view tests/test-merge-combination.t @ 42743:8c9a6adec67a

rust-discovery: using the children cache in add_missing

The DAG range computation often needs to get back to very old
revisions, and turns out to be disproportionately long, given
that the end goal is to remove the descendents of the given
missing revisons from the undecided set.

The fast iteration capabilities available in the Rust case make
it possible to avoid the DAG range entirely, at the cost of
precomputing the children cache, and to simply iterate on
children of the given missing revisions.

This is a case where staying on the same side of the interface
between the two languages has clear benefits.

On discoveries with initial undecided sets
small enough to bypass sampling entirely, the total cost of
computing the children cache and the subsequent iteration
becomes better than the Python + C counterpart, which relies on
reachableroots2.

For example, on a repo with more than one million revisions with
an initial undecided set of 11 elements, we get these figures:

Rust version with simple iteration
  addcommons: 57.287us
  first undecided computation: 184.278334ms
  first children cache computation: 131.056us
  addmissings iteration: 42.766us
  first addinfo total: 185.24 ms

Python + C version
  first addcommons: 0.29 ms
  addcommons 0.21 ms
  first undecided computation 191.35 ms
  addmissings 45.75 ms
  first addinfo total: 237.77 ms

On discoveries with large undecided sets, the initial price paid
makes the first addinfo slower than the Python + C version,
but that's more than compensated by the gain in sampling and
subsequent iterations.
Here's an extreme example with an undecided set of a million revisions:

Rust version:
  first undecided computation: 293.842629ms
  first children cache computation: 407.911297ms
  addmissings iteration: 34.312869ms
  first addinfo total: 776.02 ms
  taking initial sample
  query 2: sampling time: 1318.38 ms
  query 2; still undecided: 1005013, sample size is: 200
  addmissings: 143.062us

Python + C version:
  first undecided computation 298.13 ms
  addmissings 80.13 ms
  first addinfo total: 399.62 ms
  taking initial sample
  query 2: sampling time: 3957.23 ms
  query 2; still undecided: 1005013, sample size is: 200
  addmissings 52.88 ms

Differential Revision: https://phab.mercurial-scm.org/D6428

This file shows what hg says are "modified" files for a merge commit
(hg log -T {files}), somewhat exhaustively.
It shows merges that involves files contents changing, and merges that
involve executable bit changing, but not merges with multiple or zero
merge ancestors, nor copies/renames, and nor identical file contents
with different filelog revisions.

genmerges is the workhorse. Given:
- a range function describing the possible values for file a
- a isgood function to filter out uninteresting combination
- a createfile function to actually write the values for file a on the
filesystem
it print a series of lines that look like: abcd C: output of -T {files}
describing the file a at respectively the base, p2, p1, merge
revision. "C" indicates that hg merge had conflicts.
  $ genmerges () {
  >   for base in `range` -; do
  >     for r1 in `range $base` -; do
  >       for r2 in `range $base $r1` -; do
  >         for m in `range $base $r1 $r2` -; do
  >           line="$base$r1$r2$m"
  >           isgood $line || continue
  >           hg init repo
  >           cd repo
  >           make_commit () {
  >             v=$1; msg=$2; file=$3;
  >             if [ $v != - ]; then
  >               createfile $v
  >             else
  >               if [ -f a ]
  >               then rm a
  >               else touch $file
  >               fi
  >             fi
  >             hg commit -q -Am $msg || exit 123
  >           }
  >           echo foo > foo
  >           make_commit $base base b
  >           make_commit $r1 r1 c
  >           hg up -r 0 -q
  >           make_commit $r2 r2 d
  >           hg merge -q -r 1 > ../output 2>&1
  >           if [ $? -ne 0 ]; then rm -f *.orig; hg resolve -m --all -q; fi
  >           if [ -s ../output ]; then conflicts=" C"; else conflicts="  "; fi
  >           make_commit $m m e
  >           if [ $m = $r1 ] && [ $m = $r2 ]
  >           then expected=
  >           elif [ $m = $r1 ]
  >           then if [ $base = $r2 ]
  >                then expected=
  >                else expected=a
  >                fi
  >           elif [ $m = $r2 ]
  >           then if [ $base = $r1 ]
  >                then expected=
  >                else expected=a
  >                fi
  >           else expected=a
  >           fi
  >           got=`hg log -r 3 --template '{files}\n' | tr --delete 'e '`
  >           if [ "$got" = "$expected" ]
  >           then echo "$line$conflicts: agree on \"$got\""
  >           else echo "$line$conflicts: hg said \"$got\", expected \"$expected\""
  >           fi
  >           cd ../
  >           rm -rf repo
  >         done
  >       done
  >     done
  >   done
  > }

All the merges of various file contents.

  $ range () {
  >   max=0
  >   for i in $@; do
  >     if [ $i = - ]; then continue; fi
  >     if [ $i -gt $max ]; then max=$i; fi
  >   done
  >   $TESTDIR/seq.py `expr $max + 1`
  > }
  $ isgood () { true; }
  $ createfile () {
  >   if [ -f a ] && [ "`cat a`" = $1 ]
  >   then touch $file
  >   else echo $v > a
  >   fi
  > }

  $ genmerges
  1111  : agree on ""
  1112  : agree on "a"
  111-  : agree on "a"
  1121  : agree on "a"
  1122  : agree on ""
  1123  : agree on "a"
  112-  : agree on "a"
  11-1  : hg said "", expected "a"
  11-2  : agree on "a"
  11--  : agree on ""
  1211  : agree on "a"
  1212  : agree on ""
  1213  : agree on "a"
  121-  : agree on "a"
  1221  : agree on "a"
  1222  : agree on ""
  1223  : agree on "a"
  122-  : agree on "a"
  1231 C: agree on "a"
  1232 C: agree on "a"
  1233 C: agree on "a"
  1234 C: agree on "a"
  123- C: agree on "a"
  12-1 C: agree on "a"
  12-2 C: hg said "", expected "a"
  12-3 C: agree on "a"
  12-- C: agree on "a"
  1-11  : hg said "", expected "a"
  1-12  : agree on "a"
  1-1-  : agree on ""
  1-21 C: agree on "a"
  1-22 C: hg said "", expected "a"
  1-23 C: agree on "a"
  1-2- C: agree on "a"
  1--1  : agree on "a"
  1--2  : agree on "a"
  1---  : agree on ""
  -111  : agree on ""
  -112  : agree on "a"
  -11-  : agree on "a"
  -121 C: agree on "a"
  -122 C: agree on "a"
  -123 C: agree on "a"
  -12- C: agree on "a"
  -1-1  : agree on ""
  -1-2  : agree on "a"
  -1--  : agree on "a"
  --11  : agree on ""
  --12  : agree on "a"
  --1-  : agree on "a"
  ---1  : agree on "a"
  ----  : agree on ""

All the merges of executable bit.

  $ range () {
  >   max=a
  >   for i in $@; do
  >     if [ $i = - ]; then continue; fi
  >     if [ $i > $max ]; then max=$i; fi
  >   done
  >   if [ $max = a ]; then echo f; else echo f x; fi
  > }
  $ isgood () { case $line in *f*x*) true;; *) false;; esac; }
  $ createfile () {
  >   if [ -f a ] && (([ -x a ] && [ $v = x ]) || (! [ -x a ] && [ $v != x ]))
  >   then touch $file
  >   else touch a; if [ $v = x ]; then chmod +x a; else chmod -x a; fi
  >   fi
  > }

#if execbit
  $ genmerges
  fffx  : agree on "a"
  ffxf  : agree on "a"
  ffxx  : agree on ""
  ffx-  : agree on "a"
  ff-x  : hg said "", expected "a"
  fxff  : hg said "", expected "a"
  fxfx  : hg said "a", expected ""
  fxf-  : agree on "a"
  fxxf  : agree on "a"
  fxxx  : agree on ""
  fxx-  : agree on "a"
  fx-f  : hg said "", expected "a"
  fx-x  : hg said "", expected "a"
  fx--  : hg said "", expected "a"
  f-fx  : agree on "a"
  f-xf  : agree on "a"
  f-xx  : hg said "", expected "a"
  f-x-  : agree on "a"
  f--x  : agree on "a"
  -ffx  : agree on "a"
  -fxf C: agree on "a"
  -fxx C: hg said "", expected "a"
  -fx- C: agree on "a"
  -f-x  : hg said "", expected "a"
  --fx  : agree on "a"
#endif

Files modified or cleanly merged, with no greatest common ancestors:

  $ hg init repo; cd repo
  $ touch a0 b0; hg commit -qAm 0
  $ hg up -qr null; touch a1 b1; hg commit -qAm 1
  $ hg merge -qr 0; rm b*; hg commit -qAm 2
  $ hg log -r . -T '{files}\n'
  b0 b1
  $ cd ../
  $ rm -rf repo

A few cases of criss-cross merges involving deletions (listing all
such merges is probably too much). Both gcas contain $files, so we
expect the final merge to behave like a merge with a single gca
containing $files.

  $ hg init repo; cd repo
  $ files="c1 u1 c2 u2"
  $ touch $files; hg commit -qAm '0 root'
  $ for f in $files; do echo f > $f; done; hg commit -qAm '1 gca1'
  $ hg up -qr0; hg revert -qr 1 --all; hg commit -qAm '2 gca2'
  $ hg up -qr 1; hg merge -qr 2; rm *1; hg commit -qAm '3 p1'
  $ hg up -qr 2; hg merge -qr 1; rm *2; hg commit -qAm '4 p2'
  $ hg merge -qr 3; echo f > u1; echo f > u2; rm -f c1 c2
  $ hg commit -qAm '5 merge with two gcas'
  $ hg log -r . -T '{files}\n' # expecting u1 u2
  
  $ cd ../
  $ rm -rf repo