SupernodalLU: route panel triangular solves through TriangularSolve (−13 to −18% refactorization)#1113
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ChrisRackauckas merged 1 commit intoJul 26, 2026
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The supernodal factorization applies two BLAS-3 trsms per supernode against its just-factored diagonal block: the L21 panel on the right by U11, and the U12 panel on the left by unit-L11. They now go through overridable hooks whose default is the stdlib triangular solve, with LinearSolveRecursiveFactorizationExt overriding them with TriangularSolve. TriangularSolve is a hard dependency of RecursiveFactorization and is what RecursiveFactorization uses for its own trsms, so this adds nothing to anyone's dependency graph: it is declared as a weakdep purely to trigger the extension, and since RecursiveFactorization pulls it in, loading RecursiveFactorization alone still activates everything. That is also exactly the condition under which RFLUFactorization becomes the dense default, so the sparse solver's panel work and the dense default run on the same kernels. Measured refactorization, BLAS pinned to 1 thread: poisson2d_512 0.4781 -> 0.3921 s (-18%) poisson3d_32 0.3466 -> 0.3027 s (-13%) Residuals unchanged (1.5e-14 / 8.8e-16). GROUP=Core passes. Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com> Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
This was referenced Jul 25, 2026
ChrisRackauckas
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July 26, 2026 10:06
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Independent of #1109, #1111 and #1112; touches
src/SupernodalLU/numeric.jl(two hooks), the RecursiveFactorization extension, and 3 lines ofProject.toml.What
The supernodal factorization applies two BLAS-3 trsms per supernode against its just-factored diagonal block — the L21 panel on the right by U11, the U12 panel on the left by unit-L11. These now go through overridable hooks whose default is the stdlib triangular solve, with
LinearSolveRecursiveFactorizationExtoverriding them with TriangularSolve.Why this costs nothing
TriangularSolve is a hard dependency of RecursiveFactorization and is what RecursiveFactorization uses for its own trsms internally. It is declared here as a weakdep purely to trigger the extension; because RecursiveFactorization pulls it in transitively,
using RecursiveFactorizationalone still activates everything — no user gains an install. That is also exactly the condition under whichRFLUFactorizationbecomes the dense default, so the sparse solver's panel work and the dense default end up on the same kernels.(This recovers the gap I flagged when the diagonal-block factorization moved to LinearSolve's dense
init/solve!: that move was performance-neutral on its own, and the ~15 % that had been attributed to it was in fact the panel trsms.)Measured (refactorization, BLAS pinned to 1 thread)
Residuals unchanged (1.5e-14 / 8.8e-16). Verified the extension actually loads and takes the override path in an environment with RecursiveFactorization present.
GROUP=Corepasses.🤖 Generated with Claude Code
https://claude.ai/code/session_017rr42T1vFRRT8D7DMAmJzf