add numerical recipes library

lib/nr/ansi/recipes/rd.c

@@ -0,0 +1,59 @@
+
+#include <math.h>
+#define NRANSI
+#include "nrutil.h"
+#define ERRTOL 0.05
+#define TINY 1.0e-25
+#define BIG 4.5e21
+#define C1 (3.0/14.0)
+#define C2 (1.0/6.0)
+#define C3 (9.0/22.0)
+#define C4 (3.0/26.0)
+#define C5 (0.25*C3)
+#define C6 (1.5*C4)
+
+float rd(float x, float y, float z)
+{
+	float alamb,ave,delx,dely,delz,ea,eb,ec,ed,ee,fac,sqrtx,sqrty,
+		sqrtz,sum,xt,yt,zt;
+
+	if (FMIN(x,y) < 0.0 || FMIN(x+y,z) < TINY || FMAX(FMAX(x,y),z) > BIG)
+		nrerror("invalid arguments in rd");
+	xt=x;
+	yt=y;
+	zt=z;
+	sum=0.0;
+	fac=1.0;
+	do {
+		sqrtx=sqrt(xt);
+		sqrty=sqrt(yt);
+		sqrtz=sqrt(zt);
+		alamb=sqrtx*(sqrty+sqrtz)+sqrty*sqrtz;
+		sum += fac/(sqrtz*(zt+alamb));
+		fac=0.25*fac;
+		xt=0.25*(xt+alamb);
+		yt=0.25*(yt+alamb);
+		zt=0.25*(zt+alamb);
+		ave=0.2*(xt+yt+3.0*zt);
+		delx=(ave-xt)/ave;
+		dely=(ave-yt)/ave;
+		delz=(ave-zt)/ave;
+	} while (FMAX(FMAX(fabs(delx),fabs(dely)),fabs(delz)) > ERRTOL);
+	ea=delx*dely;
+	eb=delz*delz;
+	ec=ea-eb;
+	ed=ea-6.0*eb;
+	ee=ed+ec+ec;
+	return 3.0*sum+fac*(1.0+ed*(-C1+C5*ed-C6*delz*ee)
+		+delz*(C2*ee+delz*(-C3*ec+delz*C4*ea)))/(ave*sqrt(ave));
+}
+#undef ERRTOL
+#undef TINY
+#undef BIG
+#undef C1
+#undef C2
+#undef C3
+#undef C4
+#undef C5
+#undef C6
+#undef NRANSI