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Reduce the number of allocations needed to find a specific child/sibling #119

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Reduce the number of allocations needed to find a specific child/sibling #119

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3d93945
Attempt to reduce the allocations needed to iterate through the child…
theo-lw Oct 3, 2021
fd63d90
Reduce allocations when looking through children with tokens, remove …
theo-lw Oct 3, 2021
05e47e9
Run cargo fmt
theo-lw Oct 3, 2021
9b96915
Moved 'a to children_with_tokens_matching
theo-lw Oct 3, 2021
5d62e45
Expose the api as children().by_kind
theo-lw Oct 23, 2021
0dad088
Remove unnecessary functions, fix off-by-one error
Oct 23, 2021
94b039c
Lazily create SyntaxNodeChildren::next and SyntaxElementChildren::nex…
Oct 24, 2021
bff5da8
Run cargo fmt
Oct 24, 2021
8ba46a7
Change Syntax*ChildrenMatching -> Syntax*ChildrenByKind
Oct 24, 2021
2b94548
Run cargo fmt
Oct 24, 2021
3f283c9
Change function names to use by_kind instead of matching. Use &dyn Fn…
Oct 24, 2021
04e1a2a
Expose SyntaxNodeChildrenByKind
Oct 25, 2021
39b5410
Changes per Veykril's comments
Nov 9, 2021
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56 changes: 56 additions & 0 deletions src/api.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -388,6 +388,34 @@ impl<L: Language> Iterator for SyntaxNodeChildren<L> {
}
}

impl<L: Language> SyntaxNodeChildren<L> {
pub fn by_kind<'a>(
self,
matcher: &'a dyn Fn(SyntaxKind) -> bool,
) -> SyntaxNodeChildrenByKind<'a, L> {
SyntaxNodeChildrenByKind { raw: self.raw.by_kind(matcher), _p: PhantomData }
}
}

#[derive(Clone)]
pub struct SyntaxNodeChildrenByKind<'a, L: Language> {
raw: cursor::SyntaxNodeChildrenByKind<&'a dyn Fn(SyntaxKind) -> bool>,
_p: PhantomData<L>,
}

impl<'a, L: Language> Iterator for SyntaxNodeChildrenByKind<'a, L> {
type Item = SyntaxNode<L>;
fn next(&mut self) -> Option<Self::Item> {
self.raw.next().map(SyntaxNode::from)
}
}

impl<'a, L: Language> fmt::Debug for SyntaxNodeChildrenByKind<'a, L> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("SyntaxNodeChildrenByKind").finish()
}
}

#[derive(Debug, Clone)]
pub struct SyntaxElementChildren<L: Language> {
raw: cursor::SyntaxElementChildren,
Expand All @@ -401,6 +429,34 @@ impl<L: Language> Iterator for SyntaxElementChildren<L> {
}
}

impl<L: Language> SyntaxElementChildren<L> {
pub fn by_kind<'a>(
self,
matcher: &'a dyn Fn(SyntaxKind) -> bool,
) -> SyntaxElementChildrenByKind<'a, L> {
SyntaxElementChildrenByKind { raw: self.raw.by_kind(matcher), _p: PhantomData }
}
}

#[derive(Clone)]
pub struct SyntaxElementChildrenByKind<'a, L: Language> {
raw: cursor::SyntaxElementChildrenByKind<&'a dyn Fn(SyntaxKind) -> bool>,
_p: PhantomData<L>,
}

impl<'a, L: Language> Iterator for SyntaxElementChildrenByKind<'a, L> {
type Item = SyntaxElement<L>;
fn next(&mut self) -> Option<Self::Item> {
self.raw.next().map(NodeOrToken::from)
}
}

impl<'a, L: Language> fmt::Debug for SyntaxElementChildrenByKind<'a, L> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("SyntaxElementChildrenByKind").finish()
}
}

pub struct Preorder<L: Language> {
raw: cursor::Preorder,
_p: PhantomData<L>,
Expand Down
200 changes: 192 additions & 8 deletions src/cursor.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -376,24 +376,39 @@ impl NodeData {
}

fn next_sibling(&self) -> Option<SyntaxNode> {
let mut siblings = self.green_siblings().enumerate();
let siblings = self.green_siblings().enumerate();
let index = self.index() as usize;

siblings.skip(index + 1).find_map(|(index, child)| {
child.as_ref().into_node().and_then(|green| {
let parent = self.parent_node()?;
let offset = parent.offset() + child.rel_offset();
Some(SyntaxNode::new_child(green, parent, index as u32, offset))
})
})
}

fn next_sibling_by_kind(&self, matcher: &impl Fn(SyntaxKind) -> bool) -> Option<SyntaxNode> {
let siblings = self.green_siblings().enumerate();
let index = self.index() as usize;

siblings.nth(index);
siblings.find_map(|(index, child)| {
siblings.skip(index + 1).find_map(|(index, child)| {
if !matcher(child.as_ref().kind()) {
return None;
}
child.as_ref().into_node().and_then(|green| {
let parent = self.parent_node()?;
let offset = parent.offset() + child.rel_offset();
Some(SyntaxNode::new_child(green, parent, index as u32, offset))
})
})
}

fn prev_sibling(&self) -> Option<SyntaxNode> {
let mut rev_siblings = self.green_siblings().enumerate().rev();
let rev_siblings = self.green_siblings().enumerate().rev();
let index = rev_siblings.len() - (self.index() as usize);

rev_siblings.nth(index);
rev_siblings.find_map(|(index, child)| {
rev_siblings.skip(index + 1).find_map(|(index, child)| {
child.as_ref().into_node().and_then(|green| {
let parent = self.parent_node()?;
let offset = parent.offset() + child.rel_offset();
Expand All @@ -412,6 +427,24 @@ impl NodeData {
Some(SyntaxElement::new(child.as_ref(), parent, index as u32, offset))
})
}

fn next_sibling_or_token_by_kind(
&self,
matcher: &impl Fn(SyntaxKind) -> bool,
) -> Option<SyntaxElement> {
let siblings = self.green_siblings().enumerate();
let index = self.index() as usize;

siblings.skip(index + 1).find_map(|(index, child)| {
if !matcher(child.as_ref().kind()) {
return None;
}
let parent = self.parent_node()?;
let offset = parent.offset() + child.rel_offset();
Some(SyntaxElement::new(child.as_ref(), parent, index as u32, offset))
})
}

fn prev_sibling_or_token(&self) -> Option<SyntaxElement> {
let mut siblings = self.green_siblings().enumerate();
let index = self.index().checked_sub(1)? as usize;
Expand Down Expand Up @@ -647,6 +680,23 @@ impl SyntaxNode {
})
})
}

pub fn first_child_by_kind(&self, matcher: &impl Fn(SyntaxKind) -> bool) -> Option<SyntaxNode> {
self.green_ref().children().raw.enumerate().find_map(|(index, child)| {
if !matcher(child.as_ref().kind()) {
return None;
}
child.as_ref().into_node().map(|green| {
SyntaxNode::new_child(
green,
self.clone(),
index as u32,
self.offset() + child.rel_offset(),
)
})
})
}

pub fn last_child(&self) -> Option<SyntaxNode> {
self.green_ref().children().raw.enumerate().rev().find_map(|(index, child)| {
child.as_ref().into_node().map(|green| {
Expand All @@ -665,6 +715,24 @@ impl SyntaxNode {
SyntaxElement::new(child.as_ref(), self.clone(), 0, self.offset() + child.rel_offset())
})
}

pub fn first_child_or_token_by_kind(
&self,
matcher: &impl Fn(SyntaxKind) -> bool,
) -> Option<SyntaxElement> {
self.green_ref().children().raw.enumerate().find_map(|(index, child)| {
if !matcher(child.as_ref().kind()) {
return None;
}
Some(SyntaxElement::new(
child.as_ref(),
self.clone(),
index as u32,
self.offset() + child.rel_offset(),
))
})
}

pub fn last_child_or_token(&self) -> Option<SyntaxElement> {
self.green_ref().children().raw.enumerate().next_back().map(|(index, child)| {
SyntaxElement::new(
Expand All @@ -679,13 +747,29 @@ impl SyntaxNode {
pub fn next_sibling(&self) -> Option<SyntaxNode> {
self.data().next_sibling()
}

pub fn next_sibling_by_kind(
&self,
matcher: &impl Fn(SyntaxKind) -> bool,
) -> Option<SyntaxNode> {
self.data().next_sibling_by_kind(matcher)
}

pub fn prev_sibling(&self) -> Option<SyntaxNode> {
self.data().prev_sibling()
}

pub fn next_sibling_or_token(&self) -> Option<SyntaxElement> {
self.data().next_sibling_or_token()
}

pub fn next_sibling_or_token_by_kind(
&self,
matcher: &impl Fn(SyntaxKind) -> bool,
) -> Option<SyntaxElement> {
self.data().next_sibling_or_token_by_kind(matcher)
}

pub fn prev_sibling_or_token(&self) -> Option<SyntaxElement> {
self.data().prev_sibling_or_token()
}
Expand Down Expand Up @@ -910,6 +994,14 @@ impl SyntaxToken {
pub fn next_sibling_or_token(&self) -> Option<SyntaxElement> {
self.data().next_sibling_or_token()
}

pub fn next_sibling_or_token_by_kind(
&self,
matcher: &impl Fn(SyntaxKind) -> bool,
) -> Option<SyntaxElement> {
self.data().next_sibling_or_token_by_kind(matcher)
}

pub fn prev_sibling_or_token(&self) -> Option<SyntaxElement> {
self.data().prev_sibling_or_token()
}
Expand Down Expand Up @@ -1028,6 +1120,17 @@ impl SyntaxElement {
NodeOrToken::Token(it) => it.next_sibling_or_token(),
}
}

pub fn next_sibling_or_token_by_kind(
&self,
matcher: &impl Fn(SyntaxKind) -> bool,
) -> Option<SyntaxElement> {
match self {
NodeOrToken::Node(it) => it.next_sibling_or_token_by_kind(matcher),
NodeOrToken::Token(it) => it.next_sibling_or_token_by_kind(matcher),
}
}

pub fn prev_sibling_or_token(&self) -> Option<SyntaxElement> {
match self {
NodeOrToken::Node(it) => it.prev_sibling_or_token(),
Expand Down Expand Up @@ -1133,46 +1236,127 @@ impl From<SyntaxToken> for SyntaxElement {

#[derive(Clone, Debug)]
pub struct SyntaxNodeChildren {
parent: SyntaxNode,
next: Option<SyntaxNode>,
next_initialized: bool,
}

impl SyntaxNodeChildren {
fn new(parent: SyntaxNode) -> SyntaxNodeChildren {
SyntaxNodeChildren { next: parent.first_child() }
SyntaxNodeChildren { parent, next: None, next_initialized: false }
}

pub fn by_kind<F: Fn(SyntaxKind) -> bool>(self, matcher: F) -> SyntaxNodeChildrenByKind<F> {
if !self.next_initialized {
SyntaxNodeChildrenByKind { next: self.parent.first_child_by_kind(&matcher), matcher }
} else {
SyntaxNodeChildrenByKind {
next: self.next.and_then(|node| {
if matcher(node.kind()) {
Some(node)
} else {
node.next_sibling_by_kind(&matcher)
}
}),
matcher,
}
}
}
}

impl Iterator for SyntaxNodeChildren {
type Item = SyntaxNode;
fn next(&mut self) -> Option<SyntaxNode> {
if !self.next_initialized {
self.next = self.parent.first_child();
self.next_initialized = true;
}
self.next.take().map(|next| {
self.next = next.next_sibling();
next
})
}
}

#[derive(Clone, Debug)]
pub struct SyntaxNodeChildrenByKind<F: Fn(SyntaxKind) -> bool> {
next: Option<SyntaxNode>,
matcher: F,
}

impl<F: Fn(SyntaxKind) -> bool> Iterator for SyntaxNodeChildrenByKind<F> {
type Item = SyntaxNode;
fn next(&mut self) -> Option<SyntaxNode> {
self.next.take().map(|next| {
self.next = next.next_sibling_by_kind(&self.matcher);
next
})
}
}

#[derive(Clone, Debug)]
pub struct SyntaxElementChildren {
parent: SyntaxNode,
next: Option<SyntaxElement>,
next_initialized: bool,
Comment on lines +1299 to +1301
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Hm, why do we need to change anything here? I'd expect SyntaxElementChildren to remain exactly as they were

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Good question. I changed this so we could avoid creating SyntaxElementChildren::next when calling children().by_kind. This actually makes a pretty significant impact - here's the DHAT output of the integrated completions benchmark without this optimization:

Screen Shot 2021-10-24 at 11 29 39 AM

And here's the DHAT output of the integrated completions benchmark after this optimization:

Screen Shot 2021-10-23 at 11 19 05 PM

98 million blocks allocated (before this optimization) vs 86 million blocks allocated (after this optimization).

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@Veykril Veykril Nov 8, 2021 •
edited
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Sounds odd to me that using first_child_or_token_by_kind with these extra changes is so much faster than seeking to the next sibling via next_sibling_or_token_by_kind, as both ways come down to iterating a slice no?

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Hmm, my observation is that using first_child_or_token_by_kind allows us to jump to the first child/token node that matches a kind without needing to allocate any other nodes. Contrast this to using first_child_or_token followed by next_sibling_or_token_by_kind (if the first child doesn't match the kind), which can potentially allocate the first child before jumping to the desired node. I think its this allocation avoidance that explains the improvement in the DHAT outputs.

}

impl SyntaxElementChildren {
fn new(parent: SyntaxNode) -> SyntaxElementChildren {
SyntaxElementChildren { next: parent.first_child_or_token() }
SyntaxElementChildren { parent, next: None, next_initialized: false }
}

pub fn by_kind<F: Fn(SyntaxKind) -> bool>(self, matcher: F) -> SyntaxElementChildrenByKind<F> {
if !self.next_initialized {
SyntaxElementChildrenByKind {
next: self.parent.first_child_or_token_by_kind(&matcher),
matcher,
}
} else {
SyntaxElementChildrenByKind {
next: self.next.and_then(|node| {
if matcher(node.kind()) {
Some(node)
} else {
node.next_sibling_or_token_by_kind(&matcher)
}
}),
matcher,
}
}
}
}

impl Iterator for SyntaxElementChildren {
type Item = SyntaxElement;
fn next(&mut self) -> Option<SyntaxElement> {
if !self.next_initialized {
self.next = self.parent.first_child_or_token();
self.next_initialized = true;
}
self.next.take().map(|next| {
self.next = next.next_sibling_or_token();
next
})
}
}

#[derive(Clone, Debug)]
pub struct SyntaxElementChildrenByKind<F: Fn(SyntaxKind) -> bool> {
next: Option<SyntaxElement>,
matcher: F,
}

impl<F: Fn(SyntaxKind) -> bool> Iterator for SyntaxElementChildrenByKind<F> {
type Item = SyntaxElement;
fn next(&mut self) -> Option<SyntaxElement> {
self.next.take().map(|next| {
self.next = next.next_sibling_or_token_by_kind(&self.matcher);
next
})
}
}

pub struct Preorder {
start: SyntaxNode,
next: Option<WalkEvent<SyntaxNode>>,
Expand Down
3 changes: 2 additions & 1 deletion src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -29,7 +29,8 @@ pub use text_size::{TextLen, TextRange, TextSize};

pub use crate::{
api::{
Language, SyntaxElement, SyntaxElementChildren, SyntaxNode, SyntaxNodeChildren, SyntaxToken,
Language, SyntaxElement, SyntaxElementChildren, SyntaxElementChildrenByKind, SyntaxNode,
SyntaxNodeChildren, SyntaxNodeChildrenByKind, SyntaxToken,
},
green::{
Checkpoint, Children, GreenNode, GreenNodeBuilder, GreenNodeData, GreenToken,
Expand Down