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Dear all,<br><br>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.<br>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?<br>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?<br><br>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?<br><br>Thank you in advance for your helpfulness.<br>Sincerely,<br><br> Marco Mazzuoli<br><pre><font style="font-size:10pt" color="#002060" size="2"><br><br>Ing. Marco Mazzuoli</font><font style="font-size:10pt" color="#002060" size="2"><br></font><font style="font-size:10pt" color="#002060" size="2">Dipartimento di Ingegneria</font><font style="font-size:10pt" color="#002060" size="2"><br></font><font style="font-size:10pt" color="#002060" size="2">delle Costruzioni, dell'Ambiente e</font><font style="font-size:10pt" color="#002060" size="2"><br></font><font style="font-size:10pt" color="#002060" size="2">del Territorio (DICAT)</font><font style="font-size:10pt" color="#002060" size="2"><br></font><font style="font-size:10pt" color="#002060" size="2">via Montallegro 1</font><font style="font-size:10pt" color="#002060" size="2"><br></font><font style="font-size:10pt" color="#002060" size="2">16145 GENOVA-ITALY</font><font style="font-size:10pt" color="#002060" size="2"><br></font><font style="font-size:10pt" color="#002060" size="2">tel. +39 010 353 2497</font><font style="font-size:10pt" color="#002060" size="2"><br>cell. +39 338 7142904<br></font><font style="font-size:10pt" color="#002060" size="2">e-mail marco.mazzuoli@unige.it</font><font style="font-size:10pt" color="#002060" size="2"><br></font><font style="font-size:10pt" color="#002060" size="2"> marco.mazzuoli84@gmail.com<br></font><font style="font-size:10pt" size="2"><img alt=""></font><br><br><br><br></pre> </div></body>
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