X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?p=ginac.git;a=blobdiff_plain;f=check%2Ftime_lw_H.cpp;h=1621a6e117e69d7da938a69dfa4af0cd5bf7f885;hp=1bbe19d9e0d2ab21e23bd6bdf1fae50fafc6ee1d;hb=6e3e0fec75584b29ad6a18734e52d249dccc2a36;hpb=a54293fb33b252ca926cd1aba18faacb0f16688a

diff --git a/check/time_lw_H.cpp b/check/time_lw_H.cpp
index 1bbe19d9..1621a6e1 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) 1999-2001 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
@@ -23,47 +23,62 @@
 
 #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();
-    
-    if (abs(det.evalf()-numeric(".10097939769690107E-3789"))>numeric("1.E-3800")) {
-        clog << "determinant of 80x80 erroneously returned " << det << endl;
-        return 1;
-    }
-    return 0;
+	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:
+	//
+	//      n-1   /                      n-1                 \
+	//     ----- |                      -----                 |
+	//      | |  | pow(factorial(r),2)   | |    hilbert(r,c)  |
+	//      | |  |                       | |                  |   
+	//     r = 0  \                     c = 0                /
+	
+	ex hilbdet = 1;
+	for (unsigned r=0; r<n; ++r) {
+		hilbdet *= pow(factorial(numeric(r)),2);
+		for (unsigned c=0; c<n; ++c)
+			hilbdet *= hilbert(r,c);
+	}
+	
+	if (det != hilbdet) {
+		clog << "determinant of " << n << "x" << n << " erroneously returned " << det << endl;
+		return 1;
+	}
+	return 0;
 }
 
 unsigned time_lw_H(void)
 {
-    unsigned result = 0;
-    unsigned count = 1;
-    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;
-    
-    rolex.start();
-    // correct for very small times:
-    do {
-        result = test();
-        ++count;
-    } while ((time=rolex.read())<0.1 && !result);
-    cout << '.' << flush;
-    
-    if (!result) {
-        cout << " passed ";
-        clog << "(no output)" << endl;
-    } else {
-        cout << " failed ";
-    }
-    cout << int(1000*(time/count))*0.001 << 's' << endl;
-    
-    return result;
+	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;
+	
+	rolex.start();
+	// correct for very small times:
+	do {
+		result = test(80);
+		++count;
+	} while ((time=rolex.read())<0.1 && !result);
+	cout << '.' << flush;
+	
+	if (!result) {
+		cout << " passed ";
+		clog << "(no output)" << endl;
+	} else {
+		cout << " failed ";
+	}
+	cout << int(1000*(time/count))*0.001 << 's' << endl;
+	
+	return result;
 }