Posted by Don Visco on June 19, 1998 at 15:30:36:

I need to accurately invert a 108 x 108 real,

non-symmetric matrix. Currently I am using the

LU decomposition routine in Numerical Recipes but

when I check the inverse I find that some of the

off-diagonal elements are not zero. In fact,

the last two rows have elements which are in the thousands.

When I ran the code using the -d16 switch on F90, the

problem went away but it took about 15 times longer.

I tried iterative improvement but that doesn't help.

Any suggestions on a robust algorithm which does not require

the -d16 switch. Please e-mail me directly if you don't mind.

Thanks!

- Re: Inverting a Matrix
**Massimo gaspari***06:49:26 6/25/98*(0)