I am running ARPACK to diagonalize matrices. ARPACK is packaged with LAPACK 2.0 which is the current bottleneck in the program. I would like to be able to use a modern and ultimately threaded version of LAPACK. I have tried LAPACK 3.4 and 3.0, but the results are not the same. Modern BLAS works fine.

It's a long shot, but is there any way to find out what has changed since 2.0?

The eigenvalue results that I get are not completely wrong, so the change is probably subtle, perhaps a slightly altered mathematical definition? Aside from this, I have no further insight.

Thanks