- replaced dumb consistency check by a rigorous one.

diff --git a/check/time_vandermonde.cpp b/check/time_vandermonde.cpp
index f878b0b886ddc398355b836d97e694852838e61e..b190e218030c2972911ffcdcf619ba112932cc57 100644 (file)
--- a/check/time_vandermonde.cpp
+++ b/check/time_vandermonde.cpp
@@ -30,29 +30,34 @@ static unsigned vandermonde_det(unsigned size)
 {
        unsigned result = 0;
        symbol a("a");
-       
+
        // construct Vandermonde matrix:
        matrix M(size,size);
        for (unsigned ro=0; ro<size; ++ro) {
                for (unsigned co=0; co<size; ++co) {
                        if (ro%2)
-                               M.set(ro,co,pow(-pow(a,1+ro/2),co));
+                               M(ro,co) = pow(-pow(a,1+ro/2),co);
                        else
-                               M.set(ro,co,pow(pow(a,1+ro/2),co));
+                               M(ro,co) = pow(pow(a,1+ro/2),co);
                }
        }
-       
+
        // compute determinant:
-       ex vdet = M.determinant();
-       
-       // dirty consistency check of result:
-       if (!vdet.subs(a==1).is_zero()) {
+       ex det = M.determinant();
+
+       // check the result:
+       ex vanddet = 1;
+       for (unsigned i=0; i<size; ++i)
+               for (unsigned j=0; j<i; ++j)
+                       vanddet *= M(i,1) - M(j,1);
+
+       if (expand(det - vanddet) != 0) {
                clog << "Determaint of Vandermonde matrix " << endl
                     << "M==" << M << endl
-                    << "was miscalculated: det(M)==" << vdet << endl;
+                    << "was miscalculated: det(M)==" << det << endl;
                ++result;
        }
-       
+
        return result;
 }