add numerical recipes library

lib/nr/ansi/recipes/fixrts.c

@@ -0,0 +1,35 @@
+
+#include <math.h>
+#include "complex.h"
+#define NMAX 100
+#define ZERO Complex(0.0,0.0)
+#define ONE Complex(1.0,0.0)
+
+void fixrts(float d[], int m)
+{
+	void zroots(fcomplex a[], int m, fcomplex roots[], int polish);
+	int i,j,polish;
+	fcomplex a[NMAX],roots[NMAX];
+
+	a[m]=ONE;
+	for (j=m-1;j>=0;j--)
+		a[j]=Complex(-d[m-j],0.0);
+	polish=1;
+	zroots(a,m,roots,polish);
+	for (j=1;j<=m;j++)
+		if (Cabs(roots[j]) > 1.0)
+			roots[j]=Cdiv(ONE,Conjg(roots[j]));
+	a[0]=Csub(ZERO,roots[1]);
+	a[1]=ONE;
+	for (j=2;j<=m;j++) {
+		a[j]=ONE;
+		for (i=j;i>=2;i--)
+			a[i-1]=Csub(a[i-2],Cmul(roots[j],a[i-1]));
+		a[0]=Csub(ZERO,Cmul(roots[j],a[0]));
+	}
+	for (j=0;j<=m-1;j++)
+		d[m-j] = -a[j].r;
+}
+#undef NMAX
+#undef ZERO
+#undef ONE