rust: peek_mut optim for lazy ancestors
This is one of the two optimizations that are also
present in the Python code: replacing pairs of pop/push
on the BinaryHeap by single updates, hence having it
under the hood maintain its consistency (sift) only once.
On Mozilla central, the measured gain (see details below)
is around 7%.
Creating the PeekMut object by calling peek_mut() right away
instead of peek() first is less efficient (gain is only 4%, stats
not included).
Our interpretation is that its creation has a cost which is vasted
in the cases where it ends by droping the value (Peekmut::pop()
just does self.heap.pop() anyway). On the other hand, the immutable
peek() is very fast: it's just taking a reference in the
underlying vector.
The Python version still has another optimization:
if parent(current) == current-1, then the heap doesn't need
to maintain its consistency, since we already know that
it's bigger than all the others in the heap.
Rust's BinaryHeap doesn't allow us to mutate its biggest
element with no housekeeping, but we tried it anyway, with a
copy of the BinaryHeap implementation with a dedicaded added
method: it's not worth the technical debt in our opinion
(we measured only a further 1.6% improvement).
One possible explanation would be that the sift is really fast
anyway in that case, whereas it's not in the case of Python,
because it's at least partly done in slow Python code.
Still it's possible that replacing BinaryHeap by something more
dedicated to discrete ordered types could be faster.
Measurements on mozilla-central:
Three runs of 'hg perfancestors' on the parent changeset:
Moyenne des médianes: 0.100587
! wall 0.100062 comb 0.100000 user 0.100000 sys 0.000000 (best of 98)
! wall 0.135804 comb 0.130000 user 0.130000 sys 0.000000 (max of 98)
! wall 0.102864 comb 0.102755 user 0.099286 sys 0.003469 (avg of 98)
! wall 0.101486 comb 0.110000 user 0.110000 sys 0.000000 (median of 98)
! wall 0.096804 comb 0.090000 user 0.090000 sys 0.000000 (best of 100)
! wall 0.132235 comb 0.130000 user 0.120000 sys 0.010000 (max of 100)
! wall 0.100258 comb 0.100300 user 0.096000 sys 0.004300 (avg of 100)
! wall 0.098384 comb 0.100000 user 0.100000 sys 0.000000 (median of 100)
! wall 0.099925 comb 0.100000 user 0.100000 sys 0.000000 (best of 98)
! wall 0.133518 comb 0.140000 user 0.130000 sys 0.010000 (max of 98)
! wall 0.102381 comb 0.102449 user 0.098265 sys 0.004184 (avg of 98)
! wall 0.101891 comb 0.090000 user 0.090000 sys 0.000000 (median of 98)
Mean of the medians: 0.100587
On the present changeset:
! wall 0.091344 comb 0.090000 user 0.090000 sys 0.000000 (best of 100)
! wall 0.122728 comb 0.120000 user 0.110000 sys 0.010000 (max of 100)
! wall 0.093268 comb 0.093300 user 0.089300 sys 0.004000 (avg of 100)
! wall 0.092567 comb 0.100000 user 0.090000 sys 0.010000 (median of 100)
! wall 0.093294 comb 0.080000 user 0.080000 sys 0.000000 (best of 100)
! wall 0.144887 comb 0.150000 user 0.140000 sys 0.010000 (max of 100)
! wall 0.097708 comb 0.097700 user 0.093400 sys 0.004300 (avg of 100)
! wall 0.094980 comb 0.100000 user 0.090000 sys 0.010000 (median of 100)
! wall 0.091262 comb 0.090000 user 0.080000 sys 0.010000 (best of 100)
! wall 0.123772 comb 0.130000 user 0.120000 sys 0.010000 (max of 100)
! wall 0.093188 comb 0.093200 user 0.089300 sys 0.003900 (avg of 100)
! wall 0.092364 comb 0.100000 user 0.090000 sys 0.010000 (median of 100)
Mean of the medians is 0.0933
Differential Revision: https://phab.mercurial-scm.org/D5358
$ branchcache=.hg/cache/branch2
$ listbranchcaches() {
> for f in .hg/cache/branch2*;
> do echo === $f ===;
> cat $f;
> done;
> }
$ purgebranchcaches() {
> rm .hg/cache/branch2*
> }
$ hg init t
$ cd t
$ hg branches
$ echo foo > a
$ hg add a
$ hg ci -m "initial"
$ hg branch foo
marked working directory as branch foo
(branches are permanent and global, did you want a bookmark?)
$ hg branch
foo
$ hg ci -m "add branch name"
$ hg branch bar
marked working directory as branch bar
$ hg ci -m "change branch name"
Branch shadowing:
$ hg branch default
abort: a branch of the same name already exists
(use 'hg update' to switch to it)
[255]
$ hg branch -f default
marked working directory as branch default
$ hg ci -m "clear branch name"
created new head
There should be only one default branch head
$ hg heads .
changeset: 3:1c28f494dae6
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: clear branch name
Merging and branches
$ hg co foo
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg branch
foo
set existing branch name fails unless force - setting existing parent branch works without force:
$ hg branch bar
abort: a branch of the same name already exists
(use 'hg update' to switch to it)
[255]
$ hg branch -f bar
marked working directory as branch bar
$ hg branch foo
marked working directory as branch foo
$ echo bleah > a
$ hg ci -m "modify a branch"
$ hg merge default
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg branch
foo
set existing branch name where branch head is ancestor:
$ hg branch bar
abort: a branch of the same name already exists
(use 'hg update' to switch to it)
[255]
set (other) parent branch as branch name
$ hg branch default
marked working directory as branch default
set (first) parent branch as branch name
$ hg branch foo
marked working directory as branch foo
$ hg ci -m "merge"
$ hg log -G -T '{rev}:{node|short} {branch} {desc}\n'
@ 5:530046499edf foo merge
|\
| o 4:adf1a74a7f7b foo modify a branch
| |
o | 3:1c28f494dae6 default clear branch name
| |
o | 2:c21617b13b22 bar change branch name
|/
o 1:6c0e42da283a foo add branch name
|
o 0:db01e8ea3388 default initial
$ hg branches
foo 5:530046499edf
default 3:1c28f494dae6 (inactive)
bar 2:c21617b13b22 (inactive)
$ hg branches -q
foo
default
bar
Test for invalid branch cache:
$ hg rollback
repository tip rolled back to revision 4 (undo commit)
working directory now based on revisions 4 and 3
$ cp ${branchcache}-served .hg/bc-invalid
$ hg log -r foo
changeset: 4:adf1a74a7f7b
branch: foo
tag: tip
parent: 1:6c0e42da283a
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: modify a branch
$ cp .hg/bc-invalid $branchcache
$ hg --debug log -r foo
changeset: 4:adf1a74a7f7b4cd193d12992f5d0d6a004ed21d6
branch: foo
tag: tip
phase: draft
parent: 1:6c0e42da283a56b5edc5b4fadb491365ec7f5fa8
parent: -1:0000000000000000000000000000000000000000
manifest: 1:8c342a37dfba0b3d3ce073562a00d8a813c54ffe
user: test
date: Thu Jan 01 00:00:00 1970 +0000
files: a
extra: branch=foo
description:
modify a branch
$ purgebranchcaches
$ echo corrupted > $branchcache
$ hg log -qr foo
4:adf1a74a7f7b
$ listbranchcaches
=== .hg/cache/branch2 ===
corrupted
=== .hg/cache/branch2-served ===
adf1a74a7f7b4cd193d12992f5d0d6a004ed21d6 4
c21617b13b220988e7a2e26290fbe4325ffa7139 o bar
1c28f494dae69a2f8fc815059d257eccf3fcfe75 o default
adf1a74a7f7b4cd193d12992f5d0d6a004ed21d6 o foo
Push should update the branch cache:
$ hg init ../target
Pushing just rev 0:
$ hg push -qr 0 ../target
$ (cd ../target/; listbranchcaches)
=== .hg/cache/branch2-base ===
db01e8ea3388fd3c7c94e1436ea2bd6a53d581c5 0
db01e8ea3388fd3c7c94e1436ea2bd6a53d581c5 o default
Pushing everything:
$ hg push -qf ../target
$ (cd ../target/; listbranchcaches)
=== .hg/cache/branch2-base ===
adf1a74a7f7b4cd193d12992f5d0d6a004ed21d6 4
c21617b13b220988e7a2e26290fbe4325ffa7139 o bar
1c28f494dae69a2f8fc815059d257eccf3fcfe75 o default
adf1a74a7f7b4cd193d12992f5d0d6a004ed21d6 o foo
Update with no arguments: tipmost revision of the current branch:
$ hg up -q -C 0
$ hg up -q
$ hg id
1c28f494dae6
$ hg up -q 1
$ hg up -q
$ hg id
adf1a74a7f7b (foo) tip
$ hg branch foobar
marked working directory as branch foobar
$ hg up
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
Fast-forward merge:
$ hg branch ff
marked working directory as branch ff
$ echo ff > ff
$ hg ci -Am'fast forward'
adding ff
$ hg up foo
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg merge ff
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg branch
foo
$ hg commit -m'Merge ff into foo'
$ hg parents
changeset: 6:185ffbfefa30
branch: foo
tag: tip
parent: 4:adf1a74a7f7b
parent: 5:1a3c27dc5e11
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Merge ff into foo
$ hg manifest
a
ff
Test merging, add 3 default heads and one test head:
$ cd ..
$ hg init merges
$ cd merges
$ echo a > a
$ hg ci -Ama
adding a
$ echo b > b
$ hg ci -Amb
adding b
$ hg up 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo c > c
$ hg ci -Amc
adding c
created new head
$ hg up 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo d > d
$ hg ci -Amd
adding d
created new head
$ hg up 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg branch test
marked working directory as branch test
(branches are permanent and global, did you want a bookmark?)
$ echo e >> e
$ hg ci -Ame
adding e
$ hg log
changeset: 4:3a1e01ed1df4
branch: test
tag: tip
parent: 0:cb9a9f314b8b
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: e
changeset: 3:980f7dc84c29
parent: 0:cb9a9f314b8b
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: d
changeset: 2:d36c0562f908
parent: 0:cb9a9f314b8b
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: c
changeset: 1:d2ae7f538514
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: b
changeset: 0:cb9a9f314b8b
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: a
Implicit merge with test branch as parent:
$ hg merge
abort: branch 'test' has one head - please merge with an explicit rev
(run 'hg heads' to see all heads)
[255]
$ hg up -C default
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
Implicit merge with default branch as parent:
$ hg merge
abort: branch 'default' has 3 heads - please merge with an explicit rev
(run 'hg heads .' to see heads)
[255]
3 branch heads, explicit merge required:
$ hg merge 2
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg ci -m merge
2 branch heads, implicit merge works:
$ hg merge
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ cd ..
We expect that bare update on new branch, updates to parent
$ hg init bareupdateonnewbranch
$ cd bareupdateonnewbranch
$ hg update
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ touch a
$ hg commit -A -m "a"
adding a
$ touch b
$ hg commit -A -m "b"
adding b
$ touch c
$ hg commit -A -m "c"
adding c
$ hg update -r 1
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg log -G
o changeset: 2:991a3460af53
| tag: tip
| user: test
| date: Thu Jan 01 00:00:00 1970 +0000
| summary: c
|
@ changeset: 1:0e067c57feba
| user: test
| date: Thu Jan 01 00:00:00 1970 +0000
| summary: b
|
o changeset: 0:3903775176ed
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: a
$ hg branch dev
marked working directory as branch dev
(branches are permanent and global, did you want a bookmark?)
$ hg update
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg summary
parent: 1:0e067c57feba
b
branch: dev
commit: (new branch)
update: (current)
phases: 3 draft
$ cd ..
We need special handling for repositories with no "default" branch because
"null" revision belongs to non-existent "default" branch.
$ hg init nodefault
$ cd nodefault
$ hg branch -q foo
$ touch 0
$ hg ci -Aqm0
$ touch 1
$ hg ci -Aqm1
$ hg update -qr0
$ hg branch -q bar
$ touch 2
$ hg ci -Aqm2
$ hg update -qr0
$ hg branch -q baz
$ touch 3
$ hg ci -Aqm3
$ hg ci --close-branch -m 'close baz'
$ hg update -q null
$ hg log -GT'{rev} {branch}\n'
_ 4 baz
|
o 3 baz
|
| o 2 bar
|/
| o 1 foo
|/
o 0 foo
a) updating from "null" should bring us to the tip-most branch head as
there is no "default" branch:
$ hg update -q null
$ hg id -bn
-1 default
$ hg update
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg id -bn
2 bar
b) but if we are at uncommitted "default" branch, we should stick to the
current revision:
$ hg update -q 0
$ hg branch default
marked working directory as branch default
$ hg id -bn
0 default
$ hg update
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg id -bn
0 default
c) also, if we have uncommitted branch at "null", we should stick to it:
$ hg update -q null
$ hg branch new
marked working directory as branch new
$ hg id -bn
-1 new
$ hg update
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg id -bn
-1 new
$ cd ..
We expect that update --clean discard changes in working directory,
and updates to the head of parent branch.
$ hg init updatebareclean
$ cd updatebareclean
$ hg update --clean
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ touch a
$ hg commit -A -m "a"
adding a
$ touch b
$ hg commit -A -m "b"
adding b
$ touch c
$ hg commit -A -m "c"
adding c
$ hg log
changeset: 2:991a3460af53
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: c
changeset: 1:0e067c57feba
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: b
changeset: 0:3903775176ed
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: a
$ hg update -r 1
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg branch new-branch
marked working directory as branch new-branch
(branches are permanent and global, did you want a bookmark?)
$ echo "aa" >> a
$ hg update --clean
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg status
$ hg branch
default
$ hg parent
changeset: 2:991a3460af53
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: c
We expect that update --clean on non existing parent discards a new branch
and updates to the tipmost non-closed branch head
$ hg update null
0 files updated, 0 files merged, 3 files removed, 0 files unresolved
$ hg branch newbranch
marked working directory as branch newbranch
(branches are permanent and global, did you want a bookmark?)
$ hg update -C
3 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg summary
parent: 2:991a3460af53 tip
c
branch: default
commit: (clean)
update: (current)
phases: 3 draft