jerro:
Are all your benchmarks done on a 64 bit system?
I think what Phobos does in
this case is wrong. The fact that one class works on all
floating point types results in very poor precision when
the data consists of doubles or reals. I guess that precomputed
tables are stored as floats. You could only fix that by saving
them as reals, but that would probably hurt performance quite
a lot. The fact that one instance can be used for multiple sizes
would be a problem if we wanted to change an implementation
since
not all FFT implementation can use one precomputed table for
different data sizes.
If you are right and this is a problem, are Andrei and others
accepting to change this little part of Phobos? If the answer is
positive, are you interested in creating a GIT patch that changes
that?
Bye,
bearophile
