X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?p=ginac.git;a=blobdiff_plain;f=check%2Ftime_lw_H.cpp;h=c9e30c0080710c3b47074d43e97f7a1bb5fac4a5;hp=8ea4b47fa79d0c71e82e72a5fa86b50ab20b9df9;hb=8ce440866e23bd6e534131b117fd6ec34484e5e5;hpb=af922d5eb36ed70e4a9e3ffaf4c24492cf89a1a6

diff --git a/check/time_lw_H.cpp b/check/time_lw_H.cpp
index 8ea4b47f..c9e30c00 100644
--- a/check/time_lw_H.cpp
+++ b/check/time_lw_H.cpp
@@ -4,7 +4,7 @@
  *  Lewis and Michael Wester. */
 
 /*
- *  GiNaC Copyright (C) 1999-2000 Johannes Gutenberg University Mainz, Germany
+ *  GiNaC Copyright (C) 1999-2004 Johannes Gutenberg University Mainz, Germany
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -23,40 +23,54 @@
 
 #include "times.h"
 
-static unsigned test(void)
+static unsigned test(unsigned n)
 {
-	matrix h80(80,80);
-	
-	for (unsigned r=0; r<80; ++r)
-		for (unsigned c=0; c<80; ++c)
-			h80.set(r,c,numeric(1,r+c+1));
-	ex det = h80.determinant();
+	matrix hilbert(n,n);
+
+	for (unsigned r=0; r<n; ++r)
+		for (unsigned c=0; c<n; ++c)
+			hilbert.set(r,c,numeric(1,r+c+1));
+	ex det = hilbert.determinant();
+
+	/*
+	   The closed form of the determinant of n x n Hilbert matrices is:
 	
-	if (abs(det.evalf()-numeric(".10097939769690107E-3789"))>numeric("1.E-3800")) {
-		clog << "determinant of 80x80 erroneously returned " << det << endl;
+             n-1   /                   \
+            ----- | pow(factorial(r),3) |
+             | |  | ------------------- |
+             | |  |    factorial(r+n)   |
+            r = 0  \                   /
+	*/
+
+	ex hilbdet = 1;
+	for (unsigned r=0; r<n; ++r)
+		hilbdet *= pow(factorial(r),3)/(factorial(r+n));
+
+	if (det != hilbdet) {
+		clog << "determinant of " << n << "x" << n << " erroneously returned " << det << endl;
 		return 1;
 	}
 	return 0;
 }
 
-unsigned time_lw_H(void)
+unsigned time_lw_H()
 {
 	unsigned result = 0;
 	unsigned count = 0;
 	timer rolex;
 	double time = .0;
-	
+
 	cout << "timing Lewis-Wester test H (det of 80x80 Hilbert)" << flush;
-	clog << "-------Lewis-Wester test H (det of 80x80 Hilbert)" << endl;
-	
+	clog << "-------Lewis-Wester test H (det of 80x80 Hilbert):" << endl;
+
 	rolex.start();
 	// correct for very small times:
 	do {
-		result = test();
+		result = test(80);
 		++count;
 	} while ((time=rolex.read())<0.1 && !result);
 	cout << '.' << flush;
-	
+
 	if (!result) {
 		cout << " passed ";
 		clog << "(no output)" << endl;
@@ -64,6 +78,6 @@ unsigned time_lw_H(void)
 		cout << " failed ";
 	}
 	cout << int(1000*(time/count))*0.001 << 's' << endl;
-	
+
 	return result;
 }