25 lines
553 B
C++
25 lines
553 B
C++
#include "nr.h"
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void NR::cyclic(Vec_I_DP &a, Vec_I_DP &b, Vec_I_DP &c, const DP alpha,
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const DP beta, Vec_I_DP &r, Vec_O_DP &x)
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{
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int i;
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DP fact,gamma;
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int n=a.size();
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if (n <= 2) nrerror("n too small in cyclic");
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Vec_DP bb(n),u(n),z(n);
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gamma = -b[0];
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bb[0]=b[0]-gamma;
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bb[n-1]=b[n-1]-alpha*beta/gamma;
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for (i=1;i<n-1;i++) bb[i]=b[i];
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tridag(a,bb,c,r,x);
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u[0]=gamma;
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u[n-1]=alpha;
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for (i=1;i<n-1;i++) u[i]=0.0;
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tridag(a,bb,c,u,z);
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fact=(x[0]+beta*x[n-1]/gamma)/
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(1.0+z[0]+beta*z[n-1]/gamma);
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for (i=0;i<n;i++) x[i] -= fact*z[i];
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}
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