Improve BDD sifting (2x speed, more reduction) #2890
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- Add AdaptiveEffort to dynamically adjust optimization parameters based on observed improvement rates (increase effort when making progress, decrease when plateauing) - Add block moves optimization that moves groups of dependent conditions together to escape local minima - Add cost-based tie-breaking using BddCostEstimator when multiple positions have the same node count
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kstich
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Dec 19, 2025
...s-engine/src/main/java/software/amazon/smithy/rulesengine/logic/bdd/SiftingOptimization.java
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...s-engine/src/main/java/software/amazon/smithy/rulesengine/logic/bdd/SiftingOptimization.java
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JordonPhillips
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Dec 19, 2025
This commit adds a new function to the rules engine, ite, that performs
an if-then-else check on a boolean expression without branching. By not
needing to branch in the decision tree, we avoid SSA transforms on
divergent branches which would create syntactically different but
semantically identical expressions that the BDD cannot deduplicate.
This commit also adds an S3-specific decision tree transform that
canonicalizes S3Express rules for better BDD compilation:
1. AZ extraction: Rewrites position-dependent substring operations to
use a single split(Bucket, "--")[1] expression across all branches
2. URL canonicalization: Uses ITE to compute FIPS/DualStack URL segments,
collapsing 4 URL variants into a single template with {_s3e_fips} and
{_s3e_ds} placeholders
3. Auth scheme canonicalization: Uses ITE to select sigv4 vs
sigv4-s3express based on DisableS3ExpressSessionAuth
The transform makes the rules tree ~30% larger but enables dramatic BDD
compression by making URL templates identical across FIPS/DualStack/auth
variants. Endpoints that previously appeared distinct now collapse into
single BDD results, reducing nodes and results by ~43%.
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