[Bug-gsl] [bug #51951] sparse add function gives wrong result (shorter than expected)

[Alfredo Correa]

Follow-up Comment #2, bug #51951 (project gsl):

Hi Patrick, sorry, for some reason the code posted removed the '*' symbols. (I
am also attaching the file this time)

This should compile with `gcc sparse.c -Wfatal-errors -lgsl -lgslcblas -lm`

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

#include <gsl/gsl_spmatrix.h>

int main(){

gsl_spmatrix* A = gsl_spmatrix_alloc(5, 4); /* triplet format */
gsl_spmatrix* B, *C, *D;
size_t i, j;

/* build the sparse matrix */
gsl_spmatrix_set(A, 0, 2, 3.1);
gsl_spmatrix_set(A, 0, 3, 4.6);
gsl_spmatrix_set(A, 1, 0, 1.0);
gsl_spmatrix_set(A, 1, 2, 7.2);
gsl_spmatrix_set(A, 3, 0, 2.1);
gsl_spmatrix_set(A, 3, 1, 2.9);
gsl_spmatrix_set(A, 3, 3, 8.5);
gsl_spmatrix_set(A, 4, 0, 4.1);

printf("printing all matrix elements:\n");
for (i = 0; i < 5; ++i)
for (j = 0; j < 4; ++j)
printf("A(%zu,%zu) = %g\n", i, j,
gsl_spmatrix_get(A, i, j));

/* print out elements in triplet format */
printf("matrix in triplet format (i,j,Aij):\n");
gsl_spmatrix_fprintf(stdout, A, "%.1f");

/* convert to compressed row format */
C = gsl_spmatrix_crs(A);
D = gsl_spmatrix_crs(A);

gsl_spmatrix_add(D, C, C);

printf("matrix in compressed row format:\n");
printf("i = [ ");
for (i = 0; i < C->nz; ++i)
printf("%zu, ", C->i[i]);
printf("]\n");

printf("p = [ ");
for (i = 0; i < C->size1 + 1; ++i)
printf("%zu, ", C->p[i]);
printf("]\n");

printf("d = [ ");
for (i = 0; i < C->nz; ++i)
printf("%g, ", C->data[i]);
printf("]\n");

printf("D matrix in compressed row format:\n");
printf("i = [ ");
for (i = 0; i < D->nz; ++i)
printf("%zu, ", D->i[i]);
printf("]\n");

printf("p = [ ");
for (i = 0; i < D->size1 + 1; ++i)
printf("%zu, ", D->p[i]);
printf("]\n");

printf("d = [ ");
for (i = 0; i < D->nz; ++i)
printf("%g, ", D->data[i]);
printf("]\n");

printf("end");
gsl_spmatrix_free(A);
gsl_spmatrix_free(B);
gsl_spmatrix_free(C);
gsl_spmatrix_free(D);
return 0;
}
```

(file #41753)
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Additional Item Attachment:

File name: sparse.c                       Size:1 KB


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