runtime: use integer math for hashmap overLoadFactor
Change-Id: I92cf39a05e738a03d956779d7a1ab1ef8074b2ab
Reviewed-on: https://go-review.googlesource.com/54655
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
diff --git a/src/runtime/hashmap.go b/src/runtime/hashmap.go
index 87d0d26..64ec844 100644
--- a/src/runtime/hashmap.go
+++ b/src/runtime/hashmap.go
@@ -64,8 +64,10 @@
bucketCntBits = 3
bucketCnt = 1 << bucketCntBits
- // Maximum average load of a bucket that triggers growth.
- loadFactor = 6.5
+ // Maximum average load of a bucket that triggers growth is 6.5.
+ // Represent as loadFactorNum/loadFactDen, to allow integer math.
+ loadFactorNum = 13
+ loadFactorDen = 2
// Maximum key or value size to keep inline (instead of mallocing per element).
// Must fit in a uint8.
@@ -984,8 +986,7 @@
// overLoadFactor reports whether count items placed in 1<<B buckets is over loadFactor.
func overLoadFactor(count int64, B uint8) bool {
- // TODO: rewrite to use integer math and comparison?
- return count >= bucketCnt && float32(count) >= loadFactor*float32((uint64(1)<<B))
+ return count >= bucketCnt && uint64(count) >= loadFactorNum*((uint64(1)<<B)/loadFactorDen)
}
// tooManyOverflowBuckets reports whether noverflow buckets is too many for a map with 1<<B buckets.
diff --git a/src/runtime/stubs.go b/src/runtime/stubs.go
index ce9b67a..7f504e6 100644
--- a/src/runtime/stubs.go
+++ b/src/runtime/stubs.go
@@ -91,7 +91,7 @@
}
// exported value for testing
-var hashLoad = loadFactor
+var hashLoad = float32(loadFactorNum) / float32(loadFactorDen)
//go:nosplit
func fastrand() uint32 {
