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add numerical recipes library

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yenru0
2025-09-12 18:55:25 +09:00
parent d4dff245bd
commit 2c75620ec9
1344 changed files with 63869 additions and 0 deletions
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24
lib/nr/cpp/recipes/cyclic.cpp Normal file
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#include "nr.h"
void NR::cyclic(Vec_I_DP &a, Vec_I_DP &b, Vec_I_DP &c, const DP alpha,
const DP beta, Vec_I_DP &r, Vec_O_DP &x)
{
int i;
DP fact,gamma;
int n=a.size();
if (n <= 2) nrerror("n too small in cyclic");
Vec_DP bb(n),u(n),z(n);
gamma = -b[0];
bb[0]=b[0]-gamma;
bb[n-1]=b[n-1]-alpha*beta/gamma;
for (i=1;i<n-1;i++) bb[i]=b[i];
tridag(a,bb,c,r,x);
u[0]=gamma;
u[n-1]=alpha;
for (i=1;i<n-1;i++) u[i]=0.0;
tridag(a,bb,c,u,z);
fact=(x[0]+beta*x[n-1]/gamma)/
(1.0+z[0]+beta*z[n-1]/gamma);
for (i=0;i<n;i++) x[i] -= fact*z[i];
}