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#define _GNU_SOURCE
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <getopt.h>
#include <errno.h>
/* matrix dimension */
static size_t dim;
/* options */
static struct option long_opts[] = {
{ "dim", required_argument, NULL, 'd' },
{ "1", no_argument, NULL, '1' },
{ "2", no_argument, NULL, '2' },
{ NULL, 0, NULL, 0 },
};
static int visit_every_element_1(const int *matrix, size_t dim)
{
int sum = 0;
/* row by row */
for (int i = 0; i < dim; ++i) {
for (int j = 0; j < dim; ++j) {
sum += matrix[i * dim + j];
}
}
return sum;
}
static int visit_every_element_2(const int *matrix, size_t dim)
{
int sum = 0;
/* column by column */
for (int j = 0; j < dim; ++j) {
for (int i = 0; i < dim; ++i) {
sum += matrix[i * dim + j];
}
}
return sum;
}
static inline void print_usage_and_die(void)
{
fprintf(stderr, "usage: matrix [-1|-2] [-d <size>]\n");
exit(EXIT_FAILURE);
}
int main(int argc, char **argv)
{
int *matrix, sum;
char *end;
int c, choice = 1;
dim = 10000;
while ((c = getopt_long(argc, argv, "d:12", long_opts, NULL)) != -1) {
switch (c) {
case 'd':
dim = strtoull(optarg, &end, 10);
if (end == optarg || *end != '\0' || errno == ERANGE) {
fprintf(stderr, "given dim is not valid\n");
return EXIT_FAILURE;
}
break;
case '1':
choice = 1;
break;
case '2':
choice = 2;
break;
default:
print_usage_and_die();
}
}
matrix = (int *)calloc(dim * dim, sizeof(int));
if (!matrix) {
perror("malloc() failed");
return EXIT_FAILURE;
}
sum = choice == 1 ? visit_every_element_1(matrix, dim) :
visit_every_element_2(matrix, dim);
printf("Bogus result: %d\n", sum);
return EXIT_SUCCESS;
}
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