my $dmat = pdl [
	       [4, 2, 9, 7],
	       [2, 5, 5, 4],
	       [6, 3, 5, 3],
	       [8, 4, 6, 6],
	       ];

my $damat = pdl [
	       [21, 2, 9, 7],
	       [11.5, 5, 5, 4],
	       [15.5, 3, 5, 3],
	       [22, 4, 6, 6],
	       ];

my $dbmat = pdl [
	       [4, 21, 9, 7],
	       [2, 11.5, 5, 4],
	       [6, 15.5, 5, 3],
	       [8, 22, 6, 6],
	       ];

my $dcmat = pdl [
	       [4, 2, 21, 7],
	       [2, 5, 11.5, 4],
	       [6, 3, 15.5, 3],
	       [8, 4, 22, 6],
	       ];

my $ddmat = pdl [
	       [4, 2, 9, 21],
	       [2, 5, 5, 11.5],
	       [6, 3, 5, 15.5],
	       [8, 4, 6, 22],
	       ];