add numerical recipes library

lib/nr/ansi/examples/xtridag.c

@@ -0,0 +1,72 @@
+
+/* Driver for routine tridag */
+
+#include <stdio.h>
+#include <stdlib.h>
+#define NRANSI
+#include "nr.h"
+#include "nrutil.h"
+
+#define NP 20
+#define MAXSTR 80
+
+int main(void)
+{
+	unsigned long k,n;
+	float *diag,*superd,*subd,*rhs,*u;
+	char dummy[MAXSTR];
+	FILE *fp;
+
+	diag=vector(1,NP);
+	superd=vector(1,NP);
+	subd=vector(1,NP);
+	rhs=vector(1,NP);
+	u=vector(1,NP);
+	if ((fp = fopen("matrx2.dat","r")) == NULL)
+		nrerror("Data file matrx2.dat not found\n");
+	while (!feof(fp)) {
+		fgets(dummy,MAXSTR,fp);
+		fgets(dummy,MAXSTR,fp);
+		fscanf(fp,"%ld ",&n);
+		fgets(dummy,MAXSTR,fp);
+		for (k=1;k<=n;k++) fscanf(fp,"%f ",&diag[k]);
+		fgets(dummy,MAXSTR,fp);
+		for (k=1;k<n;k++) fscanf(fp,"%f ",&superd[k]);
+		fgets(dummy,MAXSTR,fp);
+		for (k=2;k<=n;k++) fscanf(fp,"%f ",&subd[k]);
+		fgets(dummy,MAXSTR,fp);
+		for (k=1;k<=n;k++) fscanf(fp,"%f ",&rhs[k]);
+		/* carry out solution */
+		tridag(subd,diag,superd,rhs,u,n);
+		printf("\nThe solution vector is:\n");
+		for (k=1;k<=n;k++) printf("%12.6f",u[k]);
+		printf("\n");
+		/* test solution */
+		printf("\n(matrix)*(sol'n vector) should be:\n");
+		for (k=1;k<=n;k++) printf("%12.6f",rhs[k]);
+		printf("\n");
+		printf("actual result is:\n");
+		for (k=1;k<=n;k++) {
+			if (k == 1)
+				rhs[k]=diag[1]*u[1]+superd[1]*u[2];
+			else if (k == n)
+				rhs[k]=subd[n]*u[n-1]+diag[n]*u[n];
+			else
+				rhs[k]=subd[k]*u[k-1]+diag[k]*u[k]
+					+superd[k]*u[k+1];
+		}
+		for (k=1;k<=n;k++) printf("%12.6f",rhs[k]);
+		printf("\n");
+		printf("***********************************\n");
+		printf("press return for next problem:\n");
+		(void) getchar();
+	}
+	fclose(fp);
+	free_vector(u,1,NP);
+	free_vector(rhs,1,NP);
+	free_vector(subd,1,NP);
+	free_vector(superd,1,NP);
+	free_vector(diag,1,NP);
+	return 0;
+}
+#undef NRANSI