Restrict unrolling to loops that are nested within less than 4 loops #1595
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as unrolling and analyzing empty loops is cheaper than visiting loops for collecting the nr of the instructions
karoliineh
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sv-comp
sim642
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Oct 11, 2024
For reference, in SV-COMP 2024 we also had a bunch of fixpoint errors: https://sv-comp.sosy-lab.org/2024/results/results-verified/goblint.results.SV-COMP24.table.html#/table?filter=0(0*status*(status(in(ERROR%20%28verify%29)))). |
sim642
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Nov 28, 2024
CHANGES: Functionally equivalent to Goblint in SV-COMP 2025. * Add 32bit vs 64bit architecture support (goblint/analyzer#54, goblint/analyzer#1574). * Add per-function context gas analysis (goblint/analyzer#1569, goblint/analyzer#1570, goblint/analyzer#1598). * Adapt automatic static loop unrolling (goblint/analyzer#1516, goblint/analyzer#1582, goblint/analyzer#1583, goblint/analyzer#1584, goblint/analyzer#1590, goblint/analyzer#1595, goblint/analyzer#1599). * Adapt automatic configuration tuning (goblint/analyzer#1450, goblint/analyzer#1612, goblint/analyzer#1181, goblint/analyzer#1604). * Simplify non-relational integer invariants in witnesses (goblint/analyzer#1517). * Fix excessive hash collisions (goblint/analyzer#1594, goblint/analyzer#1602). * Clean up various code (goblint/analyzer#1095, goblint/analyzer#1523, goblint/analyzer#1554, goblint/analyzer#1575, goblint/analyzer#1588, goblint/analyzer#1597, goblint/analyzer#1614).
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This PR addresses the excessive resource usage introduced in bb6f9aa.
As the amount of unrolling grows exponentially with the number of nested loops, we determined what would be a reasonable amount of nestings with a 5s run on the sv-benchmarks and found that unrolling less than 4 loops is a reasonable metric.
On the downside, this PR introduces an issue where some termination tasks do not reach a fixpoint. Unfortunately, I was not able to trace it to the cause, but we made a quick run, and it seems to not impact our overall scores (compared to SV-COMP 2023, we lost 2 termination tasks, but we also currently run out of resources for these).
So, (hopefully) this PR fixes more things than it breaks. Edit: we made a run and, indeed, this PR does not break anything else but fixes the excessive resource usage with 717 tasks going from errors back to unknowns.