add numerical recipes library

lib/nr/k_and_r/recipes/sprsin.c

@@ -0,0 +1,26 @@
+
+#include <math.h>
+
+void sprsin(a,n,thresh,nmax,sa,ija)
+float **a,sa[],thresh;
+int n;
+unsigned long ija[],nmax;
+{
+	void nrerror();
+	int i,j;
+	unsigned long k;
+
+	for (j=1;j<=n;j++) sa[j]=a[j][j];
+	ija[1]=n+2;
+	k=n+1;
+	for (i=1;i<=n;i++) {
+		for (j=1;j<=n;j++) {
+			if (fabs(a[i][j]) >= thresh && i != j) {
+				if (++k > nmax) nrerror("sprsin: nmax too small");
+				sa[k]=a[i][j];
+				ija[k]=j;
+			}
+		}
+		ija[i+1]=k+1;
+	}
+}