Hi Lawrence,
Could there be an overhead from loading the LAPACK library, which is required for the LU solve?
This isn't how dynamic loading works. The first time you load the .so, in the warmup phase, the symbol is resolved, and the trampoline is replaced by a direct call.
Yes, that's what I also thought, just wanted to double check.
I have effectively no idea what's going on. Does the LU solve take this long on this much data if you just call it from C?
I agree, that seems to be the obvious test to do. Maybe there is something strange going on in the LAPACK. I will have a go at that, and see if I get exactly the same time as if I run it through firedrake.
IOW, I think it's not "our" fault, unless somehow you're managing to get a recompile or similar every time you call _lu_solve.
Lawrence
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