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Avoid quadratic behaviour in _unify_attribute (#2673)

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ARTIQ maintains a list of all known instances of a particular class, and
after each attribute access, `_unify_attribute` is called to check all
these instances have this attribute (and it's the right type).

While the attribute type computation is cached, this is still O(nm)
(with n being the number of instances, and m the number of attribute
lookups). For something like ndscan's `FloatParamHandle.get`, you can
have a lot of both.

This commit changes `_unify_attribute` to only check the attributes of
new instances, effectively lowering the complexity to O(n). This
provides a small (5%) boost to compile times.

Signed-off-by: Jonathan Coates <jonathan.coates@oxionics.com>
This commit is contained in:
Jonathan Coates 2025-02-07 00:33:08 +00:00 committed by GitHub
parent ae12270363
commit c8d0ab9afe
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1 changed files with 30 additions and 3 deletions
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33
artiq/compiler/embedding.py
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@ -274,6 +274,27 @@ class EmbeddingMap:
))
class _ValueInfo:
"""
A collection of all values of a particular type.
Attributes:
:attr:`objects`: A list of all objects and the location they were added from.
:attr:`unchecked_attributes`: The known attributes for this type, and a list of
values where we have not yet checked the attribute's presence.
"""
def __init__(self):
self.objects: list[tuple[object, source.Range]] = []
self.unchecked_attributes: dict[str, list[tuple[object, source.Range]]] = {}
def append(self, val_and_loc):
self.objects.append(val_and_loc)
for attr_store in self.unchecked_attributes.values():
attr_store.append(val_and_loc)
class ASTSynthesizer:
def __init__(self, embedding_map, value_map, quote_function=None, expanded_from=None):
self.source = ""
@ -807,7 +828,13 @@ class StitchingInferencer(Inferencer):
# that we can successfully serialize the value of the attribute we
# are now adding at the code generation stage.
object_type = value_node.type.find()
for object_value, object_loc in self.value_map[object_type]:
values: _ValueInfo = self.value_map[object_type]
# Take all objects whose attribute we haven't checked yet.
attribute_objects = values.unchecked_attributes.get(attr_name, values.objects)
values.unchecked_attributes[attr_name] = []
for object_value, object_loc in attribute_objects:
attr_type_key = (id(object_value), attr_name)
try:
attributes, attr_value_type = self.attr_type_cache[attr_type_key]
@ -888,7 +915,7 @@ class Stitcher:
self.functions = {}
self.embedding_map = EmbeddingMap(old_embedding_map)
self.value_map = defaultdict(lambda: [])
self.value_map = defaultdict(_ValueInfo)
self.definitely_changed = False
self.destination = destination
@ -946,7 +973,7 @@ class Stitcher:
# value is guaranteed to have it too.
continue
for value, loc in self.value_map[instance_type]:
for value, loc in self.value_map[instance_type].objects:
if hasattr(value, attribute):
continue