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Faster resolver: clean code and the backtrack_stack #5187

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merged 8 commits into from
Mar 17, 2018
Merged

Faster resolver: clean code and the backtrack_stack #5187

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15c757a
Clean the `backtrack_stack` so we don't backtrack to a place with cas…
Eh2406 Mar 15, 2018
617856e
add a test
Eh2406 Mar 15, 2018
1291c50
cargo +stable fmt
Eh2406 Mar 15, 2018
68e9577
suggestions
Eh2406 Mar 16, 2018
59249d1
remove duplicated adding to the cache
Eh2406 Mar 16, 2018
f5a0f28
Revert "Clean the `backtrack_stack` so we don't backtrack to a place …
Eh2406 Mar 16, 2018
dd9ff1f
When test backtracking include conflicts in `remaining_candidates`
Eh2406 Mar 17, 2018
c771a4c
When activating for the better error messages don't waste time on the…
Eh2406 Mar 17, 2018
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96 changes: 48 additions & 48 deletions src/cargo/core/resolver/mod.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -951,12 +951,9 @@ fn activate_deps_loop(
&& past_conflicting_activations
.get(&dep)
.and_then(|past_bad| {
past_bad.iter().find(|conflicting| {
conflicting
.iter()
// note: a lot of redundant work in is_active for similar debs
.all(|(con, _)| cx.is_active(con))
})
past_bad
.iter()
.find(|conflicting| cx.is_conflicting(None, conflicting))
})
.is_some();

Expand Down Expand Up @@ -1081,61 +1078,53 @@ fn activate_deps_loop(

match res {
Ok(Some((mut frame, dur))) => {
// at this point we have technical already activated
// at this point we have technically already activated
// but we may want to scrap it if it is not going to end well
let mut has_past_conflicting_dep = just_here_for_the_error_messages;
if !has_past_conflicting_dep {
if let Some(conflicting) = frame
.remaining_siblings
.clone()
.filter_map(|(_, (deb, _, _))| {
past_conflicting_activations.get(&deb).and_then(|past_bad| {
// for each dependency check all of its cashed conflicts
past_bad.iter().find(|conflicting| {
conflicting
.iter()
// note: a lot of redundant work in is_active for similar debs
.all(|(con, _)| cx.is_active(con))
})
})
.filter_map(|(_, (new_dep, _, _))| {
past_conflicting_activations.get(&new_dep)
})
.next()
.flat_map(|x| x)
.find(|con| cx.is_conflicting(None, con))
{
// if any of them match than it will just backtrack to us
// so let's save the effort.
conflicting_activations.extend(conflicting.clone());
has_past_conflicting_dep = true;
}
}
if !has_another && has_past_conflicting_dep && !backtracked {
// we have not activated ANY candidates and
// we are out of choices so add it to the cache
// so our parent will know that we don't work
let past = past_conflicting_activations
.entry(dep.clone())
.or_insert_with(Vec::new);
if !past.contains(&conflicting_activations) {
trace!(
"{}[{}]>{} adding a meta-skip {:?}",
parent.name(),
cur,
dep.name(),
conflicting_activations
);
past.push(conflicting_activations.clone());
let activate_for_error_message = has_past_conflicting_dep && !has_another && {
// has_past_conflicting_dep -> One of this candidate deps will fail.
// !has_another -> If the candidate is not accepted we will backtrack.

// So the question is will the user see that we skipped this candidate?
just_here_for_the_error_messages || {
// make sure we know about all the possible conflicts
conflicting_activations
.extend(remaining_candidates.conflicting_prev_active.clone());
// test if backtracking will get to the user
find_candidate(
&mut backtrack_stack.clone(),
&parent,
&conflicting_activations,
).is_none()
}
};
if activate_for_error_message {
// We know one of this candidate deps will fail,
// which means we will fail,
// and that none of the backtrack frames will
// find a candidate that will help.
// So lets clean up the useless backtrack frames.
backtrack_stack.clear();
}
// if not has_another we we activate for the better error messages
frame.just_for_error_messages = has_past_conflicting_dep;
if !has_past_conflicting_dep
|| (!has_another
&& (just_here_for_the_error_messages
|| find_candidate(
&mut backtrack_stack.clone(),
&parent,
&conflicting_activations,
).is_none()))
{
if !has_past_conflicting_dep || activate_for_error_message {
remaining_deps.push(frame);
} else {
trace!(
Expand Down Expand Up @@ -1195,11 +1184,9 @@ fn find_candidate<'a>(
frame.context_backup.prev_active(&frame.dep),
&frame.context_backup.links,
);
if frame.context_backup.is_active(parent.package_id())
&& conflicting_activations
.iter()
// note: a lot of redundant work in is_active for similar debs
.all(|(con, _)| frame.context_backup.is_active(con))
if frame
.context_backup
.is_conflicting(Some(parent.package_id()), conflicting_activations)
{
continue;
}
Expand Down Expand Up @@ -1643,6 +1630,19 @@ impl Context {
.unwrap_or(false)
}

/// checks whether all of `parent` and the keys of `conflicting activations`
/// are still active
fn is_conflicting(
&self,
parent: Option<&PackageId>,
conflicting_activations: &HashMap<PackageId, ConflictReason>,
) -> bool {
conflicting_activations
.keys()
.chain(parent)
.all(|id| self.is_active(id))
}

/// Return all dependencies and the features we want from them.
fn resolve_features<'b>(
&mut self,
Expand Down
43 changes: 43 additions & 0 deletions tests/testsuite/resolve.rs
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -608,6 +608,49 @@ fn resolving_with_many_equivalent_backtracking() {
assert!(res.is_err());
}

#[test]
fn resolving_with_deep_traps() {
let mut reglist = Vec::new();

const DEPTH: usize = 200;
const BRANCHING_FACTOR: usize = 100;

// Each backtrack_trap depends on the next, and adds a backtrack frame.
// None of witch is going to help with `bad`.
for l in 0..DEPTH {
let name = format!("backtrack_trap{}", l);
let next = format!("backtrack_trap{}", l + 1);
for i in 1..BRANCHING_FACTOR {
let vsn = format!("1.0.{}", i);
reglist.push(pkg!((name.as_str(), vsn.as_str()) => [dep_req(next.as_str(), "*")]));
}
}
{
let name = format!("backtrack_trap{}", DEPTH);
for i in 1..BRANCHING_FACTOR {
let vsn = format!("1.0.{}", i);
reglist.push(pkg!((name.as_str(), vsn.as_str())));
}
}
{
// slightly less constrained to make sure `cloaking` gets picked last.
for i in 1..(BRANCHING_FACTOR + 10) {
let vsn = format!("1.0.{}", i);
reglist.push(pkg!(("cloaking", vsn.as_str()) => [dep_req("bad", "1.0.1")]));
}
}

let reg = registry(reglist.clone());

let res = resolve(
&pkg_id("root"),
vec![dep_req("backtrack_trap0", "*"), dep_req("cloaking", "*")],
&reg,
);

assert!(res.is_err());
}

#[test]
fn resolving_with_constrained_sibling_backtrack_activation() {
// It makes sense to resolve most-constrained deps first, but
Expand Down