fix(SWFFT/Poisson) #534

Job	Run time
Clang@6.0 C++14 SP Particles DP Mesh Debug [tutorials]	7m 4s
Clang@6.0 C++14 SP Particles DP Mesh Debug [tutorials]	7m 2s
Clang@6.0 C++14 SP Particles DP Mesh Debug [tutorials]	7m 19s
GNU@7.5 C++14 [tutorials]	10m 57s
GNU@7.5 C++14 [tutorials]	10m 47s
GNU@7.5 C++14 [tutorials]	11m 18s
GNU@10.3 C++20 OMP [tutorials]	11m 45s
GNU@10.3 C++20 OMP [tutorials]	11m 26s
GNU@10.3 C++20 OMP [tutorials]	11m 28s
CUDA@11.2 GNU@9.3.0 C++17 Release [tutorials]	30m 32s
CUDA@11.2 GNU@9.3.0 C++17 Release [tutorials]	30m 32s
CUDA@11.2 GNU@9.3.0 C++17 Release [tutorials]	30m 32s
GNU@7.5 C++14 w/o Fortran [tutorials]	8m 35s
GNU@7.5 C++14 w/o Fortran [tutorials]	8m 29s
GNU@7.5 C++14 w/o Fortran [tutorials]	9m 7s
GNU@7.5 C++14 NOMPI [tutorials]	9m 56s
GNU@7.5 C++14 NOMPI [tutorials]	9m 20s
GNU@7.5 C++14 NOMPI [tutorials]	9m 42s
DPCPP GFortran@7.5 C++17 [tutorials]	29m 27s
DPCPP GFortran@7.5 C++17 [tutorials]	29m 27s
DPCPP GFortran@7.5 C++17 [tutorials]	29m 27s
HIP ROCm GFortran@9.3 C++17 [tutorials]	1h 2m 10s
HIP ROCm GFortran@9.3 C++17 [tutorials]	1h 2m 10s
HIP ROCm GFortran@9.3 C++17 [tutorials]	1h 2m 10s
	8h 30m 42s

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