18 lines
313 B
C
18 lines
313 B
C
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void resid(res,u,rhs,n)
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double **res,**rhs,**u;
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int n;
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{
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int i,j;
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double h,h2i;
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h=1.0/(n-1);
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h2i=1.0/(h*h);
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for (j=2;j<n;j++)
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for (i=2;i<n;i++)
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res[i][j] = -h2i*(u[i+1][j]+u[i-1][j]+u[i][j+1]+u[i][j-1]-
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4.0*u[i][j])+rhs[i][j];
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for (i=1;i<=n;i++)
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res[i][1]=res[i][n]=res[1][i]=res[n][i]=0.0;
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}
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