commit 3c03e237ab372f495fa2498e925813931ba381da Author: Nick Mathewson nickm@torproject.org Date: Fri Sep 22 15:29:15 2017 -0400
Remove an erroneous 0.5 in compute_weighted_bandwidths()
Back in 0.2.4.3-alpha (e106812a778f537), when we switched from using double to using uint64 for selecting by bandwidth, I got the math wrong: I should have used llround(x), or (uint64_t)(x+0.5), but instead I wrote llround(x+0.5). That means we would always round up, rather than rounding to the closest integer
Fixes bug 23318; bugfix on 0.2.4.3-alpha. --- changes/bug23318 | 7 +++++++ src/or/routerlist.c | 2 +- 2 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/changes/bug23318 b/changes/bug23318 new file mode 100644 index 000000000..32c85eb19 --- /dev/null +++ b/changes/bug23318 @@ -0,0 +1,7 @@ + o Minor bugfixes (path selection): + - When selecting relays by bandwidth, avoid a rounding error that + could sometimes cause load to be imbalanced incorrectly. Previously, + we would always round upwards; now, we round towards the nearest + integer. This had the biggest effect when a relay's weight adjustments + should have given it weight 0, but it got weight 1 instead. + Fixes bug 23318; bugfix on 0.2.4.3-alpha. diff --git a/src/or/routerlist.c b/src/or/routerlist.c index 2365f28fd..faf2eeda5 100644 --- a/src/or/routerlist.c +++ b/src/or/routerlist.c @@ -2713,7 +2713,7 @@ compute_weighted_bandwidths(const smartlist_t *sl, final_weight = weight*this_bw; }
- bandwidths[node_sl_idx] = final_weight + 0.5; + bandwidths[node_sl_idx] = final_weight; } SMARTLIST_FOREACH_END(node);
log_debug(LD_CIRC, "Generated weighted bandwidths for rule %s based "