add numerical recipes library

lib/nr/ansi/examples/xbsstep.c

@@ -0,0 +1,54 @@
+
+/* Driver for routine bsstep */
+
+#include <stdio.h>
+#define NRANSI
+#include "nr.h"
+#include "nrutil.h"
+
+#define N 4
+
+float dxsav,*xp,**yp;   /* defining declarations */
+int kmax,kount;
+
+int nrhs;   /* counts function evaluations */
+
+void derivs(float x,float y[],float dydx[])
+{
+	nrhs++;
+	dydx[1] = -y[2];
+	dydx[2]=y[1]-(1.0/x)*y[2];
+	dydx[3]=y[2]-(2.0/x)*y[3];
+	dydx[4]=y[3]-(3.0/x)*y[4];
+}
+
+int main(void)
+{
+	int i,nbad,nok;
+	float eps=1.0e-4,h1=0.1,hmin=0.0,x1=1.0,x2=10.0,*ystart;
+
+	ystart=vector(1,N);
+	xp=vector(1,200);
+	yp=matrix(1,10,1,200);
+	ystart[1]=bessj0(x1);
+	ystart[2]=bessj1(x1);
+	ystart[3]=bessj(2,x1);
+	ystart[4]=bessj(3,x1);
+	nrhs=0;
+	kmax=100;
+	dxsav=(x2-x1)/20.0;
+	odeint(ystart,N,x1,x2,eps,h1,hmin,&nok,&nbad,derivs,bsstep);
+	printf("\n%s %13s %3d\n","successful steps:"," ",nok);
+	printf("%s %20s %3d\n","bad steps:"," ",nbad);
+	printf("%s %9s %3d\n","function evaluations:"," ",nrhs);
+	printf("\n%s %3d\n","stored intermediate values:    ",kount);
+	printf("\n%8s %18s %15s\n","x","integral","bessj(3,x)");
+	for (i=1;i<=kount;i++)
+		printf("%10.4f %16.6f %14.6f\n",
+			xp[i],yp[4][i],bessj(3,xp[i]));
+	free_matrix(yp,1,10,1,200);
+	free_vector(xp,1,200);
+	free_vector(ystart,1,N);
+	return 0;
+}
+#undef NRANSI