Fix DivideError in affine_transform for degenerate rational inputs#47
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Fix DivideError in affine_transform for degenerate rational inputs#47
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When the affine transformation has no valid integer mappings (e.g. when the denominator s is even and b_int has odd components while all entries of A_int are even), the carry set becomes empty, producing zero-sized tensors that cause a DivideError during reshape. Handle this by detecting empty carry sets after both the main loop and the open boundary extension loop, returning zero tensors with a warning. Fixes #46 Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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Summary
DivideErrorRoot Cause
When the common denominator
sis even andb_inthas odd components while all entries ofA_intare even, the constraintA*x + b + c ≡ 0 (mod 2)is never satisfied. This causesaffine_transform_coreto return an empty carry set, producing tensors with zero-sized dimensions. Subsequentreshape(tensor, 0, :)hits0 ÷ 0→DivideError.The transformation is mathematically degenerate — it maps no integer grid points to integer grid points. A warning is emitted to alert users.
Fixes #46
Test plan
degenerate_rational (issue #46)that reproduces the exact crash🤖 Generated with Claude Code