes
1answer
73 views

How to correlate a matrix of values to get a coordinated point?

I got a n*m matrix updated in realtime (i.e. about every 10ms) with values between 0 and 1024, and I want to work out from that matrix a multitouch trackpad behaviour, which is: generate one or more ...
3
votes
1answer
161 views

How do you go about designing a vector processor architecture for the sum of matrix products?

The following equation is a matrix expression where $B_i$ and $C_i^T$ are $n\times n$ matrices and k is a positive integer: $$P = \sum_{i=1}^k B_i C_i^T $$ So $P = B_1 C_1^T + B_2 C_2^T + \cdots ...
2
votes
2answers
897 views

Dynamic Programming Solution for Optimal Matrix Chain Multiplication Order

I have been thinking about why the dynamic programming approach to finding the optimal matrix chain order is better than a brute force approach that finds the optimal order by exploring all nested ...
6
votes
1answer
172 views

What's a fast algorithm to decide whether there is an $A_G$ corresponding to a given $\chi_G(\lambda)$?

Given an adjacency matrix $A_G$ of an undirected graph $G$, it is easy and straightforward to compute the characteristic polynomial $\chi_G(\lambda)$. What about the other way around? The problem can ...
5
votes
2answers
445 views

Matrix powering in $O(\log n)$ time?

Is there an algorithm to raise a matrix to the $n$th power in $O(\log n)$ time? I have been searching online, but have been unsuccessful thus far.
1
vote
1answer
360 views

Using Funk SVD with SGD?

I work on a recommender system framework which is implemented with a variant on Funk SVD (See his explanation of his algorithm here). However the framework that we are trying to integrate doesn't ...
10
votes
1answer
244 views

Common idea in Karatsuba, Gauss and Strassen multiplication

The identities used in multiplication algorithms by Karatsuba (integers) Gauss (complex numbers) Strassen (matrices) seem very closely related. Is there a common abstract framework/generalization? ...
7
votes
1answer
228 views

Probabilistic test of matrix multiplication with one-sided error

Given three matrices $A, B,C \in \mathbb{Z}^{n \times n}$ we want to test whether $AB \neq C$. Assume that the arithmetic operations $+$ and $-$ take constant time when applied to numbers from ...
7
votes
1answer
131 views

Find minimum number 1's so the matrix consist of 1 connected region of 1's

Let $M$ be a $(0, 1)$ matrix. We say two entries are neighbors if they are adjacent horizontal or vertically, and both entries are $1$'s. One wants to find minimum number of $1$'s to add, so every $1$ ...