add numerical recipes library

lib/nr/ansi/recipes/bandec.c

@@ -0,0 +1,47 @@
+
+#include <math.h>
+#define SWAP(a,b) {dum=(a);(a)=(b);(b)=dum;}
+#define TINY 1.0e-20
+
+void bandec(float **a, unsigned long n, int m1, int m2, float **al,
+	unsigned long indx[], float *d)
+{
+	unsigned long i,j,k,l;
+	int mm;
+	float dum;
+
+	mm=m1+m2+1;
+	l=m1;
+	for (i=1;i<=m1;i++) {
+		for (j=m1+2-i;j<=mm;j++) a[i][j-l]=a[i][j];
+		l--;
+		for (j=mm-l;j<=mm;j++) a[i][j]=0.0;
+	}
+	*d=1.0;
+	l=m1;
+	for (k=1;k<=n;k++) {
+		dum=a[k][1];
+		i=k;
+		if (l < n) l++;
+		for (j=k+1;j<=l;j++) {
+			if (fabs(a[j][1]) > fabs(dum)) {
+				dum=a[j][1];
+				i=j;
+			}
+		}
+		indx[k]=i;
+		if (dum == 0.0) a[k][1]=TINY;
+		if (i != k) {
+			*d = -(*d);
+			for (j=1;j<=mm;j++) SWAP(a[k][j],a[i][j])
+		}
+		for (i=k+1;i<=l;i++) {
+			dum=a[i][1]/a[k][1];
+			al[k][i-k]=dum;
+			for (j=2;j<=mm;j++) a[i][j-1]=a[i][j]-dum*a[k][j];
+			a[i][mm]=0.0;
+		}
+	}
+}
+#undef SWAP
+#undef TINY