Hello,
Apparently I have a strange way of writing C. For example, here
is a short program showing how I use arrays in functions:
#include <stdio.h>
#include <stdlib.h>
void initialize(int mx, int meqn, double (*p_q)[meqn]);
int main(void) {
int mx = 20,i;
int meqn = 3;
int d1[20];
double q[mx][meqn];
double (*p_q)[meqn];
p_q=q;
initialize(mx, meqn, q);
for (i=0;i<mx;i++){
printf(" i %3d q[i][0] %15.7e\n",i, q[i][0]);
d1[i]=i;
}
return(0);
}
void initialize(int mx, int meqn, double (*p_q)[meqn]){
int i;
double *q;
q = (double *)p_q;
for (i=0;i<mx;i++){
p_q[i][0] = 1.*i;
p_q[i][1] = 2.*i;
p_q[i][2] = 3.*i;
}
}
I was told this was a terrible way to program with unnecessary
variables, etc. I was given the following example of how to clean up
my code and be more efficient in my programming and use dynamic memory
allocation to boot:
#include <stdio.h>
#include <stdlib.h>
void initialize(double p_q[][3], int , int );
int main(void) {
double **p_q;
int mx = 20,i;
int meqn = 3;
int d1[20];
p_q = malloc(sizeof(double)*mx*meqn);
initialize(p_q, mx, meqn);
for (i=0;i<mx;i++){
printf(" i %3d p_q[i][0] %15.7e\n",i, p_q[i][0]);
d1[i]=i;
}
return(0);
}
void initialize(double p_q[][3], int mx, int meqn){
int i;
for (i=0;i<mx;i++){
p_q[i][0] = 1.*i;
p_q[i][1] = 2.*i;
p_q[i][2] = 3.*i;
}
}
The problem is that while this second program compiles (with a
warning), it does not run. In fact, it gives a bus error.
So my question is 2-fold: what is wrong with the second program? and
what is the optimal way to write a program like this? Keep in mind
this is a simplified form of a much more sophisticated program
(several thousand lines of code). My thanks in advance.
--
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