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Use thread-local buffer for occurs check seen variables
This materially improves performance for programs that are
recursion-heavy (as most Roc programs will likely be).
```
$ hyperfine '/tmp/roc-old check examples/cli/cli-platform/Arg.roc' '/tmp/roc-new check examples/cli/cli-platform/Arg.roc' --warmup 10
Benchmark 1: /tmp/roc-old check examples/cli/cli-platform/Arg.roc
Time (mean ± σ): 53.8 ms ± 1.3 ms [User: 87.3 ms, System: 10.8 ms]
Range (min … max): 52.2 ms … 60.4 ms 51 runs
Benchmark 2: /tmp/roc-new check examples/cli/cli-platform/Arg.roc
Time (mean ± σ): 45.0 ms ± 1.6 ms [User: 59.4 ms, System: 11.3 ms]
Range (min … max): 42.6 ms … 49.8 ms 60 runs
Summary
'/tmp/roc-new check examples/cli/cli-platform/Arg.roc' ran
1.20 ± 0.05 times faster than '/tmp/roc-old check examples/cli/cli-platform/Arg.roc'
```
The time spent in `occurs` during checking for `Arg` drops from 50% to 23%.
This commit is contained in:
Ayaz Hafiz
parent
c5afc5e237
commit
2d57aa2170
1 changed files with 62 additions and 54 deletions
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@ -1951,7 +1951,10 @@ impl Subs {
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/// This ignores [Content::RecursionVar]s that occur recursively, because those are
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/// already priced in and expected to occur.
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pub fn occurs(&self, var: Variable) -> Result<(), (Variable, Vec<Variable>)> {
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occurs(self, &[], var)
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let mut scratchpad = take_occurs_scratchpad();
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let result = occurs(self, &mut scratchpad, var);
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put_occurs_scratchpad(scratchpad);
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result
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}
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pub fn mark_tag_union_recursive(
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@ -3196,9 +3199,24 @@ fn is_empty_record(subs: &Subs, mut var: Variable) -> bool {
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}
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}
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std::thread_local! {
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static SCRATCHPAD_FOR_OCCURS: RefCell<Option<Vec<Variable>>> = RefCell::new(Some(Vec::with_capacity(1024)));
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}
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fn take_occurs_scratchpad() -> Vec<Variable> {
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SCRATCHPAD_FOR_OCCURS.with(|f| f.take().unwrap())
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}
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fn put_occurs_scratchpad(mut scratchpad: Vec<Variable>) {
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SCRATCHPAD_FOR_OCCURS.with(|f| {
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scratchpad.clear();
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f.replace(Some(scratchpad));
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});
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}
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fn occurs(
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subs: &Subs,
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seen: &[Variable],
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seen: &mut Vec<Variable>,
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input_var: Variable,
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) -> Result<(), (Variable, Vec<Variable>)> {
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use self::Content::*;
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@ -3207,9 +3225,10 @@ fn occurs(
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let root_var = subs.get_root_key_without_compacting(input_var);
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if seen.contains(&root_var) {
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Err((root_var, vec![]))
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Err((root_var, Vec::with_capacity(0)))
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} else {
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match subs.get_content_without_compacting(root_var) {
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seen.push(root_var);
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let result = (|| match subs.get_content_without_compacting(root_var) {
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FlexVar(_)
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| RigidVar(_)
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| FlexAbleVar(_, _)
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@ -3217,54 +3236,44 @@ fn occurs(
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| RecursionVar { .. }
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| Error => Ok(()),
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Structure(flat_type) => {
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let mut new_seen = seen.to_owned();
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new_seen.push(root_var);
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match flat_type {
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Apply(_, args) => {
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short_circuit(subs, root_var, &new_seen, subs.get_subs_slice(*args).iter())
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}
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Func(arg_vars, closure_var, ret_var) => {
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let it = once(ret_var)
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.chain(once(closure_var))
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.chain(subs.get_subs_slice(*arg_vars).iter());
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short_circuit(subs, root_var, &new_seen, it)
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}
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Record(vars_by_field, ext_var) => {
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let slice =
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SubsSlice::new(vars_by_field.variables_start, vars_by_field.length);
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let it = once(ext_var).chain(subs.get_subs_slice(slice).iter());
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short_circuit(subs, root_var, &new_seen, it)
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}
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TagUnion(tags, ext_var) => {
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occurs_union(subs, root_var, &new_seen, tags)?;
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short_circuit_help(subs, root_var, &new_seen, *ext_var)
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}
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FunctionOrTagUnion(_, _, ext_var) => {
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let it = once(ext_var);
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short_circuit(subs, root_var, &new_seen, it)
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}
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RecursiveTagUnion(_, tags, ext_var) => {
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occurs_union(subs, root_var, &new_seen, tags)?;
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short_circuit_help(subs, root_var, &new_seen, *ext_var)
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}
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EmptyRecord | EmptyTagUnion => Ok(()),
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Structure(flat_type) => match flat_type {
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Apply(_, args) => {
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short_circuit(subs, root_var, seen, subs.get_subs_slice(*args).iter())
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}
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}
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Alias(_, args, real_var, _) => {
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let mut new_seen = seen.to_owned();
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new_seen.push(root_var);
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Func(arg_vars, closure_var, ret_var) => {
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let it = once(ret_var)
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.chain(once(closure_var))
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.chain(subs.get_subs_slice(*arg_vars).iter());
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short_circuit(subs, root_var, seen, it)
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}
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Record(vars_by_field, ext_var) => {
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let slice = SubsSlice::new(vars_by_field.variables_start, vars_by_field.length);
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let it = once(ext_var).chain(subs.get_subs_slice(slice).iter());
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short_circuit(subs, root_var, seen, it)
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}
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TagUnion(tags, ext_var) => {
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occurs_union(subs, root_var, seen, tags)?;
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short_circuit_help(subs, root_var, seen, *ext_var)
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}
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FunctionOrTagUnion(_, _, ext_var) => {
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let it = once(ext_var);
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short_circuit(subs, root_var, seen, it)
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}
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RecursiveTagUnion(_, tags, ext_var) => {
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occurs_union(subs, root_var, seen, tags)?;
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short_circuit_help(subs, root_var, seen, *ext_var)
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}
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EmptyRecord | EmptyTagUnion => Ok(()),
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},
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Alias(_, args, real_var, _) => {
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for var_index in args.into_iter() {
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let var = subs[var_index];
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if short_circuit_help(subs, root_var, &new_seen, var).is_err() {
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if short_circuit_help(subs, root_var, seen, var).is_err() {
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// Pay the cost and figure out what the actual recursion point is
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return short_circuit_help(subs, root_var, &new_seen, *real_var);
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return short_circuit_help(subs, root_var, seen, *real_var);
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}
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}
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@ -3276,16 +3285,15 @@ fn occurs(
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unspecialized: _,
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ambient_function: _,
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}) => {
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let mut new_seen = seen.to_owned();
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new_seen.push(root_var);
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// unspecialized lambda vars excluded because they are not explicitly part of the
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// type (they only matter after being resolved).
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occurs_union(subs, root_var, &new_seen, solved)
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occurs_union(subs, root_var, seen, solved)
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}
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RangedNumber(_range_vars) => Ok(()),
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}
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})();
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seen.pop();
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result
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}
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}
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@ -3293,7 +3301,7 @@ fn occurs(
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fn occurs_union<L: Label>(
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subs: &Subs,
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root_var: Variable,
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seen: &[Variable],
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seen: &mut Vec<Variable>,
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tags: &UnionLabels<L>,
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) -> Result<(), (Variable, Vec<Variable>)> {
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for slice_index in tags.variables() {
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@ -3310,7 +3318,7 @@ fn occurs_union<L: Label>(
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fn short_circuit<'a, T>(
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subs: &Subs,
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root_key: Variable,
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seen: &[Variable],
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seen: &mut Vec<Variable>,
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iter: T,
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) -> Result<(), (Variable, Vec<Variable>)>
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where
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@ -3327,7 +3335,7 @@ where
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fn short_circuit_help(
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subs: &Subs,
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root_key: Variable,
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seen: &[Variable],
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seen: &mut Vec<Variable>,
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var: Variable,
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) -> Result<(), (Variable, Vec<Variable>)> {
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if let Err((v, mut vec)) = occurs(subs, seen, var) {
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