[FLASH-USERS] Does FFT subroutine work with every domain discretization?‏‏

[Marco Mazzuoli]

    Dear all,

in the application I developed, based on the Flash 
4.0alpha architecture and the PARAMESH package, a (three-dimensional) 
Poisson problem is numerically solved by means of the multigrid method 
provided with the Flash package. Both pFFT and FFT are implemented into 
the Poisson solver. However, by making some preliminary tests, I have 
noticed that the fast Fourier transform is well performed only if the 
number of the discretization points in the three dimensions (e.g. NXB, 
NYB, NZB) is a multiple of 2.
1a) Does the FFT even work when blocks 
have a different size? Actually, it is quite common that FFT routines 
accept also array sizes which are also multiple of 3 and 5. Is it the 
case?
1b) Eventually, do you think it could be possible to replace 
the Flash's FFT with another FFT subroutine in order to support my 
request?

2) A secondary question deals with the Poisson solver. 
On the basis of Huang \& Greengard (2000) and Ricker (2008) 
algorithms, do you think it is feasible to modify the Poisson solver, 
distributed within the Flash package, in order to obtain a solver for a 
HelmHoltz problem?

Thank you in advance for your helpfulness.
Sincerely,

    Marco Mazzuoli


Ing. Marco Mazzuoli
Dipartimento di Ingegneria
delle Costruzioni, dell'Ambiente e
del Territorio (DICAT)
via Montallegro 1
16145 GENOVA-ITALY
tel.  +39 010 353 2497
cell. +39 338 7142904
e-mail marco.mazzuoli at unige.it
       marco.mazzuoli84 at gmail.com




 		 	   		  
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://flash.rochester.edu/pipermail/flash-users/attachments/20121001/4714bd01/attachment.htm>