add numerical recipes library

lib/nr/ansi/examples/xgaussj.c

@@ -0,0 +1,88 @@
+
+/* Driver for routine gaussj */
+
+#include <stdio.h>
+#include <stdlib.h>
+#define NRANSI
+#include "nr.h"
+#include "nrutil.h"
+
+#define NP 20
+#define MP 20
+#define MAXSTR 80
+
+int main(void)
+{
+	int j,k,l,m,n;
+	float **a,**ai,**u,**b,**x,**t;
+	char dummy[MAXSTR];
+	FILE *fp;
+
+	a=matrix(1,NP,1,NP);
+	ai=matrix(1,NP,1,NP);
+	u=matrix(1,NP,1,NP);
+	b=matrix(1,NP,1,MP);
+	x=matrix(1,NP,1,MP);
+	t=matrix(1,NP,1,MP);
+	if ((fp = fopen("matrx1.dat","r")) == NULL)
+		nrerror("Data file matrx1.dat not found\n");
+	while (!feof(fp)) {
+		fgets(dummy,MAXSTR,fp);
+		fgets(dummy,MAXSTR,fp);
+		fscanf(fp,"%d %d ",&n,&m);
+		fgets(dummy,MAXSTR,fp);
+		for (k=1;k<=n;k++)
+			for (l=1;l<=n;l++) fscanf(fp,"%f ",&a[k][l]);
+		fgets(dummy,MAXSTR,fp);
+		for (l=1;l<=m;l++)
+			for (k=1;k<=n;k++) fscanf(fp,"%f ",&b[k][l]);
+		/* save matrices for later testing of results */
+		for (l=1;l<=n;l++) {
+			for (k=1;k<=n;k++) ai[k][l]=a[k][l];
+			for (k=1;k<=m;k++) x[l][k]=b[l][k];
+		}
+		/* invert matrix */
+		gaussj(ai,n,x,m);
+		printf("\nInverse of matrix a : \n");
+		for (k=1;k<=n;k++) {
+			for (l=1;l<=n;l++) printf("%12.6f",ai[k][l]);
+			printf("\n");
+		}
+		/* check inverse */
+		printf("\na times a-inverse:\n");
+		for (k=1;k<=n;k++) {
+			for (l=1;l<=n;l++) {
+				u[k][l]=0.0;
+				for (j=1;j<=n;j++)
+					u[k][l] += (a[k][j]*ai[j][l]);
+			}
+			for (l=1;l<=n;l++) printf("%12.6f",u[k][l]);
+			printf("\n");
+		}
+		/* check vector solutions */
+		printf("\nCheck the following for equality:\n");
+		printf("%21s %14s\n","original","matrix*sol'n");
+		for (l=1;l<=m;l++) {
+			printf("vector %2d: \n",l);
+			for (k=1;k<=n;k++) {
+				t[k][l]=0.0;
+				for (j=1;j<=n;j++)
+					t[k][l] += (a[k][j]*x[j][l]);
+				printf("%8s %12.6f %12.6f\n"," ",
+					b[k][l],t[k][l]);
+			}
+		}
+		printf("***********************************\n");
+		printf("press RETURN for next problem:\n");
+		(void) getchar();
+	}
+	fclose(fp);
+	free_matrix(t,1,NP,1,MP);
+	free_matrix(x,1,NP,1,MP);
+	free_matrix(b,1,NP,1,MP);
+	free_matrix(u,1,NP,1,NP);
+	free_matrix(ai,1,NP,1,NP);
+	free_matrix(a,1,NP,1,NP);
+	return 0;
+}
+#undef NRANSI