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//
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// Estimation of Pi using Monte Carlo exploration process
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// Cecill v2 Emmanuel QUEMENER <emmanuel.quemener@gmail.com>
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// gcc -O3 -o Pi_Simple Pi_Simple.c -lm
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//
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#include <math.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <omp.h>
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#include <limits.h>
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// Marsaglia RNG very simple implementation
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#define znew ((z=36969*(z&65535)+(z>>16))<<16)
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#define wnew ((w=18000*(w&65535)+(w>>16))&65535)
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#define MWC (znew+wnew)
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#define SHR3 (jsr=(jsr=(jsr=jsr^(jsr<<17))^(jsr>>13))^(jsr<<5))
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#define CONG (jcong=69069*jcong+1234567)
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#define KISS ((MWC^CONG)+SHR3)
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#define MWCfp MWC * 2.328306435454494e-10f
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#define KISSfp KISS * 2.328306435454494e-10f
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#define SHR3fp SHR3 * 2.328306435454494e-10f
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#define CONGfp CONG * 2.328306435454494e-10f
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#define ITERATIONS 1000000000
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#ifdef LONG
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#define LENGTH long long
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#else
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#define LENGTH int
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#endif
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LENGTH MainLoopGlobal(LENGTH iterations,unsigned int seed_w,unsigned int seed_z)
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{
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#if defined TCONG
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unsigned int jcong=seed_z;
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#elif defined TSHR3
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unsigned int jsr=seed_w;
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#elif defined TMWC
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unsigned int z=seed_z;
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unsigned int w=seed_w;
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#elif defined TKISS
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unsigned int jcong=seed_z;
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unsigned int jsr=seed_w;
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unsigned int z=seed_z;
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unsigned int w=seed_w;
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#endif
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LENGTH total=0,i;
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unsigned long inside;
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for (i=0;i<iterations;i++) {
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#if defined TINT32
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#define THEONE 1073741824
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#if defined TCONG
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unsigned int x=CONG>>17 ;
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unsigned int y=CONG>>17 ;
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#elif defined TSHR3
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unsigned int x=SHR3>>17 ;
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unsigned int y=SHR3>>17 ;
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#elif defined TMWC
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unsigned int x=MWC>>17 ;
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unsigned int y=MWC>>17 ;
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#elif defined TKISS
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unsigned int x=KISS>>17 ;
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unsigned int y=KISS>>17 ;
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#endif
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#elif defined TINT64
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#define THEONE 4611686018427387904
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#if defined TCONG
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unsigned long x=(unsigned long)(CONG>>1) ;
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unsigned long y=(unsigned long)(CONG>>1) ;
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#elif defined TSHR3
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unsigned long x=(unsigned long)(SHR3>>1) ;
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unsigned long y=(unsigned long)(SHR3>>1) ;
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#elif defined TMWC
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unsigned long x=(unsigned long)(MWC>>1) ;
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unsigned long y=(unsigned long)(MWC>>1) ;
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#elif defined TKISS
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unsigned long x=(unsigned long)(KISS>>1) ;
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unsigned long y=(unsigned long)(KISS>>1) ;
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#endif
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#elif defined TFP32
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#define THEONE 1.0f
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#if defined TCONG
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float x=CONGfp ;
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float y=CONGfp ;
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#elif defined TSHR3
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float x=SHR3fp ;
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float y=SHR3fp ;
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#elif defined TMWC
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float x=MWCfp ;
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float y=MWCfp ;
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#elif defined TKISS
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float x=KISSfp ;
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float y=KISSfp ;
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#endif
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#elif defined TFP64
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#define THEONE 1.0f
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#if defined TCONG
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double x=(double)CONGfp ;
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double y=(double)CONGfp ;
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#elif defined TSHR3
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double x=(double)SHR3fp ;
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double y=(double)SHR3fp ;
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#elif defined TMWC
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double x=(double)MWCfp ;
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double y=(double)MWCfp ;
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#elif defined TKISS
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double x=(double)KISSfp ;
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double y=(double)KISSfp ;
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#endif
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#endif
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inside=((x*x+y*y) < THEONE) ? 1:0;
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total+=inside;
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}
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return(total);
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}
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int main(int argc, char *argv[]) {
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unsigned int seed_w=1010,seed_z=2008;
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LENGTH iterations=ITERATIONS,inside=0;
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if (argc > 1) {
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iterations=(LENGTH)atoll(argv[1]);
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}
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else {
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printf("\n\tPi : Estimate Pi with Monte Carlo exploration\n\n");
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printf("\t\t#1 : number of iterations (default 1 billion)\n");
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}
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printf ("\n\tInformation about architecture:\n\n");
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printf ("\tSizeof int = %lld bytes.\n", (long long)sizeof(int));
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printf ("\tSizeof long = %lld bytes.\n", (long long)sizeof(long));
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printf ("\tSizeof long long = %lld bytes.\n\n", (long long)sizeof(long long));
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printf ("\tMax int = %u\n", INT_MAX);
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printf ("\tMax long = %ld\n", LONG_MAX);
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printf ("\tMax long long = %lld\n\n", LLONG_MAX);
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inside=MainLoopGlobal(iterations,seed_w,seed_z);
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float pi=4.*(float)inside/(float)iterations;
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printf("\tPi=%f with error %f and %lld iterations\n\n",pi,
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fabs(pi-4*atan(1))/pi,(long long)iterations);
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}
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