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Fix #1619: Reduce collision rate in NameTable #3768

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Merged
merged 1 commit into from
Apr 9, 2018
Merged

Fix #1619: Reduce collision rate in NameTable #3768

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16 changes: 9 additions & 7 deletions compiler/src/dotty/tools/dotc/core/Names.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -546,13 +546,15 @@ object Names {
private[this] var size = 1

/** The hash of a name made of from characters cs[offset..offset+len-1]. */
private def hashValue(cs: Array[Char], offset: Int, len: Int): Int =
if (len > 0)
(len * (41 * 41 * 41) +
cs(offset) * (41 * 41) +
cs(offset + len - 1) * 41 +
cs(offset + (len >> 1)))
else 0
private def hashValue(cs: Array[Char], offset: Int, len: Int): Int = {
var i = offset
var hash = 0
while (i < len + offset) {
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Compute len+offset only once.

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Pretty sure the jvm should figure it out :).

hash = 31 * hash + cs(i)
i += 1
}
hash
}

/** Is (the ASCII representation of) name at given index equal to
* cs[offset..offset+len-1]?
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