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perf: Avoid redundant array indexing math in ArenaDictionary probing loop #80

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Merged
myarichuk merged 1 commit into from
Jun 20, 2026
Merged

perf: Avoid redundant array indexing math in ArenaDictionary probing loop #80

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78 changes: 39 additions & 39 deletions src/SharpArena/Collections/ArenaDictionary.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -86,10 +86,10 @@ private readonly int FindBucket(TKey key)

while (true)
{
int entryIdxPlusOne = buckets[index];
if (entryIdxPlusOne == 0) return (int)index;
int entryIdx = buckets[index] - 1;
if (entryIdx < 0) return (int)index;

if (keys[entryIdxPlusOne - 1].Equals(key)) return (int)index;
if (keys[entryIdx].Equals(key)) return (int)index;

index = (index + 1) & mask;
}
Expand Down Expand Up @@ -167,8 +167,8 @@ public bool TryAdd(TKey key, TValue value)
}

int bucketIdx = FindBucket(key);
int entryIdxPlusOne = _header->Buckets[bucketIdx];
if (entryIdxPlusOne != 0) return false;
int entryIdx = _header->Buckets[bucketIdx] - 1;
if (entryIdx >= 0) return false;

int newEntryIdx = _header->Count++;
_header->Buckets[bucketIdx] = newEntryIdx + 1;
Expand All @@ -186,8 +186,8 @@ private void AddOrUpdate(TKey key, TValue value)
}

int bucketIdx = FindBucket(key);
int entryIdxPlusOne = _header->Buckets[bucketIdx];
if (entryIdxPlusOne == 0)
int entryIdx = _header->Buckets[bucketIdx] - 1;
if (entryIdx < 0)
{
int newEntryIdx = _header->Count++;
_header->Buckets[bucketIdx] = newEntryIdx + 1;
Expand All @@ -196,7 +196,7 @@ private void AddOrUpdate(TKey key, TValue value)
}
else
{
((TValue*)_header->Values)[entryIdxPlusOne - 1] = value;
((TValue*)_header->Values)[entryIdx] = value;
}
}

Expand Down Expand Up @@ -264,9 +264,9 @@ public readonly bool ContainsKey(ReadOnlySpan<char> key)

while (true)
{
int entryIdxPlusOne = buckets[index];
if (entryIdxPlusOne == 0) return false;
if (keys[entryIdxPlusOne - 1].Equals(key)) return true;
int entryIdx = buckets[index] - 1;
if (entryIdx < 0) return false;
if (keys[entryIdx].Equals(key)) return true;
index = (index + 1) & mask;
}
}
Expand All @@ -290,9 +290,9 @@ public readonly bool ContainsKey(ReadOnlySpan<char> key)
uint index = hash & mask;
while (true)
{
int entryIdxPlusOne = buckets[index];
if (entryIdxPlusOne == 0) return false;
if (keys[entryIdxPlusOne - 1].Equals(byteKey)) return true;
int entryIdx = buckets[index] - 1;
if (entryIdx < 0) return false;
if (keys[entryIdx].Equals(byteKey)) return true;
index = (index + 1) & mask;
}
}
Expand Down Expand Up @@ -323,9 +323,9 @@ public readonly bool ContainsKey(ReadOnlySpan<byte> key)
uint index = hash & mask;
while (true)
{
int entryIdxPlusOne = buckets[index];
if (entryIdxPlusOne == 0) return false;
if (keys[entryIdxPlusOne - 1].Equals(key)) return true;
int entryIdx = buckets[index] - 1;
if (entryIdx < 0) return false;
if (keys[entryIdx].Equals(key)) return true;
index = (index + 1) & mask;
}
}
Expand All @@ -350,9 +350,9 @@ public readonly bool ContainsKey(ReadOnlySpan<byte> key)

while (true)
{
int entryIdxPlusOne = buckets[index];
if (entryIdxPlusOne == 0) return false;
if (keys[entryIdxPlusOne - 1].Equals(charKey)) return true;
int entryIdx = buckets[index] - 1;
if (entryIdx < 0) return false;
if (keys[entryIdx].Equals(charKey)) return true;
index = (index + 1) & mask;
}
}
Expand All @@ -375,10 +375,10 @@ public readonly bool TryGetValue(TKey key, out TValue value)
{
CheckAlive();
int bucketIdx = FindBucket(key);
int entryIdxPlusOne = _header->Buckets[bucketIdx];
if (entryIdxPlusOne != 0)
int entryIdx = _header->Buckets[bucketIdx] - 1;
if (entryIdx >= 0)
{
value = ((TValue*)_header->Values)[entryIdxPlusOne - 1];
value = ((TValue*)_header->Values)[entryIdx];
return true;
}
value = default;
Expand Down Expand Up @@ -408,11 +408,11 @@ public readonly bool TryGetValue(ReadOnlySpan<char> key, out TValue value)

while (true)
{
int entryIdxPlusOne = buckets[index];
if (entryIdxPlusOne == 0) break;
if (keys[entryIdxPlusOne - 1].Equals(key))
int entryIdx = buckets[index] - 1;
if (entryIdx < 0) break;
if (keys[entryIdx].Equals(key))
{
value = values[entryIdxPlusOne - 1];
value = values[entryIdx];
return true;
}
index = (index + 1) & mask;
Expand All @@ -439,11 +439,11 @@ public readonly bool TryGetValue(ReadOnlySpan<char> key, out TValue value)
uint index = hash & mask;
while (true)
{
int entryIdxPlusOne = buckets[index];
if (entryIdxPlusOne == 0) break;
if (keys[entryIdxPlusOne - 1].Equals(byteKey))
int entryIdx = buckets[index] - 1;
if (entryIdx < 0) break;
if (keys[entryIdx].Equals(byteKey))
{
value = values[entryIdxPlusOne - 1];
value = values[entryIdx];
return true;
}
index = (index + 1) & mask;
Expand Down Expand Up @@ -479,11 +479,11 @@ public readonly bool TryGetValue(ReadOnlySpan<byte> key, out TValue value)
uint index = hash & mask;
while (true)
{
int entryIdxPlusOne = buckets[index];
if (entryIdxPlusOne == 0) break;
if (keys[entryIdxPlusOne - 1].Equals(key))
int entryIdx = buckets[index] - 1;
if (entryIdx < 0) break;
if (keys[entryIdx].Equals(key))
{
value = values[entryIdxPlusOne - 1];
value = values[entryIdx];
return true;
}
index = (index + 1) & mask;
Expand Down Expand Up @@ -511,11 +511,11 @@ public readonly bool TryGetValue(ReadOnlySpan<byte> key, out TValue value)

while (true)
{
int entryIdxPlusOne = buckets[index];
if (entryIdxPlusOne == 0) break;
if (keys[entryIdxPlusOne - 1].Equals(charKey))
int entryIdx = buckets[index] - 1;
if (entryIdx < 0) break;
if (keys[entryIdx].Equals(charKey))
{
value = values[entryIdxPlusOne - 1];
value = values[entryIdx];
return true;
}
index = (index + 1) & mask;
Expand Down
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