Program execution terminates in Code Blocks - c

Question

I have written a program to measure execution time of quick sort and am using Code Blocks to compile and run it. When I input random set of numbers my program runs well for any size of data. But when I try to input ascending/descending sorted set of numbers, my program terminates for large data set (>35000) saying program stopped working.
This same code runs well on linux. But on linux I am not able to measure time using QueryPerformanceCounter(). So I have to use Code Blocks on windows.
#include<stdio.h>
#include<windows.h>
double PCFreq = 0.0;
__int64 CounterStart = 0;
void StartCounter()
{
LARGE_INTEGER li;
if(!QueryPerformanceFrequency(&li))
printf("QueryPerformanceFrequency failed!\n");
PCFreq = (double)li.QuadPart;
QueryPerformanceCounter(&li);
CounterStart = li.QuadPart;
}
double GetCounter()
{
LARGE_INTEGER li;
QueryPerformanceCounter(&li);
return (double)(li.QuadPart-CounterStart)/PCFreq;
}
int part(int a[],int low,int high)
{
int pivot,i,j,temp;
pivot=low;
i=low+1;
j=high;
while(i<=j)
{
while(a[i]<=a[pivot])
i++;
while(a[j]>a[pivot])
j--;
if(i<j)
{
temp=a[i];
a[i]=a[j];
a[j]=temp;
}
}
temp=a[j];
a[j]=a[pivot];
a[pivot]=temp;
return j;
}
void QuickSort(int a[],int first,int last)
{
int q;
if(first<last)
{
q=part(a,first,last);
QuickSort(a,first,q-1);
QuickSort(a,q+1,last);
}
}
int main()
{
int n,a[100000],i;
printf("Enter the size of array:");
scanf("%d",&n);
for(i=0;i<n;i++)
//a[i]=rand()%100000; //average case (random data)
a[i]=i; //ascending sorted input
//a[i]=n-1-i; //descending sorted input
/*
printf("The UNsorted array is:\n");
for(i=0;i<n;i++)
printf("%d ",a[i]);
printf("\n\n");
*/
StartCounter();
QuickSort(a,0,n-1);
printf("Sorting time %lf micro seconds\n",GetCounter()*1000000.0);
/*
printf("\nThe sorted array is:\n");
for(i=0;i<n;i++)
printf("%d ",a[i]);
printf("\n");
*/
return 0;
}
I am getting following error

Answer 1

If I use clock(3) (sufficient resolution for a quick test) on Linux it works up to and including the fixed limit of 100000. To avoid that fixed limit I used malloc() to reserve the memory dynamically in the following sketch (doesn't make a difference in the outcome, I just wanted to put it on the heap instead of the stack)
#include <time.h>
#include <stdlib.h>
// ALL CHECKS OMMITTED!
int main()
{
int n,*a,i;
clock_t start, stop;
printf("Enter the size of array:");
scanf("%d",&n);
a = malloc(sizeof(int) * n);
for(i=0;i<n;i++)
//a[i]=rand()%100000; //average case (random data)
a[i]=i; //ascending sorted input
//a[i]=n-1-i; //descending sorted input
/*
printf("The UNsorted array is:\n");
for(i=0;i<n;i++)
printf("%d ",a[i]);
printf("\n\n");
*/
start = clock();
QuickSort(a,0,n-1);
stop = clock();
printf("Sorting time %f seconds\n", (double)(stop- start)/CLOCKS_PER_SEC);
/*
printf("\nThe sorted array is:\n");
for(i=0;i<n;i++)
printf("%d ",a[i]);
printf("\n");
*/
free(a);
return 0;
}
Ascending array entries: 11 seconds for 100,000 entries and for a million…a segfaulta at
QuickSort (a=0x7ffff7ee3010, first=174677, last=199999)
(repeatable)
I think the recursion is just a wee bit too deep (stack size here: 8 megs which goes accord for 180,00 calls with two ints and a pointer and some overhead).
So: nothing actually wrong here.
EDIT
To show that it is indeed the stack lets increase it:
#include <time.h>
#include <stdlib.h>
#include <sys/resource.h>
// ALL CHECKS OMMITTED!
int main()
{
int n, *a, i;
clock_t start, stop;
// 256 MB
const rlim_t bigger_stack = 256L * 1024L * 1024L;
struct rlimit rlim;
int ret_set, ret_get;
ret_get = getrlimit(RLIMIT_STACK, &rlim);
fprintf(stderr, "get %d %d %d\n", ret_get, (int) rlim.rlim_max,
(int) bigger_stack);
if (ret_get == 0) {
if (rlim.rlim_cur < bigger_stack) {
rlim.rlim_cur = bigger_stack;
ret_set = setrlimit(RLIMIT_STACK, &rlim);
if (ret_set != 0) {
fprintf(stderr, "getrlimit %d, setrlimit %d\n", ret_get, ret_set);
}
}
}
printf("Enter the size of array:");
scanf("%d", &n);
a = malloc(sizeof(int) * n);
for (i = 0; i < n; i++)
//a[i]=rand()%100000; //average case (random data)
a[i] = i; //ascending sorted input
//a[i]=n-1-i; //descending sorted input
/*
* printf("The UNsorted array is:\n");
* for(i=0;i<n;i++)
* printf("%d ",a[i]);
* printf("\n\n");
*/
start = clock();
QuickSort(a, 0, n - 1);
stop = clock();
printf("Sorting time %f seconds\n", (double) (stop - start) / CLOCKS_PER_SEC);
/*
* printf("\nThe sorted array is:\n");
* for(i=0;i<n;i++)
* printf("%d ",a[i]);
* printf("\n");
*/
free(a);
return 0;
}
Checked with 200,000 elements: works in ca. 47 seconds.