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Tests: Introduce a HashTable benchmark for "table thrashing"

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Thrashing is what I call the situations where a table is mostly filled
with deleted markers, causing an increase in size (at least temporarily)
when a simple re-hash would be enough to get rid of those. This happens
when a hash table (especially with many elements) has a lot of deletes
and re-inserts done to it, which is what this benchmark does.
This commit is contained in:
kleines Filmröllchen 2022-03-07 22:24:15 +01:00 • committed by Andreas Kling
parent bcb8937898
commit e73e579446
1 changed files with 18 additions and 0 deletions
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18
Tests/AK/TestHashTable.cpp
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@ -234,3 +234,21 @@ TEST_CASE(capacity_leak)
}
EXPECT(table.capacity() < 100u);
}
// Inserting and removing a bunch of elements will "thrash" the table, leading to a lot of "deleted" markers.
BENCHMARK_CASE(benchmark_thrashing)
{
HashTable<int> table;
// Ensure that there needs to be some copying when rehashing.
table.set(3);
table.set(7);
table.set(11);
table.set(13);
for (int i = 0; i < 10'000; ++i) {
table.set(-i);
}
for (int i = 0; i < 10'000'000; ++i) {
table.set(i);
table.remove(i);
}
}