Possible Solution

Content

Function Calls
Matrices and Vectors
Possible Solution
- Simple initialization and print functions for matrices
- - Test for row major
  - Test for col major

Make sure to verify that results (except for the memory layout) do not depend on the storage order.

Simple initialization and print functions for matrices

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

// function initGeMatrix
void
initGeMatrix(size_t m, size_t n,
             double *A,
             ptrdiff_t incRowA, ptrdiff_t incColA)
{
    for (size_t i=0; i<m; ++i) {
        for (size_t j=0; j<n; ++j) {
            A[i*incRowA + j*incColA] = i*n + j +1;
        }
    }
}

// function printGeMatrix
void
printGeMatrix(size_t m, size_t n,
              const double *A,
              ptrdiff_t incRowA, ptrdiff_t incColA)
{
    for (size_t i=0; i<m; ++i) {
        for (size_t j=0; j<n; ++j) {
            printf("%9.2lf ", A[i*incRowA + j*incColA]);
        }
        printf("\n");
    }
    printf("\n");
}

#ifndef COLMAJOR
#define COLMAJOR 1
#endif

int
main()
{
    printf("COLMAJOR = %d\n", COLMAJOR);

    size_t m = 5, n = 10;

    ptrdiff_t incRowA = COLMAJOR ? 1 : n;
    ptrdiff_t incColA = COLMAJOR ? m : 1;

    // allocate memory for A
    double *A = malloc(m*n*sizeof(double));
    if (!A) {
        abort();
    }

    // initialize matrix A
    initGeMatrix(m, n, A, incRowA, incColA);

    // print matrix A
    printf("A =\n");
    printGeMatrix(m, n, A, incRowA, incColA);

    // print how elements are stored in memory
    printf("memory layout of A:\n");
    printGeMatrix(1, m*n, A, 0, 1);

    // print a matrix view of A
    printf("A(0:2, 0:3) =\n");
    printGeMatrix(3, 4, A, incRowA, incColA);

    // print a matrix view of A
    printf("A(2:4, 3:8) =\n");
    printGeMatrix(3, 5, &A[2*incRowA+3*incColA], incRowA, incColA);

    // print a matrix view of A
    printf("A(2:4, 3:8)^T =\n");
    printGeMatrix(5, 3, &A[2*incRowA+3*incColA], incColA, incRowA);

    // release memory
    free(A);
}

Test for row major

thales$ gcc -Wall -std=c11 -DCOLMAJOR=0 -o matvec_01 matvec_01.c
thales$ ./matvec_01
COLMAJOR = 0
A =
     1.00      2.00      3.00      4.00      5.00      6.00      7.00      8.00      9.00     10.00 
    11.00     12.00     13.00     14.00     15.00     16.00     17.00     18.00     19.00     20.00 
    21.00     22.00     23.00     24.00     25.00     26.00     27.00     28.00     29.00     30.00 
    31.00     32.00     33.00     34.00     35.00     36.00     37.00     38.00     39.00     40.00 
    41.00     42.00     43.00     44.00     45.00     46.00     47.00     48.00     49.00     50.00 

memory layout of A:
     1.00      2.00      3.00      4.00      5.00      6.00      7.00      8.00      9.00     10.00     11.00     12.00     13.00     14.00     15.00     16.00     17.00     18.00     19.00     20.00     21.00     22.00     23.00     24.00     25.00     26.00     27.00     28.00     29.00     30.00     31.00     32.00     33.00     34.00     35.00     36.00     37.00     38.00     39.00     40.00     41.00     42.00     43.00     44.00     45.00     46.00     47.00     48.00     49.00     50.00 

A(0:2, 0:3) =
     1.00      2.00      3.00      4.00 
    11.00     12.00     13.00     14.00 
    21.00     22.00     23.00     24.00 

A(2:4, 3:8) =
    24.00     25.00     26.00     27.00     28.00 
    34.00     35.00     36.00     37.00     38.00 
    44.00     45.00     46.00     47.00     48.00 

A(2:4, 3:8)^T =
    24.00     34.00     44.00 
    25.00     35.00     45.00 
    26.00     36.00     46.00 
    27.00     37.00     47.00 
    28.00     38.00     48.00 
thales$

Test for col major

thales$ gcc -Wall -std=c11 -DCOLMAJOR=1 -o matvec_01 matvec_01.c
thales$ ./matvec_01
COLMAJOR = 1
A =
     1.00      2.00      3.00      4.00      5.00      6.00      7.00      8.00      9.00     10.00 
    11.00     12.00     13.00     14.00     15.00     16.00     17.00     18.00     19.00     20.00 
    21.00     22.00     23.00     24.00     25.00     26.00     27.00     28.00     29.00     30.00 
    31.00     32.00     33.00     34.00     35.00     36.00     37.00     38.00     39.00     40.00 
    41.00     42.00     43.00     44.00     45.00     46.00     47.00     48.00     49.00     50.00 

memory layout of A:
     1.00     11.00     21.00     31.00     41.00      2.00     12.00     22.00     32.00     42.00      3.00     13.00     23.00     33.00     43.00      4.00     14.00     24.00     34.00     44.00      5.00     15.00     25.00     35.00     45.00      6.00     16.00     26.00     36.00     46.00      7.00     17.00     27.00     37.00     47.00      8.00     18.00     28.00     38.00     48.00      9.00     19.00     29.00     39.00     49.00     10.00     20.00     30.00     40.00     50.00 

A(0:2, 0:3) =
     1.00      2.00      3.00      4.00 
    11.00     12.00     13.00     14.00 
    21.00     22.00     23.00     24.00 

A(2:4, 3:8) =
    24.00     25.00     26.00     27.00     28.00 
    34.00     35.00     36.00     37.00     38.00 
    44.00     45.00     46.00     47.00     48.00 

A(2:4, 3:8)^T =
    24.00     34.00     44.00 
    25.00     35.00     45.00 
    26.00     36.00     46.00 
    27.00     37.00     47.00 
    28.00     38.00     48.00 
thales$