# How can I tell VASP 5.2 is compiled with FFTW3?

When VASP 5 was released, the performance was mostly slower than our make of VASP 4.6. I wrote it off as an optimization issue, and went on in my life. Then, in VASP 5.2, with the release notes, I realized that the it was all due to slower FFT, and is now fixed. Is there any way for me, as a user, to tell if the VASP make that I am using is built with the faster FFTW?

• If you are still working with VASP and run into any questions, you might be interested in Matter Modeling SE Nov 11 at 16:40

• To expand on this answer, you could also try: nm vasp | grep fftw to take a look for some of the FFTW symbols assuming that the executable hasn't been stripped. Nov 30 '11 at 13:13
• That's a great point, Aron, though I recommend grep -i in this context. Dec 2 '11 at 15:04