90 lines
2.6 KiB
C
90 lines
2.6 KiB
C
/*
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* Program to factor big numbers using Brent-Pollard method.
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* See "An Improved Monte Carlo Factorization Algorithm"
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* by Richard Brent in BIT Vol. 20 1980 pp 176-184
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*/
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#include <stdio.h>
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#include "miracl.h"
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#define mr_min(a,b) ((a) < (b)? (a) : (b))
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int main()
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{ /* factoring program using Brents method */
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long k,r,i,m,iter;
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big x,y,z,n,q,ys,c3;
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miracl instance; /* create miracl workspace on the stack */
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#ifndef MR_STATIC
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miracl *mip=mirsys(&instance,16,0); /* initialise miracl workspace and define size of bigs here */
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char *mem=memalloc(mip,7); /* allocate space from the heap for 7 bigs */;
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#else
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miracl *mip=mirsys(&instance,MR_STATIC,0); /* size of bigs is fixed */
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char mem[MR_BIG_RESERVE(7)]; /* reserve space on the stack for 7 bigs */
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memset(mem,0,MR_BIG_RESERVE(7)); /* clear this memory */
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#endif
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x=mirvar_mem(mip,mem,0); /* initialise the 7 bigs */
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y=mirvar_mem(mip,mem,1);
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ys=mirvar_mem(mip,mem,2);
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z=mirvar_mem(mip,mem,3);
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n=mirvar_mem(mip,mem,4);
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q=mirvar_mem(mip,mem,5);
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c3=mirvar_mem(mip,mem,6);
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convert(mip,3,c3);
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printf("input number to be factored\n");
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cinnum(mip,n,stdin);
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if (isprime(mip,n))
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{
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printf("this number is prime!\n");
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return 0;
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}
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m=10L;
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r=1L;
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iter=0L;
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do
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{
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printf("iterations=%5ld",iter);
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convert(mip,1,q);
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do
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{
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copy(y,x);
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for (i=1L;i<=r;i++)
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mad(mip,y,y,c3,n,n,y);
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k=0;
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do
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{
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iter++;
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if (iter%10==0) printf("\b\b\b\b\b%5ld",iter);
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fflush(stdout);
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copy(y,ys);
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for (i=1L;i<=mr_min(m,r-k);i++)
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{
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mad(mip,y,y,c3,n,n,y);
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subtract(mip,y,x,z);
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mad(mip,z,q,q,n,n,q);
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}
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egcd(mip,q,n,z);
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k+=m;
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} while (k<r && size(z)==1);
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r*=2;
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} while (size(z)==1);
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if (mr_compare(z,n)==0) do
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{ /* back-track */
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mad(mip,ys,ys,c3,n,n,ys);
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subtract(mip,ys,x,z);
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} while (egcd(mip,z,n,z)==1);
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if (!isprime(mip,z))
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printf("\ncomposite factor ");
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else printf("\nprime factor ");
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cotnum(mip,z,stdout);
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if (mr_compare(z,n)==0) return 0;
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divide(mip,n,z,n);
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divide(mip,y,n,n);
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} while (!isprime(mip,n));
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printf("prime factor ");
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cotnum(mip,n,stdout);
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return 0;
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}
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