Multiplication matricielle à l'aide de tableaux
J'essaie de créer une méthode de multiplication matricielle simple en utilisant des tableaux multidimensionnels ([2][2]). Je suis un peu nouveau à ce sujet, et je ne peux pas trouver ce que je fais mal. J'apprécierais vraiment toute aide pour me dire ce que c'est. Je préfère ne pas utiliser de bibliothèques ou quelque chose comme ça, je le fais surtout pour apprendre comment cela fonctionne. Je vous remercie beaucoup à l'avance.
Je déclare mes arays dans la méthode principale comme suit:
Double[][] A={{4.00,3.00},{2.00,1.00}};
Double[][] B={{-0.500,1.500},{1.000,-2.0000}};
A*B doit renvoyer la matrice d'identité. Il ne fait pas.
public static Double[][] multiplicar(Double[][] A, Double[][] B){
//the method runs and returns a matrix of the correct dimensions
//(I actually changed the .length function to a specific value to eliminate
//it as a possible issue), but not the correct values
Double[][] C= new Double[2][2];
int i,j;
////I fill the matrix with zeroes, if I don't do this it gives me an error
for(i=0;i<2;i++) {
for(j=0;j<2;j++){
C[i][j]=0.00000;
}
}
///this is where I'm supposed to perform the adding of every element in
//a row of A multiplied by the corresponding element in the
//corresponding column of B, for all columns in B and all rows in A
for(i=0;i<2;i++){
for(j=0;j<2;j++)
C[i][j]+=(A[i][j]*B[j][i]);
}
return C;
}
24
6 answers
, Vous pouvez essayer ce code:
public class MyMatrix {
Double[][] A = { { 4.00, 3.00 }, { 2.00, 1.00 } };
Double[][] B = { { -0.500, 1.500 }, { 1.000, -2.0000 } };
public static Double[][] multiplicar(Double[][] A, Double[][] B) {
int aRows = A.length;
int aColumns = A[0].length;
int bRows = B.length;
int bColumns = B[0].length;
if (aColumns != bRows) {
throw new IllegalArgumentException("A:Rows: " + aColumns + " did not match B:Columns " + bRows + ".");
}
Double[][] C = new Double[aRows][bColumns];
for (int i = 0; i < aRows; i++) {
for (int j = 0; j < bColumns; j++) {
C[i][j] = 0.00000;
}
}
for (int i = 0; i < aRows; i++) { // aRow
for (int j = 0; j < bColumns; j++) { // bColumn
for (int k = 0; k < aColumns; k++) { // aColumn
C[i][j] += A[i][k] * B[k][j];
}
}
}
return C;
}
public static void main(String[] args) {
MyMatrix matrix = new MyMatrix();
Double[][] result = multiplicar(matrix.A, matrix.B);
for (int i = 0; i < 2; i++) {
for (int j = 0; j < 2; j++)
System.out.print(result[i][j] + " ");
System.out.println();
}
}
}
26
Author: amatellanes, 2017-09-27 15:22:30
Java. Multiplication matricielle.
Testé avec des matrices de taille différente.
public class Matrix {
/**
* Matrix multiplication method.
* @param m1 Multiplicand
* @param m2 Multiplier
* @return Product
*/
public static double[][] multiplyByMatrix(double[][] m1, double[][] m2) {
int m1ColLength = m1[0].length; // m1 columns length
int m2RowLength = m2.length; // m2 rows length
if(m1ColLength != m2RowLength) return null; // matrix multiplication is not possible
int mRRowLength = m1.length; // m result rows length
int mRColLength = m2[0].length; // m result columns length
double[][] mResult = new double[mRRowLength][mRColLength];
for(int i = 0; i < mRRowLength; i++) { // rows from m1
for(int j = 0; j < mRColLength; j++) { // columns from m2
for(int k = 0; k < m1ColLength; k++) { // columns from m1
mResult[i][j] += m1[i][k] * m2[k][j];
}
}
}
return mResult;
}
public static String toString(double[][] m) {
String result = "";
for(int i = 0; i < m.length; i++) {
for(int j = 0; j < m[i].length; j++) {
result += String.format("%11.2f", m[i][j]);
}
result += "\n";
}
return result;
}
public static void main(String[] args) {
// #1
double[][] multiplicand = new double[][] {
{3, -1, 2},
{2, 0, 1},
{1, 2, 1}
};
double[][] multiplier = new double[][] {
{2, -1, 1},
{0, -2, 3},
{3, 0, 1}
};
System.out.println("#1\n" + toString(multiplyByMatrix(multiplicand, multiplier)));
// #2
multiplicand = new double[][] {
{1, 2, 0},
{-1, 3, 1},
{2, -2, 1}
};
multiplier = new double[][] {
{2},
{-1},
{1}
};
System.out.println("#2\n" + toString(multiplyByMatrix(multiplicand, multiplier)));
// #3
multiplicand = new double[][] {
{1, 2, -1},
{0, 1, 0}
};
multiplier = new double[][] {
{1, 1, 0, 0},
{0, 2, 1, 1},
{1, 1, 2, 2}
};
System.out.println("#3\n" + toString(multiplyByMatrix(multiplicand, multiplier)));
}
}
Sortie:
#1
12.00 -1.00 2.00
7.00 -2.00 3.00
5.00 -5.00 8.00
#2
0.00
-4.00
7.00
#3
0.00 4.00 0.00 0.00
0.00 2.00 1.00 1.00
10
Author: Dmytro Dzyubak, 2014-05-22 22:01:35
static int b[][]={{21,21},{22,22}};
static int a[][] ={{1,1},{2,2}};
public static void mul(){
int c[][] = new int[2][2];
for(int i=0;i<b.length;i++){
for(int j=0;j<b.length;j++){
c[i][j] =0;
}
}
for(int i=0;i<a.length;i++){
for(int j=0;j<b.length;j++){
for(int k=0;k<b.length;k++){
c[i][j]= c[i][j] +(a[i][k] * b[k][j]);
}
}
}
for(int i=0;i<c.length;i++){
for(int j=0;j<c.length;j++){
System.out.print(c[i][j]);
}
System.out.println("\n");
}
}
5
Author: Sivakumar Kuppusamy, 2013-07-12 22:12:08
Essayez ceci,
public static Double[][] multiplicar(Double A[][],Double B[][]){
Double[][] C= new Double[2][2];
int i,j,k;
for (i = 0; i < 2; i++) {
for (j = 0; j < 2; j++) {
C[i][j] = 0.00000;
}
}
for(i=0;i<2;i++){
for(j=0;j<2;j++){
for (k=0;k<2;k++){
C[i][j]+=(A[i][k]*B[k][j]);
}
}
}
return C;
}
2
Author: Dulanga, 2013-07-12 22:00:20
La méthode mults est une procédure (Pascal) ou un sous-programme(Fortran)
La méthode multMatrix est une fonction(Pascal,Fortran)
import java.util.*;
public class MatmultE
{
private static Scanner sc = new Scanner(System.in);
public static void main(String [] args)
{
double[][] A={{4.00,3.00},{2.00,1.00}};
double[][] B={{-0.500,1.500},{1.000,-2.0000}};
double[][] C=multMatrix(A,B);
printMatrix(A);
printMatrix(B);
printMatrix(C);
double a[][] = {{1, 2, -2, 0}, {-3, 4, 7, 2}, {6, 0, 3, 1}};
double b[][] = {{-1, 3}, {0, 9}, {1, -11}, {4, -5}};
double[][] c=multMatrix(a,b);
printMatrix(a);
printMatrix(b);
printMatrix(c);
double[][] a1 = readMatrix();
double[][] b1 = readMatrix();
double[][] c1 = new double[a1.length][b1[0].length];
mults(a1,b1,c1,a1.length,a1[0].length,b1.length,b1[0].length);
printMatrix(c1);
printMatrixE(c1);
}
public static double[][] readMatrix() {
int rows = sc.nextInt();
int cols = sc.nextInt();
double[][] result = new double[rows][cols];
for (int i = 0; i < rows; i++) {
for (int j = 0; j < cols; j++) {
result[i][j] = sc.nextDouble();
}
}
return result;
}
public static void printMatrix(double[][] mat) {
System.out.println("Matrix["+mat.length+"]["+mat[0].length+"]");
int rows = mat.length;
int columns = mat[0].length;
for (int i = 0; i < rows; i++) {
for (int j = 0; j < columns; j++) {
System.out.printf("%8.3f " , mat[i][j]);
}
System.out.println();
}
System.out.println();
}
public static void printMatrixE(double[][] mat) {
System.out.println("Matrix["+mat.length+"]["+mat[0].length+"]");
int rows = mat.length;
int columns = mat[0].length;
for (int i = 0; i < rows; i++) {
for (int j = 0; j < columns; j++) {
System.out.printf("%9.2e " , mat[i][j]);
}
System.out.println();
}
System.out.println();
}
public static double[][] multMatrix(double a[][], double b[][]){//a[m][n], b[n][p]
if(a.length == 0) return new double[0][0];
if(a[0].length != b.length) return null; //invalid dims
int n = a[0].length;
int m = a.length;
int p = b[0].length;
double ans[][] = new double[m][p];
for(int i = 0;i < m;i++){
for(int j = 0;j < p;j++){
ans[i][j]=0;
for(int k = 0;k < n;k++){
ans[i][j] += a[i][k] * b[k][j];
}
}
}
return ans;
}
public static void mults(double a[][], double b[][], double c[][], int r1,
int c1, int r2, int c2){
for(int i = 0;i < r1;i++){
for(int j = 0;j < c2;j++){
c[i][j]=0;
for(int k = 0;k < c1;k++){
c[i][j] += a[i][k] * b[k][j];
}
}
}
}
}
Où comme matrice d'entrée, vous pouvez entrer
InE.txt
4 4
1 1 1 1
2 4 8 16
3 9 27 81
4 16 64 256
4 3
4.0 -3.0 4.0
-13.0 19.0 -7.0
3.0 -2.0 7.0
-1.0 1.0 -1.0
Dans unix comme dgmm ligne exécuter la commande:
Java java MatmultE outE.txt
Et vous obtenez la sortie
OutC.txt
Matrix[2][2]
4.000 3.000
2.000 1.000
Matrix[2][2]
-0.500 1.500
1.000 -2.000
Matrix[2][2]
1.000 0.000
0.000 1.000
Matrix[3][4]
1.000 2.000 -2.000 0.000
-3.000 4.000 7.000 2.000
6.000 0.000 3.000 1.000
Matrix[4][2]
-1.000 3.000
0.000 9.000
1.000 -11.000
4.000 -5.000
Matrix[3][2]
-3.000 43.000
18.000 -60.000
1.000 -20.000
Matrix[4][3]
-7.000 15.000 3.000
-36.000 70.000 20.000
-105.000 189.000 57.000
-256.000 420.000 96.000
Matrix[4][3]
-7.00e+00 1.50e+01 3.00e+00
-3.60e+01 7.00e+01 2.00e+01
-1.05e+02 1.89e+02 5.70e+01
-2.56e+02 4.20e+02 9.60e+01
1
Author: Andrei, 2016-03-14 12:06:54
Essayez ceci, cela peut vous aider
import java.util.Scanner;
public class MulTwoArray {
public static void main(String[] args) {
int i, j, k;
int[][] a = new int[3][3];
int[][] b = new int[3][3];
int[][] c = new int[3][3];
Scanner sc = new Scanner(System.in);
System.out.println("Enter size of array a");
int rowa = sc.nextInt();
int cola = sc.nextInt();
System.out.println("Enter size of array b");
int rowb = sc.nextInt();
int colb = sc.nextInt();
//read and b
System.out.println("Enter elements of array a");
for (i = 0; i < rowa; ++i) {
for (j = 0; j < cola; ++j) {
a[i][j] = sc.nextInt();
}
System.out.println();
}
System.out.println("Enter elements of array b");
for (i = 0; i < rowb; ++i) {
for (j = 0; j < colb; ++j) {
b[i][j] = sc.nextInt();
}
System.out.println("\n");
}
//print a and b
System.out.println("the elements of array a");
for (i = 0; i < rowa; ++i) {
for (j = 0; j < cola; ++j) {
System.out.print(a[i][j]);
System.out.print("\t");
}
System.out.println("\n");
}
System.out.println("the elements of array b");
for (i = 0; i < rowb; ++i) {
for (j = 0; j < colb; ++j) {
System.out.print(b[i][j]);
System.out.print("\t");
}
System.out.println("\n");
}
//multiply a and b
for (i = 0; i < rowa; ++i) {
for (j = 0; j < colb; ++j) {
c[i][j] = 0;
for (k = 0; k < cola; ++k) {
c[i][j] += a[i][k] * b[k][j];
}
}
}
//print multi result
System.out.println("result of multiplication of array a and b is ");
for (i = 0; i < rowa; ++i) {
for (j = 0; j < colb; ++j) {
System.out.print(c[i][j]);
System.out.print("\t");
}
System.out.println("\n");
}
}
}
0
Author: Ragataj, 2015-08-28 14:03:28