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Refactor topo-order alg out of sierra-gas.
In preparation for ap-change solve. commit-id:eb28e7c1
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1 @@ | ||
| pub mod topological_order; |
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crates/cairo-lang-sierra/src/algorithm/topological_order.rs
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,110 @@ | ||
| use crate::program::StatementIdx; | ||
|
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| /// The status of a node during the topological ordering finding algorithm. | ||
| #[derive(Clone, Debug)] | ||
| enum TopologicalOrderStatus { | ||
| /// The computation for that statement did not start. | ||
| NotStarted, | ||
| /// The computation is in progress. | ||
| InProgress, | ||
| /// The computation was completed, and all the children were visited. | ||
| Done, | ||
| } | ||
|
|
||
| /// Returns the topological ordering. | ||
| /// `detect_cycles` - if true, the function will return an error if a cycle is detected. | ||
| /// `roots` - the roots of the graph. | ||
| /// `node_count` - the number of nodes in the graph. | ||
| /// `get_children` - a function that returns the children of a node. | ||
| /// `out_of_bounds_err` - a function that returns an error for a node is out of bounds. | ||
| /// `cycle_err` - a function that returns an error for a node that is part of a cycle. | ||
| /// Note: Will only work properly if the nodes are in the range [0, node_count). | ||
| pub fn get_topological_ordering<E>( | ||
| detect_cycles: bool, | ||
| roots: impl Iterator<Item = StatementIdx>, | ||
| node_count: usize, | ||
| get_children: impl Fn(StatementIdx) -> Result<Vec<StatementIdx>, E>, | ||
| out_of_bounds_err: impl Fn(StatementIdx) -> E, | ||
| cycle_err: impl Fn(StatementIdx) -> E, | ||
| ) -> Result<Vec<StatementIdx>, E> { | ||
| let mut ordering = vec![]; | ||
| let mut status = vec![TopologicalOrderStatus::NotStarted; node_count]; | ||
| for root in roots { | ||
| calculate_topological_ordering( | ||
| detect_cycles, | ||
| &mut ordering, | ||
| &mut status, | ||
| root, | ||
| &get_children, | ||
| &out_of_bounds_err, | ||
| &cycle_err, | ||
| )?; | ||
| } | ||
| Ok(ordering) | ||
| } | ||
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| /// Calculates the topological ordering starting from `root`. For more info see | ||
| /// `get_topological_ordering`. | ||
| fn calculate_topological_ordering<E>( | ||
| detect_cycles: bool, | ||
| ordering: &mut Vec<StatementIdx>, | ||
| status: &mut [TopologicalOrderStatus], | ||
| root: StatementIdx, | ||
| get_children: &impl Fn(StatementIdx) -> Result<Vec<StatementIdx>, E>, | ||
| out_of_bounds_err: &impl Fn(StatementIdx) -> E, | ||
| cycle_err: &impl Fn(StatementIdx) -> E, | ||
| ) -> Result<(), E> { | ||
| // A stack of statements to visit. | ||
| // When the pair is popped out of the stack, `is_done=true` means that we've already visited | ||
| // all of its children, and we just need to add it to the ordering. | ||
| let mut stack = vec![root]; | ||
|
|
||
| while let Some(idx) = stack.pop() { | ||
| match status.get(idx.0) { | ||
| Some(TopologicalOrderStatus::NotStarted) => { | ||
| // Mark the statement as `InProgress`. | ||
| status[idx.0] = TopologicalOrderStatus::InProgress; | ||
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| // Push the statement back to the stack, so that after visiting all | ||
| // of its children, we would add it to the ordering. | ||
| // Add the missing children on top of it. | ||
| stack.push(idx); | ||
| for child in get_children(idx)? { | ||
| match status.get(child.0) { | ||
| Some(TopologicalOrderStatus::InProgress) => { | ||
| if detect_cycles { | ||
| return Err(cycle_err(child)); | ||
| } | ||
| continue; | ||
| } | ||
| Some(TopologicalOrderStatus::Done) => { | ||
| continue; | ||
| } | ||
| Some(TopologicalOrderStatus::NotStarted) => { | ||
| stack.push(child); | ||
| } | ||
| None => { | ||
| return Err(out_of_bounds_err(child)); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| Some(TopologicalOrderStatus::InProgress) => { | ||
| // Mark the statement as `Done`. | ||
| status[idx.0] = TopologicalOrderStatus::Done; | ||
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| // Add the element to the ordering after visiting all its children. | ||
| // This gives us reverse topological ordering. | ||
| ordering.push(idx); | ||
| } | ||
| Some(TopologicalOrderStatus::Done) => { | ||
| // Do nothing. | ||
| } | ||
| None => { | ||
| return Err(out_of_bounds_err(idx)); | ||
| } | ||
| } | ||
| } | ||
|
|
||
| Ok(()) | ||
| } |
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