31 lines
685 B
C
31 lines
685 B
C
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/* accès mémoire */
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#include<stdio.h>
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#include<time.h>
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#include <stdlib.h>
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#define N 8192
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int t[N][N];
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static inline double tstamp(void)
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{
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struct timespec tv;
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clock_gettime(CLOCK_REALTIME, &tv);
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return tv.tv_sec + tv.tv_nsec * 1.0e-9;
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}
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int main()
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{
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int i,j;
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double t1,t2;
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t1=tstamp();
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/* version 1 */ // for(i=0;i<N;i++) for(j=0;j<N;j++) t[i][j] = 1;
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/* version 2 */ for(i=0;i<N;i++) for(j=0;j<N;j++) t[j][i] = 1;
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t2=tstamp();
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printf("time = %lf\n",t2-t1);
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return 0;
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}
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// Le temps est différents entre les deux versions du programme, Pourquoi ?
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// Overload de cache, la mémoire parcours le tableau en ligne.
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// t[n][n]
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