[PERF]: Use a list for lookup in contiguous FastEnums

Our FastEnum implementation (and our usage of stdlib.enum.IntEnum before that) uses a dictionary from integers to a singleton enum value to return an enum from C (which is a simple int) to Python (which is a value/name pair of a specific type).

For enums where all of the values are contiguous starting at zero, (which we could determine at code-generation time) we could instead use a list for this mapping which would provide O(1) lookup.

For enums where all of the values are contiguous starting at zero

We'll need to ensure the codegen checks for this. In many cases library teams like to leave holes lol

For enums where all of the values are contiguous starting at zero

We'll need to ensure the codegen checks for this. In many cases library teams like to leave holes lol

Oh, yes, indeed. Many are contiguous, but a lot of them aren't. And a lot are "bit flags", too.

No measurable improvement with this change, so closing.

enum from int: Mean +- std dev: [baseline] 167 ns +- 7 ns -> [contiguous] 178 ns +- 9 ns: 1.06x slower
enum value: Mean +- std dev: [baseline] 80.1 ns +- 3.8 ns -> [contiguous] 81.7 ns +- 2.7 ns: 1.02x slower
cuda.bindings.runtime import: Mean +- std dev: [baseline] 63.6 ms +- 1.3 ms -> [contiguous] 62.4 ms +- 1.2 ms: 1.02x faster
cuda.bindings.nvrtc import: Mean +- std dev: [baseline] 56.3 ms +- 1.7 ms -> [contiguous] 55.1 ms +- 1.3 ms: 1.02x faster

Benchmark hidden because not significant (3): int from enum, isinstance(enum, IntEnum), cuda.bindings.driver import

Geometric mean: 1.01x slower

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[PERF]: Use a list for lookup in contiguous `FastEnum`s #1637

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[PERF]: Use a list for lookup in contiguous FastEnums #1637

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leofang commented on Feb 18, 2026

mdboom commented on Feb 19, 2026

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[PERF]: Use a list for lookup in contiguous `FastEnum`s #1637