PolyInterpMixin<time>::fas() function question

Parallel-in-Time / PFASST

PFASST++ is a C++ implementation of the "parallel full approximation scheme in space and time" (PFASST) algorithm

http://www.parallelintime.org/PFASST/

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PolyInterpMixin<time>::fas() function question #249

Closed meiyuanzhen closed 1 year ago

meiyuanzhen commented 1 year ago

The function PolyInterpMixin::fas(...) in file poly_interp_impl.hpp is the function to compute FAS correction 'tau' iterm. In this function, the matrix fmat seems to have rows like [ -1 -1 -1 1 | 1 1 1 -1], which is confusing. I thought this should be like [0 0 -1 1 | 0 0 1 -1] to compute an interval quadrature. There should be something I misunderstood, so please give me some clue. Looking forward to any reply.

pancetta commented 1 year ago

H! Thanks for reaching out. This project is somewhat outdated, I have to admit. Did you verify that fmat has these rows? The loop looks confusing and redundant in parts, so I'm not sure this is what you get. Did it work (better) with your fmat?

meiyuanzhen commented 1 year ago

Thank you for your reply. I have tried with my fmat and obtained similar results as the original fmat, so the influence is essential but not huge. Currently I am using another code to perform PFASST, and I found I should follow the updated PFASST method rather than the original paper. Therefore, I could misunderstood your code and I am still studing the new code and figuring out the algorithm. Again, thanks for you reply!