I am new to this, can someone help me with this, this is a C program optimizatio

Question

I am new to this, can someone help me with this, this is a C program optimization problem.

for (j=0; j //modify here

no matter what I do I am getting “checksum error” please see the entire code below

// sample run:

// $ gcc -Wall test.c -0 test
// $ time ./test


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

// Submitted code must have the correct values for these two constants:
// N_TIMES: 200000
// ARRAY_SIZE: 9973
// Feel free to play with these numbers below during test,
// but ensure you submit with the correct numbers.
//
#define N_TIMES 200000
#define ARRAY_SIZE 9973

int main (void)
{
int *array = calloc(ARRAY_SIZE, sizeof(int));
int sum = 0;
int checksum = 0;
int i;
int j;
int x;


printf("optimize performance ");

// Initialize the array with random values 0 to 13.
//
srand(time(NULL));
for (j=0; j < ARRAY_SIZE; j++) {

x = rand() / (int)(((unsigned)RAND_MAX + 1) / 14);
array[j] = x;
checksum += x;
}
//printf("Checksum is %d. ",checksum);

for (i = 0; i < N_TIMES; i++) {

// ---------------------------------------------------------------
// Do not alter anything above this line,
// Here is where you make your changes to
// optimize performance.

for (j=0; j // modify here

sum += array[j] + array[j+1] + array[j+2];
sum += array[j+3] + array[j+4] + array[j+5];
sum += array[j+6] + array[j+7] + array[j+8] + array[j+9];
}

// Do not alter anything below this line.
// ---------------------------------------------------------------

// Check each iteration.
//
if (sum != checksum) {
printf("Checksum error! ");
}
sum = 0;

}
return 0;
}

Explanation / Answer

#include <stdio.h>

#include <stdlib.h>

#include <time.h>

// Submitted code must have the correct values for these two constants:

// N_TIMES: 200000

// ARRAY_SIZE: 9973

// Feel free to play with these numbers below during test,

// but ensure you submit with the correct numbers.

#define N_TIMES 200000

#define ARRAY_SIZE 9973

int main (void)

{

int *array = (int *)calloc(ARRAY_SIZE, sizeof(int));

int sum = 0;

int checksum = 0;

int i;

int j;

int x;

printf("optimize performance ");

// Initialize the array with random values 0 to 13.

srand(time(NULL));

for (j=0; j < ARRAY_SIZE; j++) {

x = rand() / (int)(((unsigned)RAND_MAX + 1) / 14);

array[j] = x;

checksum += x;

}

printf("Checksum is %d. ",checksum);

for (i = 0; i < N_TIMES; i++) {

// ---------------------------------------------------------------

// Do not alter anything above this line,

// Here is where you make your changes to

// optimize performance.

for (j=0; j<ARRAY_SIZE; j=j+10) {

sum += array[j] + array[j+1] + array[j+2];

if(j<9970){

sum += array[j+3] + array[j+4] + array[j+5];

sum += array[j+6] + array[j+7] + array[j+8] + array[j+9];

}}

printf(" sum: %d and checksum: %d at loop: %d",sum,checksum,i+1);

// Do not alter anything below this line.

// ---------------------------------------------------------------

// Check each iteration.

if (sum != checksum) {

printf("Checksum error! ");

}

sum = 0;

}

return 0;

}

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