delta/go-git.git/src/math/bits, branch dev.debug

math/bits: add examples for leading zero methods

2017-07-15T21:55:58+00:00

Change-Id: Ib491d144387a7675af370f7b925fe6e62440d153
Reviewed-on: https://go-review.googlesource.com/48966
Run-TryBot: Kevin Burke 
TryBot-Result: Gobot Gobot 
Reviewed-by: Kevin Burke

cmd/compile: ppc64x intrinsics for math/bits

2017-05-10T12:10:56+00:00

This adds math/bits intrinsics for OnesCount, Len, TrailingZeros on
ppc64x.

benchmark                       old ns/op     new ns/op     delta
BenchmarkLeadingZeros-16        4.26          1.71          -59.86%
BenchmarkLeadingZeros16-16      3.04          1.83          -39.80%
BenchmarkLeadingZeros32-16      3.31          1.82          -45.02%
BenchmarkLeadingZeros64-16      3.69          1.71          -53.66%
BenchmarkTrailingZeros-16       2.55          1.62          -36.47%
BenchmarkTrailingZeros32-16     2.55          1.77          -30.59%
BenchmarkTrailingZeros64-16     2.78          1.62          -41.73%
BenchmarkOnesCount-16           3.19          0.93          -70.85%
BenchmarkOnesCount32-16         2.55          1.18          -53.73%
BenchmarkOnesCount64-16         3.22          0.93          -71.12%

Update #18616

I also made a change to bits_test.go because when debugging some failures
the output was not quite providing the right argument information.

Change-Id: Ia58d31d1777cf4582a4505f85b11a1202ca07d3e
Reviewed-on: https://go-review.googlesource.com/41630
Run-TryBot: Lynn Boger 
TryBot-Result: Gobot Gobot 
Reviewed-by: Carlos Eduardo Seo 
Reviewed-by: Keith Randall

math/bits: support negative rotation count and remove RotateRight

2017-04-11T23:57:24+00:00

For details see the discussion on the issue below.

RotateLeft functions can now be inlined because the don't panic
anymore for negative rotation counts.

name            old time/op  new time/op  delta
RotateLeft-8    6.72ns ± 2%  1.86ns ± 0%  -72.33%  (p=0.016 n=5+4)
RotateLeft8-8   4.41ns ± 2%  1.67ns ± 1%  -62.15%  (p=0.008 n=5+5)
RotateLeft16-8  4.46ns ± 6%  1.65ns ± 0%  -63.06%  (p=0.008 n=5+5)
RotateLeft32-8  4.50ns ± 5%  1.67ns ± 1%  -62.86%  (p=0.008 n=5+5)
RotateLeft64-8  4.54ns ± 1%  1.85ns ± 1%  -59.32%  (p=0.008 n=5+5)

https://perf.golang.org/search?q=upload:20170411.4

(Measured on 2.3 GHz Intel Core i7 running macOS 10.12.3.)

For #18616.

Change-Id: I0828d80d54ec24f8d44954a57b3d6aeedb69c686
Reviewed-on: https://go-review.googlesource.com/40394
Reviewed-by: Brad Fitzpatrick

math/bits: move left-over functionality from bits_impl.go to bits.go

2017-02-28T23:50:47+00:00

Removes an extra function call for TrailingZeroes and thus may
increase chances for inlining.

Change-Id: Iefd8d4402dc89b64baf4e5c865eb3dadade623af
Reviewed-on: https://go-review.googlesource.com/37613
Run-TryBot: Robert Griesemer 
Reviewed-by: Brad Fitzpatrick

math/bits: faster LeadingZeros and Len functions

2017-02-28T20:55:13+00:00

benchmark                     old ns/op     new ns/op     delta
BenchmarkLeadingZeros-8       8.43          3.10          -63.23%
BenchmarkLeadingZeros8-8      8.13          1.33          -83.64%
BenchmarkLeadingZeros16-8     7.34          2.07          -71.80%
BenchmarkLeadingZeros32-8     7.99          2.87          -64.08%
BenchmarkLeadingZeros64-8     8.13          2.96          -63.59%

Measured on 2.3 GHz Intel Core i7 running macOS 10.12.3.

Change-Id: Id343531b408d42ac45f10c76f60e85bdb977f91e
Reviewed-on: https://go-review.googlesource.com/37582
Reviewed-by: Brad Fitzpatrick

math/bits: faster TrailingZeroes8

2017-02-28T20:55:01+00:00

For sizes > 8, the existing code is faster.

benchmark                     old ns/op     new ns/op     delta
BenchmarkTrailingZeros8-8     1.95          1.29          -33.85%

Measured on 2.3 GHz Intel Core i7 running macOS 10.12.3.

Change-Id: I6f3a33ec633a2c544ec29693c141f2f99335c745
Reviewed-on: https://go-review.googlesource.com/37581
Reviewed-by: Brad Fitzpatrick

math/bits: faster OnesCount using table lookups for sizes 8,16,32

2017-02-28T20:54:49+00:00

For uint64, the existing algorithm is faster.

benchmark                  old ns/op     new ns/op     delta
BenchmarkOnesCount8-8      1.95          0.97          -50.26%
BenchmarkOnesCount16-8     2.54          1.39          -45.28%
BenchmarkOnesCount32-8     2.61          1.96          -24.90%

Measured on 2.3 GHz Intel Core i7 running macOS 10.12.3.

Change-Id: I6cc42882fef3d24694720464039161e339a9ae99
Reviewed-on: https://go-review.googlesource.com/37580
Reviewed-by: Brad Fitzpatrick

math/bits: faster Reverse8/16 functions using table lookups

2017-02-25T22:18:58+00:00

Measured on 2.3 GHz Intel Core i7, running macOS 10.12.3:

benchmark                old ns/op     new ns/op     delta
BenchmarkReverse8-8      1.70          0.99          -41.76%
BenchmarkReverse16-8     2.24          1.32          -41.07%

Fixes #19279.

Change-Id: I398cf8a3513b7fa63c130efc7846a7c5353999d4
Reviewed-on: https://go-review.googlesource.com/37459
Run-TryBot: Robert Griesemer 
TryBot-Result: Gobot Gobot 
Reviewed-by: Brad Fitzpatrick

math/bits: fix incorrect doc strings for TrailingZeros functions

2017-02-25T00:58:25+00:00

Change-Id: I3e40018ab1903d3b9ada7ad7812ba71ea2a428e7
Reviewed-on: https://go-review.googlesource.com/37456
Reviewed-by: Brad Fitzpatrick

math/bits: faster OnesCount

2017-02-19T18:50:48+00:00

Using some additional suggestions per "Hacker's Delight".
Added documentation and extra tests.

Measured on 1.7 GHz Intel Core i7, running macOS 10.12.3.

benchmark                  old ns/op     new ns/op     delta
BenchmarkOnesCount-4       7.34          5.38          -26.70%
BenchmarkOnesCount8-4      2.03          1.98          -2.46%
BenchmarkOnesCount16-4     2.56          2.50          -2.34%
BenchmarkOnesCount32-4     2.98          2.39          -19.80%
BenchmarkOnesCount64-4     4.22          2.96          -29.86%

Change-Id: I566b0ef766e55cf5776b1662b6016024ebe5d878
Reviewed-on: https://go-review.googlesource.com/37223
Reviewed-by: Matthew Dempsky 
Run-TryBot: Matthew Dempsky 
TryBot-Result: Gobot Gobot