Relax non-negative-integer Pow to ipow (fix symbolic-exponent codegen)#2426
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ThrudPrimrose wants to merge 4 commits into
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Relax non-negative-integer Pow to ipow (fix symbolic-exponent codegen)#2426ThrudPrimrose wants to merge 4 commits into
ThrudPrimrose wants to merge 4 commits into
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DaCe's symbolic C++ printer emits dace::math::pow (libm, double) for a non-constant exponent, which is illegal where a C++ integer is required -- an array size, a subscript, or a loop bound. For example the radix decomposition R**(K-i-1) used as a stride in stockham_fft fails to compile. dace::math::ipow (repeated multiply, exact integer) is the correct lowering iff the exponent is a non-negative integer (its C++ exponent is unsigned, so a negative one is catastrophic). - Add an ipow SymPy Function (dace/symbolic.py) lowering to dace::math::ipow; registered so it round-trips through parsing and serialization. - Add the RelaxIntegerPowers pass rewriting Pow -> ipow for non-negative integer exponents: constants, integer-valued float literals, and symbolic exponents proven >= 0 by interval analysis over the enclosing loop / map iterator ranges. A scoped recursive descent binds each iterator (and each SDFG's declared symbol signs) as it enters loops, maps and nested SDFGs and drops them on exit; the proof reuses equalize_symbol and the assuming/ask idiom. Wired last in SIMPLIFY_PASSES. - Teach infer_symbols_from_datadescriptor to read ipow as Pow when solving a shape for its symbols (ipow is opaque to the solver otherwise). - Unskip the stockham_fft CPU test; add tests/passes/relax_integer_powers_test.py.
_SerializedSymbolicParser._functions (the serialize_symbolic/
deserialize_symbolic path used for SDFG properties like an Array's
total_size) lacked ipow, so a serialized 64*ipow(P, 2) deserialized to an
opaque Function('ipow') that never folds; int(evaluate(total_size, {P: n}))
then raised "Cannot convert symbols to int" (mpi subarrays_test BlockGather,
whose return shape is 8*P x 8*P). Register the real class so it round-trips
and folds.
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Here I provide a pass relaxes
powtoipowif the exponent is nonnegative. It analyzes loop ranges / map ranges to check the bound of the expression, as appearing in stockham_fft. This way, we can compile stockham_fft.