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=1621a6e117e69d7da938a69dfa4af0cd5bf7f885;hb=8ce440866e23bd6e534131b117fd6ec34484e5e5;hpb=6e3e0fec75584b29ad6a18734e52d249dccc2a36

diff --git a/check/time_lw_H.cpp b/check/time_lw_H.cpp
index 1621a6e1..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) 1999-2001 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
@@ -26,27 +26,26 @@
 static unsigned test(unsigned n)
 {
 	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:
 	
-	// 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                /
-	
+             n-1   /                   \
+            ----- | pow(factorial(r),3) |
+             | |  | ------------------- |
+             | |  |    factorial(r+n)   |
+            r = 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);
-	}
-	
+	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;
@@ -54,16 +53,16 @@ static unsigned test(unsigned n)
 	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 {
@@ -71,7 +70,7 @@ unsigned time_lw_H(void)
 		++count;
 	} while ((time=rolex.read())<0.1 && !result);
 	cout << '.' << flush;
-	
+
 	if (!result) {
 		cout << " passed ";
 		clog << "(no output)" << endl;
@@ -79,6 +78,6 @@ unsigned time_lw_H(void)
 		cout << " failed ";
 	}
 	cout << int(1000*(time/count))*0.001 << 's' << endl;
-	
+
 	return result;
 }