add numerical recipes library

lib/nr/cpp/recipes/slvsm2.cpp

@@ -0,0 +1,16 @@
+#include <cmath>
+#include "nr.h"
+using namespace std;
+
+void NR::slvsm2(Mat_O_DP &u, Mat_I_DP &rhs)
+{
+	int i,j;
+	DP disc,fact,h=0.5;
+
+	for (i=0;i<3;i++)
+		for (j=0;j<3;j++)
+			u[i][j]=0.0;
+	fact=2.0/(h*h);
+	disc=sqrt(fact*fact+rhs[1][1]);
+	u[1][1]= -rhs[1][1]/(fact+disc);
+}