add numerical recipes library

lib/nr/k_and_r/recipes/mpmul.c

@@ -0,0 +1,46 @@
+
+#include "nrutil.h"
+#define RX 256.0
+
+void mpmul(w,u,v,n,m)
+int m,n;
+unsigned char u[],v[],w[];
+{
+	void drealft();
+	int j,mn,nn=1;
+	double cy,t,*a,*b;
+
+	mn=IMAX(m,n);
+	while (nn < mn) nn <<= 1;
+	nn <<= 1;
+	a=dvector(1,nn);
+	b=dvector(1,nn);
+	for (j=1;j<=n;j++)
+		a[j]=(double)u[j];
+	for (j=n+1;j<=nn;j++) a[j]=0.0;
+	for (j=1;j<=m;j++)
+		b[j]=(double)v[j];
+	for (j=m+1;j<=nn;j++) b[j]=0.0;
+	drealft(a,nn,1);
+	drealft(b,nn,1);
+	b[1] *= a[1];
+	b[2] *= a[2];
+	for (j=3;j<=nn;j+=2) {
+		b[j]=(t=b[j])*a[j]-b[j+1]*a[j+1];
+		b[j+1]=t*a[j+1]+b[j+1]*a[j];
+	}
+	drealft(b,nn,-1);
+	cy=0.0;
+	for (j=nn;j>=1;j--) {
+		t=b[j]/(nn>>1)+cy+0.5;
+		cy=(unsigned long) (t/RX);
+		b[j]=t-cy*RX;
+	}
+	if (cy >= RX) nrerror("cannot happen in fftmul");
+	w[1]=(unsigned char) cy;
+	for (j=2;j<=n+m;j++)
+		w[j]=(unsigned char) b[j-1];
+	free_dvector(b,1,nn);
+	free_dvector(a,1,nn);
+}
+#undef RX