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Fix per-thread workspace overlap with user-supplied work[] (lwork > 0) - #1
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Port of xiaoyeli/superlu_mt#36 to the macro base file. When the caller supplies work[] (lwork > 0), each factorization thread allocates its private iwork/dwork from the TAIL of that stack in p@(pre)gstrf_WorkInit(), but p@(pre)gstrf_WorkFree() reset the whole TAIL (top2 = size) as soon as any one thread finished, releasing the work arrays of threads that were still running. A thread that started afterwards then got TAIL memory overlapping a live thread's marker[]/dense[] and overwrote them during its ifill()/@(pre)fill() initialization, producing spurious zero pivots (intermittent failures in p[cz]test_4_{10,19}_2_100000000_LA). Count the threads holding TAIL work arrays and reset the TAIL only when the last one frees its arrays. The added lines contain no precision macros, so the extracted p{s,d,c,z}memory.c match the files merged in superlu_mt exactly. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_017GsYX7J15S6uvtUoRMWYwi
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Summary
Port of xiaoyeli/superlu_mt#36 (merged) to the macro base file
trunk/SRC/pxmemory.base, so the fix is not lost the next time the precision-dependent sources are regenerated.Problem
When the caller supplies
work[](lwork > 0), each factorization thread allocates its privateiwork/dworkfrom the TAIL of that stack inp@(pre)gstrf_WorkInit(). Butp@(pre)gstrf_WorkFree()reset the whole TAIL (stack.top2 = stack.size) as soon as any one thread finished, releasing the work arrays of threads still running. A thread that started afterwards then got TAIL memory overlapping a live thread'smarker[]/dense[]and overwrote them during itsifill()/@(pre)fill()initialization. The result was spurious zero pivots: the intermittent failures inp[cz]test_4_{10,19}_2_100000000_LAreported in xiaoyeli/superlu_mt#34.Fix
p@(pre)gstrf_WorkInit()counts the threads holding TAIL work arrays (nwork_users), under the existing stack lock.p@(pre)gstrf_WorkFree()resets the TAIL only when that count drops to 0.p@(pre)gstrf_SetupSpace()and the refactorization path inp@(pre)gstrf_MemInit().Verification
The
extracttool is not available in my environment, so I did not regenerate the.cfiles here. Instead I compared the added/removed lines of this diff against the diffs of all four merged files (SRC/p{s,d,c,z}memory.cin superlu_mt commit2d564a6): they are identical in every case. The changed lines contain no precision macros, so extraction will produce exactly the files already merged in superlu_mt. Stress-test results for the fix itself are in xiaoyeli/superlu_mt#36.Only
trunk/is changed, per the README. The copy underSuperLU_MT_base-branch/SRC/pxmemory.baseis left as is.🤖 Generated with Claude Code
https://claude.ai/code/session_017GsYX7J15S6uvtUoRMWYwi
Generated by Claude Code