> > This is probably platform and release dependent. On my WinXP laptop running R2012a, the top row (using ifft) takes <3secs, whereas the second (fft with 2 conjs) takes 4.5 secs. Your results may possibly be due to a different BLAS version on your system. Try running on other releases/platforms. >
Actually I verified that it is load dependent. My test was for a 12 cores workstation (Matlab R2009b) close to full load (11 cores active). If I run Matlab with the option -singleCompThread I have comparable values to yours, i.e., standard ifft is the best option. Thanks.