From: Minkoo Seo <minkoo.seo@gmail.com> [code snipped]

for (unsigned i = 0; i < 3; i++) m(i, i) = -i;

In this code, I'm trying to initialize the diagonal with -1, -2, -3. But, the result is obviously different from what I expected:

[3,3]((0,0,0),(0,4.29497e+09,0),(0,0,4.29497e+09))

If you must use unsigned, then change to: m(i, i) = -1.0 * static_cast<double>(i); What it's doing now is this: i = 1; -i = 4294967295; // it's unsigned, after all double(-i) = 4.295e+9 Probably clearer to use int instead of unsigned, though. - James Jones Administrative Data Mgmt. Webmaster 375 Raritan Center Pkwy, Suite A Data Architect Edison, NJ 08837