Cache Qid instances for common types #6371
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Codecov ReportAll modified and coverable lines are covered by tests ✅
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Coverage 97.80% 97.81%
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I don't know of anything to do this automatically. Which is unfortunate because it seems like a rather natural thing to do, and in fact I think we could improve performance by doing this for other heavily-used cirq classes as well.
We could do that, though I suspect it's not common to create so many different qubits that this would matter. |
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Changed to use a WeakValueDictionary for caching. |
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| @@ -178,22 +171,33 @@ class GridQid(_BaseGridQid): | |||
| cirq.GridQid(5, 4, dimension=2) | |||
| """ | |||
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| def __init__(self, row: int, col: int, *, dimension: int) -> None: | |||
| """Initializes a grid qid at the given row, col coordinate | |||
| _cache = weakref.WeakValueDictionary[Tuple[int, int, int], 'cirq.GridQid']() | |||
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A line comment explaining this would be appreciated.
| cls._cache[key] = inst | ||
| return inst | ||
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| def __getnewargs_ex__(self): |
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This seems like a pretty obscure dunder function. Maybe a docstring to explain what this is would be helpful.
Here we add caches of common qubit types
GridQubit,LineQubit, andNamedQubit(and their associatedQidtypes) so that we can reuse instances of these objects. Operations on these objects are extremely common, so reusing instances can have significant performance benefits, in particular because hashes do not need to be recomputed and equality comparisons can be short-circuited with instance equality in common cases.