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[3.14] gh-142145: Avoid timing measurements in quadratic behavior test (gh-143105)#143139

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Merged
colesbury merged 1 commit into from
Dec 24, 2025
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[3.14] gh-142145: Avoid timing measurements in quadratic behavior test (gh-143105) #143139

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48 changes: 30 additions & 18 deletions Lib/test/test_minidom.py
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Original file line numberDiff line numberDiff line change
Expand Up@@ -2,7 +2,6 @@

importcopy
importpickle
importtime
importio
fromtestimportsupport
importunittest
Expand DownExpand Up@@ -178,23 +177,36 @@ def testAppendChild(self):
deftestAppendChildNoQuadraticComplexity(self):
impl=getDOMImplementation()

newdoc=impl.createDocument(None, "some_tag", None)
top_element=newdoc.documentElement
children= [newdoc.createElement(f"child-{i}") foriinrange(1, 2**15+1)]
element=top_element

start=time.monotonic()
forchildinchildren:
element.appendChild(child)
element=child
end=time.monotonic()

# This example used to take at least 30 seconds.
# Conservative assertion due to the wide variety of systems and
# build configs timing based tests wind up run under.
# A --with-address-sanitizer --with-pydebug build on a rpi5 still
# completes this loop in <0.5 seconds.
self.assertLess(end-start, 4)
defwork(n):
doc=impl.createDocument(None, "some_tag", None)
element=doc.documentElement
total_calls=0

# Count attribute accesses as a proxy for work done
defgetattribute_counter(self, attr):
nonlocaltotal_calls
total_calls+=1
returnobject.__getattribute__(self, attr)

withsupport.swap_attr(Element, "__getattribute__", getattribute_counter):
for_inrange(n):
child=doc.createElement("child")
element.appendChild(child)
element=child
returntotal_calls

# Doubling N should not ~quadruple the work.
w1=work(1024)
w2=work(2048)
w3=work(4096)

self.assertGreater(w1, 0)
r1=w2/w1
r2=w3/w2
self.assertLess(
max(r1, r2), 3.2,
msg=f"Possible quadratic behavior: work={w1,w2,w3} ratios={r1,r2}"
)

deftestSetAttributeNodeWithoutOwnerDocument(self):
# regression test for gh-142754
Expand Down
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