Initialized pointer has all 0's instead of generated values [closed] - c

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I am implementing a sparse linear equation solver such as Lx = b. For this, I initialize a reference x vector named x_ref and generate an RHS vector b accordingly. However, both pointers seem empty somehow.
VALUE_TYPE is a macro and set to double
VALUE_TYPE *x_ref = (VALUE_TYPE *)malloc(sizeof(VALUE_TYPE) * n);
VALUE_TYPE *b = (VALUE_TYPE *)malloc(sizeof(VALUE_TYPE) * n);
for ( int i = 0; i < n; i++)
x_ref[i] = rand() % 10 + 1;
for (int i = 0; i < n; i++)
{
for (int j = cscColPtrTR[i]; j < cscColPtrTR[i+1]; j++)
{
int rowid = cscRowIdxTR[j]; //printf("rowid = %i\n", rowid);
b[rowid] += cscValTR[j] * x_ref[i];
}
}
After I print them as;
for(int i = 0; i < n; i++)
{
printf("%d\t\t%d\n", x_ref[i], b[i]);
}
The results are:
4226166 1977719296
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
I cannot understand what is wrong with it.

Answer 1

Rather use objects in the sizeof instead of types VALUE_TYPE *x_ref = (VALUE_TYPE *)malloc(sizeof(*x_ref) * n);
Use the correct printf formats. %d is used to output integers, not doubles.
#define VALUE_TYPE double
int main(void)
{
size_t n = 20;
VALUE_TYPE *x_ref = malloc(sizeof(*x_ref) * n);
VALUE_TYPE *b = malloc(sizeof(*b) * n);
for ( int i = 0; i < n; i++)
x_ref[i] = rand() % 10 + 1;
for ( int i = 0; i < n; i++)
printf("%d - %f\n", i, x_ref[i]);
}
https://godbolt.org/z/RKjZi8

Answer 2

First of all, you don't need to cast those mallocs, since it returns a void pointer, so the cast is implicit. I'm not sure why you are getting those zeros, but there are some remarks:
You need to seed the pseudo-random number generator:
#include <time.h>
#include <stdlib.h>
#include <stdio.h>
int main(void)
{
// Use current time as seed for random generator
srand(time(0));
for(int i = 0; i<4; i++)
printf(" %d ", rand());
return 0;
}
Initialize your b vector with a memset, because they are (as far as I can tell) accumulating values, so they should start from 0. As it is now, your vector may contain only gibberish.
I could not run your code because of the undefined references, but consider correcting those points :)