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/rc.cpp
+++ b/lib/nr/cpp/recipes/rc.cpp
@@ -0,0 +1,32 @@
+#include <cmath>
+#include "nr.h"
+using namespace std;
+
+DP NR::rc(const DP x, const DP y)
+{
+	const DP ERRTOL=0.0012, TINY=1.69e-38, SQRTNY=1.3e-19, BIG=3.0e37;
+	const DP TNBG=TINY*BIG, COMP1=2.236/SQRTNY, COMP2=TNBG*TNBG/25.0;
+	const DP THIRD=1.0/3.0, C1=0.3, C2=1.0/7.0, C3=0.375, C4=9.0/22.0;
+	DP alamb,ave,s,w,xt,yt;
+
+	if (x < 0.0 || y == 0.0 || (x+fabs(y)) < TINY || (x+fabs(y)) > BIG ||
+		(y<-COMP1 && x > 0.0 && x < COMP2))
+			nrerror("invalid arguments in rc");
+	if (y > 0.0) {
+		xt=x;
+		yt=y;
+		w=1.0;
+	} else {
+		xt=x-y;
+		yt= -y;
+		w=sqrt(x)/sqrt(xt);
+	}
+	do {
+		alamb=2.0*sqrt(xt)*sqrt(yt)+yt;
+		xt=0.25*(xt+alamb);
+		yt=0.25*(yt+alamb);
+		ave=THIRD*(xt+yt+yt);
+		s=(yt-ave)/ave;
+	} while (fabs(s) > ERRTOL);
+	return w*(1.0+s*s*(C1+s*(C2+s*(C3+s*C4))))/sqrt(ave);
+}