### general eigen solver ZGGEV problem compared with NAG

Posted:

**Mon May 22, 2006 12:13 pm**I am trying to use the lapack routine ZGGEV to comput the eigen value lamada of A*X=lamba*B*X with A and B complex*16 non-symmetric matrix. But the error info indicate The QZ iteration failed for some sets of A and B.

In my problem, I calculate 148 sets of different A and B for lamada. If I use the NAG subroutine F02GJF(), then all sets of A and B return correct eigen values. But if I tried the lapack routine ZGGEV (by Intel MKL), then only 36 sets return correct eigen value, and the others have error info which indicate failure in the QZ interation. I also tried the lapack routine ZGGEV provided by AMD's ACML library, then 72 sets of A and B return correct eigenvalue and the others also return the error info which indicate failure in the QZ interation.

I tried to adjust the work space size to optimal condiation, but no improvment for the perfomance.

Any suggestion to solve this problem?

Thank you very much!!

Milton

In my problem, I calculate 148 sets of different A and B for lamada. If I use the NAG subroutine F02GJF(), then all sets of A and B return correct eigen values. But if I tried the lapack routine ZGGEV (by Intel MKL), then only 36 sets return correct eigen value, and the others have error info which indicate failure in the QZ interation. I also tried the lapack routine ZGGEV provided by AMD's ACML library, then 72 sets of A and B return correct eigenvalue and the others also return the error info which indicate failure in the QZ interation.

I tried to adjust the work space size to optimal condiation, but no improvment for the perfomance.

Any suggestion to solve this problem?

Thank you very much!!

Milton