Compile-time check for zero alpha in matmul #1293
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jishnub
commented
Apr 18, 2025
Codecov ReportAttention: Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## master #1293 +/- ##
==========================================
- Coverage 92.03% 92.03% -0.01%
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Files 34 34
Lines 15501 15503 +2
==========================================
+ Hits 14267 14268 +1
- Misses 1234 1235 +1 ☔ View full report in Codecov by Sentry. 🚀 New features to boost your workflow:
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Does this improve TTFX visibly? |
dkarrasch
approved these changes
Apr 18, 2025
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It helps a bit when the branch calls julia> n = 4; T = t = Bidiagonal(ones(n), ones(n-1), :U); C = similar(T); D = Diagonal(T);
julia> @time mul!(C, T, D);
0.124931 seconds (398.97 k allocations: 20.078 MiB, 99.98% compilation time) # master
0.110213 seconds (387.34 k allocations: 19.559 MiB, 99.98% compilation time) # this PROften, the different would be small, as the branch is trivial. |
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Currently, we check for
iszero(_add.alpha)in various matrix multiplication functions, where_add::MulAddMul. However, aMulAddMul(alpha, beta)storesisone(alpha)as a type parameter, and ifalphais one, we know at compile-time thatiszero(_add.alpha)isfalse. Using the type parameter in dispatch would allow us to eliminate theiszero(alpha)branches.