add numerical recipes library

lib/nr/ansi/examples/xirbit2.c

@@ -0,0 +1,41 @@
+
+/* Driver for routine irbit2 */
+
+#include <stdio.h>
+#define NRANSI
+#include "nr.h"
+
+#define NBIN 15
+#define NTRIES 10000
+
+static unsigned long twoton[16]={0x1L,0x2L,0x4L,0x8L,0x10L,0x20L,0x40L,0x80L,
+	0x100L,0x200L,0x400L,0x800L,0x1000L,0x2000L,0x4000L,0x8000L};
+
+int main(void)
+{
+	int i,iflg,ipts=0,j,n;
+	unsigned long iseed=111;
+	float delay[NBIN+1];
+
+	/* Calculate distribution of runs of zeros */
+	for (i=1;i<=NBIN;i++) delay[i]=0.0;
+	for (i=1;i<=NTRIES;i++) {
+		if (irbit2(&iseed) == 1) {
+			++ipts;
+			iflg=0;
+			for (j=1;j<=NBIN;j++) {
+				if ((irbit2(&iseed) == 1) && (iflg == 0)) {
+					iflg=1;
+					++delay[j];
+				}
+			}
+		}
+	}
+	printf("distribution of runs of n zeros\n");
+	printf("%6s %22s %18s \n","n","probability","expected");
+	for (n=1;n<=NBIN;n++)
+		printf("%6d %19.4f %20.4f\n",
+			(n-1),delay[n]/ipts,1.0/(double)twoton[n]);
+	return 0;
+}
+#undef NRANSI