fft_physical_x

Test FFT for X pencil decomposition

List of the tests:

• fft_c2c_x: Test Complex to Complex FFT transform;
• fft_r2c_x: Test Real to Complex FFT transform;
• fft_grid_x: Test Real to Complex transform of a different grid than the one used for the initialization.

These programs can be used to test the FFT transform using X-pencils as starting domain decomposition. Both c2c (fft_c2c_x) and r2c/c2r (fft_r2c_x) transforms are tested. The case fft_grod uses a different resolution from the one used for the initialization. The results should recover the input data up to machine accuracy after a forward and a backward transform and appropriate normalisation. The test automatically resize the problem depending on the number of MPI processes in use

What to input: The program takes max 6 inputs as :

1. p_row [optional]
2. p_col [optional]
3. nx [optional]
4. ny [optional]
5. nz [optional]
6. nt [optional]

If the decomposition is imposed both (1) and (2) are necessary. If the resolution is imposed (1-5) are necessary

What to expect:

• The timing results
• The error reported should be around machine accuracy (~ 10^-6 for single precision and 10^-15 for double)
• In case of the GENERIC FFT expect an increase in the order of the error