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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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46 changes: 46 additions & 0 deletions src/api.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -388,6 +388,28 @@ impl<L: Language> Iterator for SyntaxNodeChildren<L> {
}
}

impl<L: Language> SyntaxNodeChildren<L> {
pub fn by_kind<F: Clone + Fn(SyntaxKind) -> bool>(
self,
matcher: F,
) -> SyntaxNodeChildrenMatching<F, L> {
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Suggested change
) -> SyntaxNodeChildrenMatching<F, L> {
) -> SyntaxNodeChildrenByKind<F, L> {

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Changed

SyntaxNodeChildrenMatching { raw: self.raw.by_kind(matcher), _p: PhantomData }
}
}

#[derive(Debug, Clone)]
pub struct SyntaxNodeChildrenMatching<F: Clone + Fn(SyntaxKind) -> bool, L: Language> {
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I'd probably still stick with fn(SyntaxKind) -> bool. Fn trait is indeed more flexible, but that comes at the expense of compile times, as generics break separate compilation. With fn, we compile everything when compiling rowan. With Fn, donstream crates would have to carry compilation time burden.

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Would there be any disadvantage to a &dyn Fn vs. an fn?

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Good question. It'll have to carry a lifetime, and would be two pointers wide, while what we actually need in practice is fn. I guess, my primary intuition here is about avoiding premature generalization.

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@theo-lw theo-lw Oct 24, 2021 •
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I think support::token is a place where we would have to pass a closure to get by_kinds to work. Because of this, I'm using &dyn Fn right now.

raw: cursor::SyntaxNodeChildrenMatching<F>,
_p: PhantomData<L>,
}

impl<F: Clone + Fn(SyntaxKind) -> bool, L: Language> Iterator for SyntaxNodeChildrenMatching<F, L> {
type Item = SyntaxNode<L>;
fn next(&mut self) -> Option<Self::Item> {
self.raw.next().map(SyntaxNode::from)
}
}

#[derive(Debug, Clone)]
pub struct SyntaxElementChildren<L: Language> {
raw: cursor::SyntaxElementChildren,
Expand All @@ -401,6 +423,30 @@ impl<L: Language> Iterator for SyntaxElementChildren<L> {
}
}

impl<L: Language> SyntaxElementChildren<L> {
pub fn by_kind<F: Clone + Fn(SyntaxKind) -> bool>(
self,
matcher: F,
) -> SyntaxElementChildrenMatching<F, L> {
SyntaxElementChildrenMatching { raw: self.raw.by_kind(matcher), _p: PhantomData }
}
}

#[derive(Debug, Clone)]
pub struct SyntaxElementChildrenMatching<F: Clone + Fn(SyntaxKind) -> bool, L: Language> {
raw: cursor::SyntaxElementChildrenMatching<F>,
_p: PhantomData<L>,
}

impl<F: Clone + Fn(SyntaxKind) -> bool, L: Language> Iterator
for SyntaxElementChildrenMatching<F, L>
{
type Item = SyntaxElement<L>;
fn next(&mut self) -> Option<Self::Item> {
self.raw.next().map(NodeOrToken::from)
}
}

pub struct Preorder<L: Language> {
raw: cursor::Preorder,
_p: PhantomData<L>,
Expand Down
198 changes: 196 additions & 2 deletions src/cursor.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -388,6 +388,24 @@ impl NodeData {
})
})
}

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

siblings.nth(index);
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siblings.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 index = rev_siblings.len() - (self.index() as usize);
Expand All @@ -412,6 +430,25 @@ impl NodeData {
Some(SyntaxElement::new(child.as_ref(), parent, index as u32, offset))
})
}

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

siblings.nth(index);
siblings.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 +684,26 @@ impl SyntaxNode {
})
})
}

pub fn first_child_matching(
&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 +722,24 @@ impl SyntaxNode {
SyntaxElement::new(child.as_ref(), self.clone(), 0, self.offset() + child.rel_offset())
})
}

pub fn first_child_or_token_matching(
&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 +754,29 @@ impl SyntaxNode {
pub fn next_sibling(&self) -> Option<SyntaxNode> {
self.data().next_sibling()
}

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

pub fn prev_sibling_or_token(&self) -> Option<SyntaxElement> {
self.data().prev_sibling_or_token()
}
Expand Down Expand Up @@ -910,6 +1001,14 @@ impl SyntaxToken {
pub fn next_sibling_or_token(&self) -> Option<SyntaxElement> {
self.data().next_sibling_or_token()
}

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

pub fn prev_sibling_or_token(&self) -> Option<SyntaxElement> {
self.data().prev_sibling_or_token()
}
Expand Down Expand Up @@ -1028,6 +1127,17 @@ impl SyntaxElement {
NodeOrToken::Token(it) => it.next_sibling_or_token(),
}
}

pub fn next_sibling_or_token_matching(
&self,
matcher: &impl Fn(SyntaxKind) -> bool,
) -> Option<SyntaxElement> {
match self {
NodeOrToken::Node(it) => it.next_sibling_or_token_matching(matcher),
NodeOrToken::Token(it) => it.next_sibling_or_token_matching(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 +1243,130 @@ 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) -> SyntaxNodeChildrenMatching<F> {
if !self.next_initialized {
SyntaxNodeChildrenMatching { next: self.parent.first_child_matching(&matcher), matcher }
} else {
SyntaxNodeChildrenMatching {
next: self.next.and_then(|node| {
if matcher(node.kind()) {
Some(node)
} else {
node.next_sibling_matching(&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 SyntaxNodeChildrenMatching<F: Fn(SyntaxKind) -> bool> {
next: Option<SyntaxNode>,
matcher: F,
}

impl<F: Fn(SyntaxKind) -> bool> Iterator for SyntaxNodeChildrenMatching<F> {
type Item = SyntaxNode;
fn next(&mut self) -> Option<SyntaxNode> {
self.next.take().map(|next| {
self.next = next.next_sibling_matching(&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,
) -> SyntaxElementChildrenMatching<F> {
if !self.next_initialized {
SyntaxElementChildrenMatching {
next: self.parent.first_child_or_token_matching(&matcher),
matcher,
}
} else {
SyntaxElementChildrenMatching {
next: self.next.and_then(|node| {
if matcher(node.kind()) {
Some(node)
} else {
node.next_sibling_or_token_matching(&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 SyntaxElementChildrenMatching<F: Fn(SyntaxKind) -> bool> {
next: Option<SyntaxElement>,
matcher: F,
}

impl<F: Fn(SyntaxKind) -> bool> Iterator for SyntaxElementChildrenMatching<F> {
type Item = SyntaxElement;
fn next(&mut self) -> Option<SyntaxElement> {
self.next.take().map(|next| {
self.next = next.next_sibling_or_token_matching(&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, SyntaxNode, SyntaxNodeChildren,
SyntaxNodeChildrenMatching, SyntaxToken,
},
green::{
Checkpoint, Children, GreenNode, GreenNodeBuilder, GreenNodeData, GreenToken,
Expand Down