handle large array size 1000000000

[lovelycse]

here it showing segmentation fault....how can i allocate 10^9 memory location

#include<cmath>
#include<stdlib.h>
#include<stdio.h>
//#define MAXSIZE 1000000000
int flag=0;
int flag1=0;
void prime(int n);
void pow2(int n);
int main()
{
long  long int n,k,g,sum=0,h;
//int MAXSIZE=100000000;
//long long int f[100000000];
 int *f;
f=( int*)malloc(sizeof(  int)*1000000000);
//printf("entre the no");
f[0]=0;
scanf("%lld",&n);
//k=n;
for(g=1;g<=n;g++)
{
k=g;
if(g==1 || g==2)
{
f[g]=1;
//printf("f[g]=%d\n",f[g]);
}
else{
pow2(g);
if(flag1==1){
//printf("pow\n");
f[g]=1;
}
else if(k%2==1)
f[g]=g;
else{
while(k%2!=1)
{
k=k/2;
}
f[g]=k;
}
//printf("f[g]=%d\n",f[g]);
}
}
for(h=1;h<=n;h++)
{
sum=sum+f[h];
}
printf("%lld\n",sum);
return(0);
}
/*void prime(int n)
{
int i,z;
for (i=2;i < n;i++)
{
if(n%i==0)
z=1;
}
if(z== 1)
flag=1;
//printf("not prime \n");
else
flag=0;
//printf("prime\n");
}*/
void  pow2(int n)
{
int d=0,p=0,m;
m=n;
while(n/2!=0)
{
n=n/2;
d++;
}


p=pow(2,d);

if(p==m)
flag1=1;
else
flag1=0;
}

[phantomotap]

O_o

That's about 4GiB.

If you want to allocate that much you'll need a 64-bit "OS" or a 32-bit "OS" with "PAE".

You also may need to configure the "OS" to let a single application own that much memory.

Beyond that, there are far better algorithms to deal with prime numbers.

Soma

[lovelycse]

its nt the code of prime number

O_o

That's about 4GiB.

If you want to allocate that much you'll need a 64-bit "OS" or a 32-bit "OS" with "PAE".

You also may need to configure the "OS" to let a single application own that much memory.

Beyond that, there are far better algorithms to deal with prime numbers.

Soma

[nonoob]

If you're lucky your system has 4 GB (4 x 10^9) bytes. I doubt any system can give you that many integers - since you're not the only one using the memory.
You need to rethink your requirements - perhaps consider arrays that are swapped to temporary files.

[qny]

Use a disk based approach.

1000000000 ints (32-bits ints) occupy almost 4G in memory.

Also, the header <cmath> is unrecognized by my compiler;
you don't need to cast the return value of malloc;
and use better indentation in the future.

[dmh2000]

as phantomap says, you need a 64 bit OS and compile for 64 bits. on windows 7 64, with Visual Studio 2012,

#include <stdio.h>
#include <stdlib.h>
int main()
{
	unsigned char *p;

	p = malloc(sizeof(int) * 1000000000);

	printf("%p\n",p);

    return 0;
}
outputs 000000013F730070

with a 32 bit build, it outputs 00000000.

and you don't necessarily need that much physical RAM, as the virtual memory system will swap pages as required. Although if you have TOO little RAM, it will thrash and run very slow.

[Salem]

> sum=sum+f[h];
If you put this inside the other loop, you wouldn't need to store a huge array at all.

Also, indentation is something you need to work on.