comparison tests/test-setdiscovery.t @ 23813:932f814bf016

setdiscovery: always add exponential sample to the heads

As explained in a previous changeset, prioritizing heads too much behaves
pathologically when there are more heads than the sample size. To counter this,
we always inject exponential samples before reducing to the sample size limit.

This already show some benefit in the test themselves, but on a real-world example
this moves my discovery for push to pathologically headed repo from 45 rounds to
17 of them.

We should maybe ensure that at least 25% of the result sample is heads, but I
think the random sampling will be fine in practice.

23812:db58186dd8e3

  sampling from both directions
  searching: 3 queries
  query 3; still undecided: 1140, sample size is: 200
  sampling from both directions
  searching: 4 queries
  query 4; still undecided: 940, sample size is: 200
  sampling from both directions
  searching: 5 queries
  query 5; still undecided: 740, sample size is: 200
  sampling from both directions
  searching: 6 queries
  query 6; still undecided: 540, sample size is: 200
  sampling from both directions
  searching: 7 queries
  query 7; still undecided: 46, sample size is: 46
  7 total queries
  common heads: 3ee37d65064a

Test actual protocol when pulling one new head in addition to common heads

  $ hg clone -U b c

23813:932f814bf016

  sampling from both directions
  searching: 3 queries
  query 3; still undecided: 1140, sample size is: 200
  sampling from both directions
  searching: 4 queries
  query 4; still undecided: 592, sample size is: 200
  sampling from both directions
  searching: 5 queries
  query 5; still undecided: 292, sample size is: 200
  sampling from both directions
  searching: 6 queries
  query 6; still undecided: 51, sample size is: 51
  6 total queries
  common heads: 3ee37d65064a

Test actual protocol when pulling one new head in addition to common heads

  $ hg clone -U b c