add numerical recipes library

lib/nr/k_and_r/recipes/rstrct.c

@@ -0,0 +1,22 @@
+
+void rstrct(uc,uf,nc)
+double **uc,**uf;
+int nc;
+{
+	int ic,iif,jc,jf,ncc=2*nc-1;
+
+	for (jf=3,jc=2;jc<nc;jc++,jf+=2) {
+		for (iif=3,ic=2;ic<nc;ic++,iif+=2) {
+			uc[ic][jc]=0.5*uf[iif][jf]+0.125*(uf[iif+1][jf]+uf[iif-1][jf]
+					+uf[iif][jf+1]+uf[iif][jf-1]);
+		}
+	}
+	for (jc=1,ic=1;ic<=nc;ic++,jc+=2) {
+		uc[ic][1]=uf[jc][1];
+		uc[ic][nc]=uf[jc][ncc];
+	}
+	for (jc=1,ic=1;ic<=nc;ic++,jc+=2) {
+		uc[1][ic]=uf[1][jc];
+		uc[nc][ic]=uf[ncc][jc];
+	}
+}