Hi, sorry i haven't answered in a while. >> i was wondering if there is an implementation of parallel qr decomposition in PETSc. > For what purpose do you need a QR? We may have suggestions if we know how you want to use it. I found an interesting algorithm for radial basis function interpolation. It mitigates the ill-conditioning that arises from making radial basis functions increasingly flat. The paper can be found at https://amath.colorado.edu/faculty/fornberg/Docs/SISCmanuscript.pdf The algorithm defines a Matrix C that is rectangular (more columns than rows). Then a QR Decomposition of C is computed. It looks like this: C = Q [R1 R2] with R1 being rectangular and R2 being stacked on it horizontally. What i want to compute in the end is: R_1^{-1} R_2 Which isn't that hard to compute once R is known, as this is just backward substitution. Anyway i still need to do a full QR decomposition (Even though i don't actually need Q, it would be easy to calculate from R, so i don't think there is any shortcut to Q, except that i don't have to store Q). What i was thinking of as a possible solution is to parallelize Givens rotations by leveraging the fact that it only has local row-wise data dependencies in each step.
Best regards David Sommer
