add numerical recipes library

2025-09-12 18:55:25 +09:00
parent d4dff245bd
commit 2c75620ec9
1344 changed files with 63869 additions and 0 deletions
--- a/lib/nr/cpp/recipes/twofft.cpp
+++ b/lib/nr/cpp/recipes/twofft.cpp
@@ -0,0 +1,32 @@
+#include "nr.h"
+
+void NR::twofft(Vec_I_DP &data1, Vec_I_DP &data2, Vec_O_DP &fft1,
+	Vec_O_DP &fft2)
+{
+	int nn3,nn2,jj,j;
+	DP rep,rem,aip,aim;
+
+	int n=data1.size();
+	nn3=1+(nn2=n+n);
+	for (j=0,jj=0;j<n;j++,jj+=2) {
+		fft1[jj]=data1[j];
+		fft1[jj+1]=data2[j];
+	}
+	four1(fft1,1);
+	fft2[0]=fft1[1];
+	fft1[1]=fft2[1]=0.0;
+	for (j=2;j<n+1;j+=2) {
+		rep=0.5*(fft1[j]+fft1[nn2-j]);
+		rem=0.5*(fft1[j]-fft1[nn2-j]);
+		aip=0.5*(fft1[j+1]+fft1[nn3-j]);
+		aim=0.5*(fft1[j+1]-fft1[nn3-j]);
+		fft1[j]=rep;
+		fft1[j+1]=aim;
+		fft1[nn2-j]=rep;
+		fft1[nn3-j]= -aim;
+		fft2[j]=aip;
+		fft2[j+1]= -rem;
+		fft2[nn2-j]=aip;
+		fft2[nn3-j]=rem;
+	}
+}