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runtime: hash collisions in arm64 #33960

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randall77 opened this issue Aug 29, 2019 · 1 comment
Closed

runtime: hash collisions in arm64 #33960

randall77 opened this issue Aug 29, 2019 · 1 comment

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@randall77
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@randall77 randall77 commented Aug 29, 2019

The arm64 builder is failing on a hash function tests I just checked in. I think the assembly code is using only the low 32 bits of the seed. The test that makes this evident is:

--- FAIL: TestSmhasherSeed (0.13s)
    smhasher_test.go:94: unexpected number of collisions: got=100000 mean=0.000000 stddev=0.000033
FAIL
FAIL	bytes/hash	0.319s

aeshashbody does:

	VMOV	R3, V30.S[0]
	VMOV	R1, V30.S[1] // load length into seed

We should really use VMOVD into V30.D[0] and V30.D[1], I think.

@mengzhuo @cherryyz

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@gopherbot gopherbot commented Aug 29, 2019

Change https://golang.org/cl/192498 mentions this issue: runtime: use all 64 bits of hash seed on arm64

@gopherbot gopherbot closed this in f484e96 Aug 30, 2019
tomocy added a commit to tomocy/go that referenced this issue Sep 1, 2019
Fixes golang#33960

Change-Id: I4f8cf65dcf4140a97e7b368572b31c171c453316
Reviewed-on: https://go-review.googlesource.com/c/go/+/192498
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
t4n6a1ka added a commit to t4n6a1ka/go that referenced this issue Sep 5, 2019
Fixes golang#33960

Change-Id: I4f8cf65dcf4140a97e7b368572b31c171c453316
Reviewed-on: https://go-review.googlesource.com/c/go/+/192498
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
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