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
This test test the low-level definition of stack, agnostic from all formatting
Initial setup
$ cat << EOF >> $HGRCPATH
> [ui]
> logtemplate = {rev} {branch} {phase} {desc|firstline}\n
> [extensions]
> rebase=
> [experimental]
> evolution=createmarkers,exchange,allowunstable
> EOF
$ hg init main
$ cd main
$ hg branch other
marked working directory as branch other
(branches are permanent and global, did you want a bookmark?)
$ echo aaa > aaa
$ hg add aaa
$ hg commit -m c_a
$ echo aaa > bbb
$ hg add bbb
$ hg commit -m c_b
$ hg branch foo
marked working directory as branch foo
$ echo aaa > ccc
$ hg add ccc
$ hg commit -m c_c
$ echo aaa > ddd
$ hg add ddd
$ hg commit -m c_d
$ echo aaa > eee
$ hg add eee
$ hg commit -m c_e
$ echo aaa > fff
$ hg add fff
$ hg commit -m c_f
$ hg log -G
@ 5 foo draft c_f
|
o 4 foo draft c_e
|
o 3 foo draft c_d
|
o 2 foo draft c_c
|
o 1 other draft c_b
|
o 0 other draft c_a
Check that stack doesn't include public changesets
--------------------------------------------------
$ hg up other
0 files updated, 0 files merged, 4 files removed, 0 files unresolved
$ hg log -G -r "stack()"
@ 1 other draft c_b
|
o 0 other draft c_a
$ hg phase --public 'branch("other")'
$ hg log -G -r "stack()"
$ hg up foo
4 files updated, 0 files merged, 0 files removed, 0 files unresolved
Simple test
-----------
'stack()' list all changeset in the branch
$ hg branch
foo
$ hg log -G -r "stack()"
@ 5 foo draft c_f
|
o 4 foo draft c_e
|
o 3 foo draft c_d
|
o 2 foo draft c_c
|
~
Case with some of the branch unstable
------------------------------------
$ hg up 3
0 files updated, 0 files merged, 2 files removed, 0 files unresolved
$ echo bbb > ddd
$ hg commit --amend
2 new orphan changesets
$ hg log -G
@ 6 foo draft c_d
|
| * 5 foo draft c_f
| |
| * 4 foo draft c_e
| |
| x 3 foo draft c_d
|/
o 2 foo draft c_c
|
o 1 other public c_b
|
o 0 other public c_a
$ hg log -G -r "stack()"
@ 6 foo draft c_d
|
~
$ hg up -r "desc(c_e)"
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg log -G -r "stack()"
@ 4 foo draft c_e
|
x 3 foo draft c_d
|
~
$ hg up -r "desc(c_d)"
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg log -G -r "stack()"
@ 6 foo draft c_d
|
~
Case with multiple topological heads
------------------------------------
Make things linear again
$ hg rebase -s 'desc(c_e)' -d 'desc(c_d) - obsolete()'
rebasing 4:4f2a69f6d380 "c_e"
rebasing 5:913c298d8b0a "c_f"
$ hg log -G
o 8 foo draft c_f
|
o 7 foo draft c_e
|
@ 6 foo draft c_d
|
o 2 foo draft c_c
|
o 1 other public c_b
|
o 0 other public c_a
Create the second branch
$ hg up 'desc(c_d)'
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo aaa > ggg
$ hg add ggg
$ hg commit -m c_g
created new head
$ echo aaa > hhh
$ hg add hhh
$ hg commit -m c_h
$ hg log -G
@ 10 foo draft c_h
|
o 9 foo draft c_g
|
| o 8 foo draft c_f
| |
| o 7 foo draft c_e
|/
o 6 foo draft c_d
|
o 2 foo draft c_c
|
o 1 other public c_b
|
o 0 other public c_a
Test output
$ hg log -G -r "stack(10)"
@ 10 foo draft c_h
|
o 9 foo draft c_g
|
~
$ hg log -G -r "stack(8)"
o 8 foo draft c_f
|
o 7 foo draft c_e
|
~
$ hg log -G -r "stack(head())"
@ 10 foo draft c_h
|
o 9 foo draft c_g
|
~
o 8 foo draft c_f
|
o 7 foo draft c_e
|
~
Check the stack order
$ hg log -r "first(stack())"
9 foo draft c_g
$ hg log -r "first(stack(10))"
9 foo draft c_g
$ hg log -r "first(stack(8))"
7 foo draft c_e
$ hg log -r "first(stack(head()))"
7 foo draft c_e
Case with multiple heads with unstability involved
--------------------------------------------------
We amend the message to make sure the display base pick the right changeset
$ hg up 'desc(c_d)'
0 files updated, 0 files merged, 2 files removed, 0 files unresolved
$ echo ccc > ddd
$ hg commit --amend -m 'c_D'
4 new orphan changesets
$ hg rebase -d . -s 'desc(c_g)'
rebasing 9:2ebb6e48ab8a "c_g"
rebasing 10:634f38e27a1d "c_h"
$ hg log -G
o 13 foo draft c_h
|
o 12 foo draft c_g
|
@ 11 foo draft c_D
|
| * 8 foo draft c_f
| |
| * 7 foo draft c_e
| |
| x 6 foo draft c_d
|/
o 2 foo draft c_c
|
o 1 other public c_b
|
o 0 other public c_a
We should improve stack definition to also show 12 and 13 here
$ hg log -G -r "stack()"
@ 11 foo draft c_D
|
~