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[ginac.git] / check / time_lw_H.cpp

diff --git a/check/time_lw_H.cpp b/check/time_lw_H.cpp
index 8ea4b47fa79d0c71e82e72a5fa86b50ab20b9df9..c9e30c0080710c3b47074d43e97f7a1bb5fac4a5 100644 (file)
--- 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;
 }