add numerical recipes library

lib/nr/ansi/examples/xran.c

@@ -0,0 +1,57 @@
+
+/* Driver for routines ran0, ran1, ran2, ran3 */
+
+#include <stdio.h>
+#include <math.h>
+#define NRANSI
+#include "nr.h"
+
+#define PI 3.1415926
+
+static unsigned long twotoj[16]={0x1L,0x2L,0x4L,0x8L,0x10L,0x20L,0x40L,0x80L,
+	0x100L,0x200L,0x400L,0x800L,0x1000L,0x2000L,0x4000L,0x8000L};
+
+float fnc(float x1,float x2,float x3,float x4)
+{
+	return (float) sqrt(x1*x1+x2*x2+x3*x3+x4*x4);
+}
+
+void integ(float (*func)(long *))
+{
+	long idum=(-1),iy[4],jpower,k;
+	int i,j;
+	float x1,x2,x3,x4,yprob[4];
+
+	/* Calculates pi statistically using volume of unit n-sphere */
+	for (i=1;i<=3;i++) iy[i]=0;
+	printf("volume of unit n-sphere, n = 2, 3, 4\n");
+	printf("# points      pi        (4/3)*pi    (1/2)*pi^2\n\n");
+	for (j=1;j<=15;j++) {
+		for (k=twotoj[j-1];k>=0;k--) {
+			x1=(*func)(&idum);
+			x2=(*func)(&idum);
+			x3=(*func)(&idum);
+			x4=(*func)(&idum);
+			if (fnc(x1,x2,0.0,0.0) < 1.0) ++iy[1];
+			if (fnc(x1,x2,x3,0.0) < 1.0) ++iy[2];
+			if (fnc(x1,x2,x3,x4) < 1.0) ++iy[3];
+		}
+		jpower=twotoj[j];
+		for (i=1;i<=3;i++)
+			yprob[i]=(float) twotoj[i+1]*iy[i]/jpower;
+		printf("%6ld %12.6f %12.6f %12.6f\n",
+			jpower,yprob[1],yprob[2],yprob[3]);
+	}
+	printf("\nactual %12.6f %12.6f %12.6f\n",
+		PI,4.0*PI/3.0,0.5*PI*PI);
+}
+
+int main(void)
+{
+	printf("\nTesting ran0:\n"); integ(ran0);
+	printf("\nTesting ran1:\n"); integ(ran1);
+	printf("\nTesting ran2:\n"); integ(ran2);
+	printf("\nTesting ran3:\n"); integ(ran3);
+	return 0;
+}
+#undef NRANSI