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#include<stdio.h>
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#include<stdlib.h>
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#include<math.h>
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#define N 10000
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double diff[N];
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double approx_log(double x, int T)
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{
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double s=0.0;
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int t;
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for (t=0; t < T; t++)
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s += pow(-1.0,t)*pow(x,t+1)/(t+1);
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return s;
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}
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double media(double *d)
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{
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int i;
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double s=0.0;
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for (i=0; i < N; i++)
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{
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s += d[i];
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}
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return s/N;
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}
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int main(void)
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{
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double x, m;
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int t, i, ret;
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FILE *f;
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srand48(0);
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f = fopen("logerr.dat", "w");
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if (f==NULL)
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{
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printf("[ERRORE] non riesco ad aprire il file diff.dat\n");
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exit(EXIT_FAILURE);
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}
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for (t=4; t < 100; t++)
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{
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for (i=0; i < N; i++)
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{
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do
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{
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x = 2.0*(drand48() - 0.5);
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}
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while (x==-1);
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diff[i] = fabs(approx_log(x, t) - log(1.0+x));
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}
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m=media(diff);
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ret=fprintf(f, "%d %.8f\n", t, m);
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if (ret < 0)
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{
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printf("[ERRORE] scrittura su disco fallita\n");
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exit(EXIT_FAILURE);
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}
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}
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fclose(f);
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}
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