- clarify comment about counterintuitive sorting for Laplace.

diff --git a/ginac/matrix.cpp b/ginac/matrix.cpp
index c48fb6b124bc99b090e3e4961c5a795cf71ae8a8..e544210f32c75b01ee3f8ff2582a160157e01f18 100644 (file)
--- a/ginac/matrix.cpp
+++ b/ginac/matrix.cpp
@@ -772,10 +772,13 @@ ex matrix::determinant(unsigned algo) const
                default: {
                        // This is the minor expansion scheme.  We always develop such
                        // that the smallest minors (i.e, the trivial 1x1 ones) are on the
-                       // rightmost column.  For this to be efficient it turns out that
-                       // the emptiest columns (i.e. the ones with most zeros) should be
-                       // the ones on the right hand side.  Therefore we presort the
-                       // columns of the matrix:
+                       // rightmost column.  For this to be efficient, empirical tests
+                       // have shown that the emptiest columns (i.e. the ones with most
+                       // zeros) should be the ones on the right hand side -- although
+                       // this might seem counter-intuitive (and in contradiction to some
+                       // literature like the FORM manual).  Please go ahead and test it
+                       // if you don't believe me!  Therefore we presort the columns of
+                       // the matrix:
                        typedef std::pair<unsigned,unsigned> uintpair;
                        std::vector<uintpair> c_zeros;  // number of zeros in column
                        for (unsigned c=0; c<col; ++c) {