Matrix Multiplikation - C

Question

Ich habe ein Programm erstellt, das Matrix Addition, Subtraktion und Multiplikation tut. Ich habe die Additions- und Subtraktionsabschnitte behandelt, aber als ich die Multiplikation erreichte, habe ich Probleme, die korrekten Werte auszugeben. Ich habe den Code nur mit der Multiplikationsfunktion unten platziert.

#define _CRT_SECURE_NO_WARNINGS 

#include <stdio.h> 
#include <stdlib.h> 

typedef struct { 

int *elements; 
int rows; 
int columns; 

} matrix; 

void main() { 

     matrix a, b, c; 

     void read_matrix(matrix *); 
     void deallocate(matrix *); 
     void print(matrix); 
     matrix add(matrix, matrix); 
     matrix subtract(matrix, matrix); 
     matrix multiply(matrix, matrix); 

     read_matrix(&a); 
     read_matrix(&b); 
     /* 
     c = add(a, b); 
     printf("The answer of Matrix (a + b) is \n\n"); 
     print(a); 
     printf("\n +\n\n"); 
     print(b); 
     printf("\n =\n\n"); 
     print(c); 
     printf("\n"); 

     deallocate(&c); 
     c = subtract(a, b); 
     printf("The answer of Matrix (a - b) is \n\n"); 
     print(a); 
     printf("\n -\n\n"); 
     print(b); 
     printf("\n =\n\n"); 
     print(c); 
     printf("\n"); 

     deallocate(&c); 
     */ 
     c = multiply(a, b); 
     printf("The answer of Matrix (a * b) is \n\n"); 
     print(a); 
     printf("\n *\n\n"); 
     print(b); 
     printf("\n =\n\n"); 
     print(c); 
     printf("\n"); 

} 

void read_matrix(matrix *z) { 

     int d1, d2, allc, i, x, y, j, val; 
     int res; 

     printf("\nWhat is the first dimension of the array? "); 
     res = scanf("%d", &d1); 

     if (res != 1) { 
      fprintf(stderr, "Something went wrong with your first dimension!"); 
        return; 
     } 

     printf("What is the second dimension of the array? "); 
     res = scanf("%d", &d2); 
     if (res != 1) { 
      fprintf(stderr, "Something went wrong with your second dimension!"); 
      return; 
     } 

     printf("Matrix Dimension is %dx%d\n", d1, d2); 

     allc = d1*d2; 

     (*z).elements = (int *)calloc(allc, sizeof(int)); 
     (*z).rows = d1; 
     (*z).columns = d2; 

     x = 0; 
     j = 0; 

     printf("\n"); 

     for (i = 0; i < d1; i++) { 

      x++; 

      for (y = 0; y < d2; y++) { 
       printf("Enter the value for row %d column %d: ", x, y + 1); 
       res = scanf("%d", &val); 
       if (res != 1) { 
        fprintf(stderr, "Something went wrong while reading value %d\n", x); 
        return; 
       } 

       (*z).elements[j++] = val; 
      } 

     } 
    } 

    void deallocate(matrix *c) { 

     free((*c).elements); 
     (*c).elements = NULL; 
     (*c).rows = 0; 
     (*c).columns = 0; 
    } 

    void print(matrix z) { 

     int i, j, x; 
     x = 0; 

     for (i = 0; i < z.rows; i++) { 

      printf("[ "); 

      for (j = 0; j < z.columns; j++) { 

       printf("%-4d", z.elements[x++]); 
      } 
      printf("]\n"); 
     } 
    } 

    matrix multiply(matrix a, matrix b) { 

     matrix c; 

     int a1, a2, b1, b2, allc, i, j, x, y, z, alc, addval, val; 

     i = 0; 
     j = 0; 
     alc = 0; 
     val = 0; 
     addval = 0; 

     a1 = a.rows; 
     a2 = a.columns; 
     b1 = b.rows; 
     b2 = b.columns; 

     allc = (a1 * b2); 

     c.elements = (int *)calloc(allc, sizeof(int)); 
     c.columns = a1; 
     c.rows = b2; 

     if (a2 != b1) { 
      printf("\n\nThe inner dimensions of your matrices do not match! Multiplication cannot be done!\n\n"); 
      exit(1); 
     } 


     for (x = 0; x < c.rows; x++) { 

      for (y = 0; y < c.rows; y++) { 

       for (z = 0; z < c.rows; z++) { 

        i = (i * c.rows); 

        addval = (a.elements[j]) * (b.elements[i]); 

        val += addval; 

        j++; 
        i++; 
       } 
       c.elements[alc] = val; 
       printf("VAL IS: %d\n\n", val); 

       val = 0; 

       i = 0; 
       alc++; 
      } 
     } 

     printf("\n\n"); 

     return c; 
    } 

In der Multiplikationsfunktion wird die dreifache verschachtelte for-Schleife soll durch oft genug gehen, die richtige Anzahl der Elemente für die Dimension des neuen Arrays zu drucken. Ich weiß, wie man Matrixmultiplikation macht, aber ich bin mir nicht sicher, ob ich es hier korrekt dargestellt habe.

Der Ausgang für ein Beispiel ist:

What is the first dimension of the array? 3 
What is the second dimension of the array? 3 
Matrix Dimension is 3x3 

Enter the value for row 1 column 1: 1 
Enter the value for row 1 column 2: 2 
Enter the value for row 1 column 3: 3 
Enter the value for row 2 column 1: 4 
Enter the value for row 2 column 2: 5 
Enter the value for row 2 column 3: 6 
Enter the value for row 3 column 1: 7 
Enter the value for row 3 column 2: 8 
Enter the value for row 3 column 3: 9 

What is the first dimension of the array? 3 
What is the second dimension of the array? 3 
Matrix Dimension is 3x3 

Enter the value for row 1 column 1: 1 
Enter the value for row 1 column 2: 2 
Enter the value for row 1 column 3: 3 
Enter the value for row 2 column 1: 4 
Enter the value for row 2 column 2: 5 
Enter the value for row 2 column 3: 6 
Enter the value for row 3 column 1: 7 
Enter the value for row 3 column 2: 8 
Enter the value for row 3 column 3: 9 


The answer of Matrix (a * b) is 

[ 1 2 3 ] 
[ 4 5 6 ] 
[ 7 8 9 ] 

    * 

[ 1 2 3 ] 
[ 4 5 6 ] 
[ 7 8 9 ] 

    = 

[ 216847534336951265054271] 
[ 1641572693-138635672036124672] 
[ 1352368309-50514195286739134] 

Press any key to continue . . . 

Answer 1

Im Folgenden meine Nacharbeiten des Codes ist die Matrixmultiplikation der Fall ist. Das Problem war mit Ihrer multiply() Funktion. Sie können sehen, dass es mit der a Matrix verloren geht, indem Sie nur die Variable j inkrementieren - in einer Arbeitslösung nimmt jedes Element der Matrix a mehrfach an der Multiplikation teil.

Ich änderte auch Ihre Routinen zu allen Pass-Zeigern zu Matrix-Strukturen, anstatt Ihre Mischung aus übergebenen Zeigern und Weitergabe/Rückgabe Matrixstrukturen direkt nach Wert. Ich denke, das ist konsistenter und einfacher zu folgen, aber es bedeutet, dass Sie Ihre anderen Matrix-Mathe-Routinen ändern müssen, um genauso zu arbeiten, wenn Sie es so halten.

#include <stdio.h> 
#include <stdlib.h> 

typedef struct { 
    int *elements; 
    int rows; 
    int columns; 
} matrix; 

void read_matrix(matrix *z) { 

    int d1, d2, val; 

    printf("\nWhat is the first dimension of the array? "); 
    int result = scanf("%d", &d1); 

    if (result != 1) { 
     fprintf(stderr, "Something went wrong with your first dimension!\n"); 
     exit(1); 
    } 

    printf("What is the second dimension of the array? "); 
    result = scanf("%d", &d2); 
    if (result != 1) { 
     fprintf(stderr, "Something went wrong with your second dimension!\n"); 
     exit(1); 
    } 

    printf("Matrix Dimension is %dx%d\n", d1, d2); 

    z->elements = calloc(d1 * d2, sizeof(int)); 
    z->rows = d1; 
    z->columns = d2; 

    int x = 0; 
    int j = 0; 

    printf("\n"); 

    for (int i = 0; i < d1; i++) { 

     x++; 

     for (int y = 0; y < d2; y++) { 
      printf("Enter the value for row %d column %d: ", x, y + 1); 
      result = scanf("%d", &val); 
      if (result != 1) { 
       fprintf(stderr, "Something went wrong while reading value (%d, %d)\n", x, y + 1); 
       exit(1); 
      } 

      z->elements[j++] = val; 
     } 
    } 
} 

void deallocate(matrix *c) { 

    free(c->elements); 

    c->elements = NULL; 
    c->rows = 0; 
    c->columns = 0; 
} 

void print(matrix *z) { 

    int x = 0; 

    for (int i = 0; i < z->rows; i++) { 

     printf("[ "); 

     for (int j = 0; j < z->columns; j++) { 

      printf("%-4d", z->elements[x++]); 
     } 

     printf("]\n"); 
    } 
} 

void multiply(matrix *a, matrix *b, matrix *c) { 

    if (a->columns != b->rows) { 
     fprintf(stderr, "The inner dimensions of your matrices do not match! Multiplication cannot be done!\n"); 
     exit(1); 
    } 

    c->elements = calloc(a->rows * b->columns, sizeof(int)); 
    c->columns = b->columns; 
    c->rows = a->rows; 

    int alc = 0; 

    for (int x = 0; x < a->rows; x++) { 

     for (int y = 0; y < b->columns; y++) { 

      int value = 0; 

      for (int z = 0; z < b->rows; z++) { 

       value += a->elements[z + x * a->columns] * b->elements[y + z * b->columns]; 
      } 

      c->elements[alc++] = value; 
     } 
    } 
} 

int main() { 

    matrix a, b, c; 

    read_matrix(&a); 
    read_matrix(&b); 

    multiply(&a, &b, &c); 

    printf("The answer of Matrix (a * b) is \n\n"); 
    print(&a); 
    printf("\n *\n\n"); 
    print(&b); 
    printf("\n =\n\n"); 
    print(&c); 
    printf("\n"); 

    deallocate(&a); 
    deallocate(&b); 
    deallocate(&c); 

    return 0; 
}