Java Utililty Methods Matrix Multiply

List of utility methods to do Matrix Multiply

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Description

The list of methods to do Matrix Multiply are organized into topic(s).

Method

int[]multiplyMatrix(int[][] a, int[] b, int mod)
Multiplies the input matrix a with the input vector b % mod 
int m = b.length;
int[] resultMatrix = new int[m];
for (int i = 0; i < m; i++) {
    int total = 0;
    for (int j = 0; j < m; j++) {
        int aValue = a[i][j];
        int bValue = b[j];
        total += aValue * bValue;
...
double[][]multiplyMatrixByMatrix(double[][] a, double[][] b)
multiply Matrix By Matrix 
if (a[0].length != b.length) {
    throw new IllegalArgumentException("Cannot multiply a with b, columns of a != rows of b. ");
double[][] c = new double[a.length][b[0].length];
for (int i = 0; i < a.length; i++) {
    for (int x = 0; x < b.length; x++) {
        for (int y = 0; y < a[i].length; y++) {
            c[i][x] += (a[i][y] * b[y][x]);
...
double[][]multiplyMatrixes(double[][] m1, double[][] m2)
multiplies matrixes result = m1*m2 
double[][] result = new double[3][3];
multiplyMatrixes(m1, m2, result);
return result;
voidmultiplyQuad(final double[][] A, final double[][] B, final double[][] dest, int n)
Multiplies the quadratic matrix A (n-by-n) with the quadratic matrix B (n-by-n). 
assert hasShape(A, n, n);
assert hasShape(B, n, n);
assert hasShape(dest, n, n);
for (int i = 0; i < n; i++) {
    for (int j = 0; j < n; j++) {
        dest[i][j] = A[i][0] * B[0][j];
        for (int k = 1; k < n; k++) {
            dest[i][j] += A[i][k] * B[k][j];
...
float[][]multiplyScalars(float[][] x, float[][] y)
1d arrays can be different sizes within same parent array, but x and y must be same sizes in all ways. 
if (x.length != y.length)
    throw new Error("diff sizes");
float[][] ret = new float[x.length][];
for (int i = 0; i < x.length; i++) {
    int innerSize = x[i].length;
    ret[i] = new float[innerSize];
    if (innerSize != y[i].length)
        throw new Error("diff sizes");
...
float[][]multiplyScalars_optimizedByKnowingBothAreRectangle(float[][] x, float[][] y)
Not matrixMultiply. 
int b = x.length;
int c = x[0].length;
if (y.length != b || y[0].length != c)
    throw new Error("Diff sizes");
float[][] ret = new float[b][c];
for (int j = 0; j < b; j++) {
    for (int k = 0; k < c; k++) {
        ret[j][k] = x[j][k] * y[j][k];
...
voidmultiplySparse2dense(int[][][] as, int A, int[][][] bs, int B, int[][] c)
dense version of function above 
int[][] ax = as[0], aw = as[1], bx = bs[0], bw = bs[1];
int M = ax.length;
for (int m = 0; m < M; m++) {
    for (int i = 0; i < ax[m].length; i++) {
        int ii = ax[m][i];
        for (int j = 0; j < bx[m].length; j++) {
            int a = aw != null ? aw[m][i] : 1;
            int b = bw != null ? bw[m][j] : 1;
...
double[]multiplyVectorAndMatrix(double[] vector, double[][] matrix)
Multiplies a vector and a matrix. 
double[] res = new double[matrix.length];
for (int i = 0; i < matrix.length; i++) {
    for (int j = 0; j < vector.length; j++) {
        res[i] += matrix[i][j] * vector[j];
return res;
double[]multiplyVectorByMatrix(double[] v, double[][] m)
multiply vector by matrix 
double[] result = new double[3];
multiplyVectorByMatrix(v, m, result);
return result;