FEniCS / ffcx / 32232180130

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main: 85%

Build Type

Pull #859

github

Committed by garth-wells

Commit Message

Only split the quadrature loop when it has a math function to vectorise

#852 splits the quadrature loop into an evaluation pass and a
contraction pass whenever any fw intermediate exists, so that vectorised
math-library calls (sin, exp, ...) can escape the strided contraction
loop. But an fw intermediate exists for almost every integral -- even a
bare mass matrix has one (the quadrature weight times |detJ|) -- and
when there is nothing to unblock, the split is pure overhead: an extra
loop plus a store/load of every fw through a cache array.

Benchmarked across ten forms on top of this branch (mass matrix, vector
Poisson, elasticity, Taylor-Hood Stokes, N1curl mass, SIPG DG,
HyperElasticity), the unconditional split regresses math-function-free
forms by up to 11-13% at -O2 while leaving the forms #852 targets fully
intact.

Gate the split on the evaluation code actually containing a
MathFunction call, matching the open question raised in #852's own
description. Closes the regression on math-function-free forms (mass
matrix: 0.89x -> 0.99x at -O2) at no cost to the cases #852 targets.
`pytest test/` passes: 46 passed, 1 skipped (unchanged from this
branch).

AI assistance: I used Claude Code (Opus 5) to draft this change,
building on #852. I reviewed and take responsibility for the final
contribution.

Pull Request Pull Request #859: Only split the quadrature loop when it has a math function to vectorise

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