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foucault |
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//---------------------------------------------------------------------------
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#include <math.h>
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#include <stdio.h>
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#define EPS 3.0e-11
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#pragma hdrstop
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#include "gestionversion.h"
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#include "ot_quadrature_gauss.h"
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//---------------------------------------------------------------------------
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#pragma package(smart_init)
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void OT_QUADRATURE_GAUSS::gauss_legendre_points(double x1, double x2, double x[], double w[], int n)
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{
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int m,j,i;
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double z1,z,xm,xl,pp,p3,p2,p1;
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m=(n+1)/2;
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xm=0.5*(x2+x1);
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xl=0.5*(x2-x1);
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for (i=1;i<=m;i++) {
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z=cos(M_PI*(i-0.25)/(n+0.5));
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do {
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p1=1;
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p2=0;
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for (j=1;j<=n;j++) {
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p3=p2;
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p2=p1;
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p1=((2*j-1)*z*p2-(j-1)*p3)/j;
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}
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pp=n*(z*p1-p2)/(z*z-1);
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z1=z;
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z=z1-p1/pp;
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} while (fabs(z-z1) > EPS);
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x[i]=xm-xl*z;
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x[n+1-i]=xm+xl*z;
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w[i]=2*xl/((1-z*z)*pp*pp);
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w[n+1-i]=w[i];
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}
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} |
