С++. What is faster and why?

Question

void test1(unsigned char **matrix) {
unsigned int start = clock();

int counter = 0;

for(int i = 0; i < N; i++) {
for(int j = 0; j < N; j++) {
if(matrix[i][j] >= 128) {
counter++;
}
}
}

unsigned int end = clock();
printf("%d\n", end-start);
}

void test2(unsigned char **matrix) {
unsigned int start = clock();

int counter = 0;

for(int j = 0; j < N; j++) {
for(int i = 0; i < N; i++) {
if(matrix[i][j] >= 128) {
counter++;
}
}
}

unsigned int end = clock();
printf("%d\n", end-start);
}

void test3(unsigned char **matrix) {
unsigned int start = clock();

int counter = 0;

for(int i = 0; i < N; i++) {
for(int j = 0; j < N; j++) {
counter+=matrix[i][j]>>7;
}
}

unsigned int end = clock();
printf("%d\n", end-start);
}

int main(int argc, char **argv) {

unsigned char **matrix = (unsigned char **)malloc(N * sizeof(unsigned char *));

for(int i = 0; i < N; i++) {
matrix[i] = (unsigned char *)malloc(N * sizeof(unsigned char *));
for(int j = 0; j < N; j++) {
matrix[i][j] = rand() % 255;
}
}

test1(matrix);
test2(matrix);
test3(matrix);

return 0;
}

Answer 1

Thank you for answer

Answer 2

please wrote comment to the code :)