need help with prime
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hi,
I was trying to implement the sieve of eroathoses (I know I spelt this wrong) and it works. But i was trying to find all prime under 2 million.
The .cmd for visual studio just corrupts if I try to find all prime under 2million. I am guessing It's because overflow or something but I don't know for sure.
can you give me some hints on how to fix my code so the program won't corrupt. here is the code:
thanks
I was trying to implement the sieve of eroathoses (I know I spelt this wrong) and it works. But i was trying to find all prime under 2 million.
The .cmd for visual studio just corrupts if I try to find all prime under 2million. I am guessing It's because overflow or something but I don't know for sure.
can you give me some hints on how to fix my code so the program won't corrupt. here is the code:
#include<iostream>
#include<fstream>
#include<cmath>
#include<iomanip>
using namespace std;
void sieve(__int64 arry[], __int64 upto) // finds prime num.
{
int next(0);
for(__int64 i=0; i < upto; i++)//populate the arry starting from the value 2.
arry[i] = i+2 ;
for(__int64 k=1; k < upto;k++)
{
if(arry[k] >=1)
{
next = arry[k];
for(int l = k+1 ; l <= upto ; l++)
if(arry[l] % next==0)
arry[l]=0;
}
}
for(__int64 i=0;i<=upto;i++) //cout<< arry[] if it has a number greater than 0
{
if(arry[i]>0)
cout<<arry[i]<<endl;
}
}
int main()
{
__int64 upto =200; //This works but 2 million does not.
__int64 arry[201]; //same problem as above.
sieve(arry,upto);
return 0;
}thanks
Last edited by firstPerson : Dec 29th, 2008 at 2:20 pm.
ur using 32 bit compiler rit...
see this...
see this...
__int64 arry[201]; // in 32 bit compiler will be int arry[201]; // maks array size = 65535 __int64 arry[2000000]; // ?????
Last edited by cikara21 : Dec 29th, 2008 at 2:43 pm.
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Originally Posted by cikara21 
what do u mean...ur using 32 bit compiler rit...
I mean that when i try to find the all prime numbers below 2 million,
the program corrupts, but if i try to find all prime number below say 2000, it works perfectly. Try the program to see what i mean.
I don't get why it does not work for a large number.
Static memory space is generally very limited, if you want to create large array sizes then you need to use dynamic memory. But be sure to delete the array afterwards
Chris
cpluplus Syntax (Toggle Plain Text)
cplusplus Syntax (Toggle Plain Text)
Chris
Last edited by Freaky_Chris : Dec 29th, 2008 at 2:59 pm.
Knowledge is power -- But experience is everything
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Originally Posted by Freaky_Chris
Static memory space is generally very limited, if you want to create large array sizes then you need to use dynamic memory.But be sure to delete the array afterwardscpluplus Syntax (Toggle Plain Text)
Chris
hmm. not sure what you mean. I know the basics about pointers but haven't learned what new is or does. Care to explain?
So it's like i'm telling the computer to make extra memory by saying
__int64 *array = new __int64[2000000];
Is it the 'new' that tells the computer to make extra room?
__int64 *array = new __int64[2000000];
Is it the 'new' that tells the computer to make extra room?
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