feat!: do not require an Order edge for each nonlocal `Ext` edge; compute on demand in scheduling_graph() by acl-cqc · Pull Request #2951 · Quantinuum/hugr

acl-cqc · 2026-03-16T16:57:54Z

Removes validation check that order edges are present (for each nonlocal)
Removes rust+python builder code that adds order edges (for each nonlocal)
Actually calculates the edges required and adds them to SynEdgeWrapper
Updates the SiblingSubgraph test from refactor: add HugrView::scheduling_graph, deprecate region_portgraph #3015 to show the changes in behaviour
Updates spec
Removes many APIs deprecated in refactor: add HugrView::scheduling_graph, deprecate region_portgraph #3015

BREAKING CHANGE: Hugrs are no longer guaranteed to have an Order edge representing the ordering constraint from each nonlocal Ext edge; require HugrView impls to provide scheduling_graph; remove deprecated region_portgraph(), as_petgraph(), into_region_portgraph(), sibling_subgraph::{TopoConvexChecker, ValidationMode, SiblingSubgraph::validate(), ConvexChecker}, ValidationError::MissingOrderEdge

…Topo

…woot!)

…Graph

codecov · 2026-04-05T11:34:11Z

Codecov Report

❌ Patch coverage is 98.03922% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.15%. Comparing base (d6e11c8) to head (09f6d3e).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
hugr-persistent/src/parents_view.rs	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2951      +/-   ##
==========================================
+ Coverage   81.07%   81.15%   +0.07%     
==========================================
  Files         242      240       -2     
  Lines       45183    44954     -229     
  Branches    38951    38724     -227     
==========================================
- Hits        36633    36483     -150     
+ Misses       6585     6497      -88     
- Partials     1965     1974       +9

Flag	Coverage Δ
python	`88.86% <ø> (-0.04%)`	⬇️
rust	`79.91% <98.03%> (+0.09%)`	⬆️

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…able

…ortgraph left

This reverts commit 04178e4.

…Wrapper

hugrbot · 2026-05-05T11:22:41Z

This PR contains breaking changes to the public Rust API.

cargo-semver-checks summary

    Building hugr v0.27.1 (current)
     Built [  33.490s] (current)
   Parsing hugr v0.27.1 (current)
    Parsed [   0.004s] (current)
  Building hugr v0.27.1 (baseline)
     Built [  33.827s] (baseline)
   Parsing hugr v0.27.1 (baseline)
    Parsed [   0.004s] (baseline)
  Checking hugr v0.27.1 -> v0.27.1 (assume minor change)
   Checked [   0.011s] 196 checks: 196 pass, 56 skip
   Summary no semver update required
  Finished [  68.785s] hugr
  Building hugr-cli v0.27.1 (current)
     Built [  27.529s] (current)
   Parsing hugr-cli v0.27.1 (current)
    Parsed [   0.006s] (current)
  Building hugr-cli v0.27.1 (baseline)
     Built [  27.558s] (baseline)
   Parsing hugr-cli v0.27.1 (baseline)
    Parsed [   0.006s] (baseline)
  Checking hugr-cli v0.27.1 -> v0.27.1 (assume minor change)
   Checked [   0.015s] 196 checks: 196 pass, 56 skip
   Summary no semver update required
  Finished [  56.729s] hugr-cli
  Building hugr-core v0.27.1 (current)
     Built [  24.114s] (current)
   Parsing hugr-core v0.27.1 (current)
    Parsed [   0.085s] (current)
  Building hugr-core v0.27.1 (baseline)
     Built [  23.996s] (baseline)
   Parsing hugr-core v0.27.1 (baseline)
    Parsed [   0.081s] (baseline)
  Checking hugr-core v0.27.1 -> v0.27.1 (assume minor change)
   Checked [   0.214s] 196 checks: 189 pass, 7 fail, 0 warn, 56 skip

--- failure enum_missing: pub enum removed or renamed ---

Description:
A publicly-visible enum cannot be imported by its prior path. A `pub use` may have been removed, or the enum itself may have been renamed or removed entirely.
      ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
     impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.47.0/src/lints/enum_missing.ron

Failed in:
enum hugr_core::hugr::views::sibling_subgraph::ValidationMode, previously in file /home/runner/work/hugr/hugr/BASELINE_BRANCH/hugr-core/src/hugr/views/sibling_subgraph.rs:839

--- failure enum_no_repr_variant_discriminant_changed: enum variant had its discriminant change value ---

Description:
The enum's variant had its discriminant value change. This breaks downstream code that used its value via a numeric cast like `as isize`.
      ref: https://doc.rust-lang.org/reference/items/enumerations.html#assigning-discriminant-values
     impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.47.0/src/lints/enum_no_repr_variant_discriminant_changed.ron

Failed in:
variant InterGraphEdgeError::NoRelation 3 -> 2 in /home/runner/work/hugr/hugr/PR_BRANCH/hugr-core/src/hugr/validate.rs:800
variant InterGraphEdgeError::NonDominatedAncestor 4 -> 3 in /home/runner/work/hugr/hugr/PR_BRANCH/hugr-core/src/hugr/validate.rs:810

--- failure enum_variant_missing: pub enum variant removed or renamed ---

Description:
A publicly-visible enum has at least one variant that is no longer available under its prior name. It may have been renamed or removed entirely.
      ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
     impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.47.0/src/lints/enum_variant_missing.ron

Failed in:
variant InterGraphEdgeError::MissingOrderEdge, previously in file /home/runner/work/hugr/hugr/BASELINE_BRANCH/hugr-core/src/hugr/validate.rs:813

--- failure inherent_method_missing: pub method removed or renamed ---

Description:
A publicly-visible method or associated fn is no longer available under its prior name. It may have been renamed or removed entirely.
      ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
     impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.47.0/src/lints/inherent_method_missing.ron

Failed in:
SiblingSubgraph::validate, previously in file /home/runner/work/hugr/hugr/BASELINE_BRANCH/hugr-core/src/hugr/views/sibling_subgraph.rs:527
SiblingSubgraph::validate, previously in file /home/runner/work/hugr/hugr/BASELINE_BRANCH/hugr-core/src/hugr/views/sibling_subgraph.rs:527
Hugr::into_region_portgraph, previously in file /home/runner/work/hugr/hugr/BASELINE_BRANCH/hugr-core/src/hugr/internal.rs:401
Hugr::into_region_portgraph, previously in file /home/runner/work/hugr/hugr/BASELINE_BRANCH/hugr-core/src/hugr/internal.rs:401

--- failure module_missing: pub module removed or renamed ---

Description:
A publicly-visible module cannot be imported by its prior path. A `pub use` may have been removed, or the module may have been renamed, removed, or made non-public.
      ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
     impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.47.0/src/lints/module_missing.ron

Failed in:
mod hugr_core::hugr::views::petgraph, previously in file /home/runner/work/hugr/hugr/BASELINE_BRANCH/hugr-core/src/hugr/views/petgraph.rs:1

--- failure struct_missing: pub struct removed or renamed ---

Description:
A publicly-visible struct cannot be imported by its prior path. A `pub use` may have been removed, or the struct itself may have been renamed or removed entirely.
      ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
     impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.47.0/src/lints/struct_missing.ron

Failed in:
struct hugr_core::hugr::views::petgraph::HugrNodeRef, previously in file /home/runner/work/hugr/hugr/BASELINE_BRANCH/hugr-core/src/hugr/views/petgraph.rs:190
struct hugr_core::hugr::views::sibling_subgraph::ConvexChecker, previously in file /home/runner/work/hugr/hugr/BASELINE_BRANCH/hugr-core/src/hugr/views/sibling_subgraph.rs:1090
struct hugr_core::hugr::views::petgraph::PetgraphWrapper, previously in file /home/runner/work/hugr/hugr/BASELINE_BRANCH/hugr-core/src/hugr/views/petgraph.rs:16
struct hugr_core::hugr::views::PetgraphWrapper, previously in file /home/runner/work/hugr/hugr/BASELINE_BRANCH/hugr-core/src/hugr/views/petgraph.rs:16

--- failure trait_method_missing: pub trait method removed or renamed ---

Description:
A trait method is no longer callable, and may have been renamed or removed entirely.
      ref: https://doc.rust-lang.org/cargo/reference/semver.html#trait-item-signature
     impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.47.0/src/lints/trait_method_missing.ron

Failed in:
method as_petgraph of trait HugrView, previously in file /home/runner/work/hugr/hugr/BASELINE_BRANCH/hugr-core/src/hugr/views.rs:397
method as_petgraph of trait HugrView, previously in file /home/runner/work/hugr/hugr/BASELINE_BRANCH/hugr-core/src/hugr/views.rs:397
method as_petgraph of trait HugrView, previously in file /home/runner/work/hugr/hugr/BASELINE_BRANCH/hugr-core/src/hugr/views.rs:397
method region_portgraph of trait HugrInternals, previously in file /home/runner/work/hugr/hugr/BASELINE_BRANCH/hugr-core/src/hugr/internal.rs:47

   Summary semver requires new major version: 7 major and 0 minor checks failed
  Finished [  49.279s] hugr-core
  Building hugr-llvm v0.27.1 (current)
     Built [  28.157s] (current)
   Parsing hugr-llvm v0.27.1 (current)
    Parsed [   0.012s] (current)
  Building hugr-llvm v0.27.1 (baseline)
     Built [  28.345s] (baseline)
   Parsing hugr-llvm v0.27.1 (baseline)
    Parsed [   0.012s] (baseline)
  Checking hugr-llvm v0.27.1 -> v0.27.1 (assume minor change)
   Checked [   0.044s] 196 checks: 196 pass, 56 skip
   Summary no semver update required
  Finished [  57.774s] hugr-llvm
  Building hugr-model v0.27.1 (current)
     Built [  10.221s] (current)
   Parsing hugr-model v0.27.1 (current)
    Parsed [   0.016s] (current)
  Building hugr-model v0.27.1 (baseline)
     Built [  10.222s] (baseline)
   Parsing hugr-model v0.27.1 (baseline)
    Parsed [   0.016s] (baseline)
  Checking hugr-model v0.27.1 -> v0.27.1 (assume minor change)
   Checked [   0.029s] 196 checks: 196 pass, 56 skip
   Summary no semver update required
  Finished [  21.282s] hugr-model
  Building hugr-persistent v0.6.1 (current)
     Built [  20.992s] (current)
   Parsing hugr-persistent v0.6.1 (current)
    Parsed [   0.008s] (current)
  Building hugr-persistent v0.6.1 (baseline)
     Built [  21.276s] (baseline)
   Parsing hugr-persistent v0.6.1 (baseline)
    Parsed [   0.007s] (baseline)
  Checking hugr-persistent v0.6.1 -> v0.6.1 (assume minor change)
   Checked [   0.012s] 196 checks: 196 pass, 56 skip
   Summary no semver update required
  Finished [  43.025s] hugr-persistent

acl-cqc · 2026-05-05T13:18:37Z

+/// The API is designed for `hugr-persistent` and allows to implement [HugrView] such that
+/// [HugrInternals::RegionPortgraph] is not tied to the original view but rather an owned
+/// temporary [Hugr].
+pub fn owned_scheduling_graph<'a, N: HugrNode, V>(


This is broadly equivalent to the removed Hugr::into_region_portgraph from internals.rs; it could be an instance method again (into_scheduling_graph) but seems more consistent in this file.

It is definitely the part of the PR that I'm least keen on!! But either we expose more internal details of SchedulingGraph (which I've been trying to avoid in the design, to keep some flexibility to change in the future), and use those details in hugr-persistent; or, we put some hugr-persistent-specific functionality here. This PR chooses the latter route...
(but it doesn't seem that weird a functionality, even if hugr-persistent is the only place we're using it ATM.)

Thoughts welcome!

acl-cqc · 2026-05-05T13:20:01Z

+respecting the Dataflow edges.** The following operations are used to
 express control flow, i.e. conditional or repeated evaluation.

+**ALAN this might be a place to either say, and respecting the ordering


Thoughts here?

Yes, could be worth saying that descendent nodes may be interleaved with siblings, subject to the ordering constraints imposed by Dataflow edges.

I have done - I realize that I was actually planning for that to come later along with tweaks to some Hugr code to enact it, but it's not a correction to the spec (it doesn't change anything that was there before AFAICS), merely a clarification; and whilst there is some Hugr code that sort-of-assumes otherwise, I think updating that can be classed as an improvement or optimization (or just possibly bugfix) i.e. in another PR.

So, would you mind having another quick look over the spec 🙏 ? I also explicitly mentioned respecting Order edges too (but not synthetic/nonlocal edges since there is no need to).

(@cqc-alec, sorry!)

cqc-alec · 2026-05-05T13:31:36Z


 def test_build_inter_graph(snapshot):
+    # Possibly a bit redundant now, really we're just testing that we *don't* do
+    # anything special anymore, following https://github.com/Quantinuum/hugr/pulls/2951.


Suggested change

# anything special anymore, following https://github.com/Quantinuum/hugr/pulls/2951.

# anything special anymore, following https://github.com/Quantinuum/hugr/pull/2951.

I am humbled. I would never have spotted that myself :-)

cqc-alec · 2026-05-05T13:56:13Z

+respecting the Dataflow edges.** The following operations are used to
 express control flow, i.e. conditional or repeated evaluation.

+**ALAN this might be a place to either say, and respecting the ordering


Yes, could be worth saying that descendent nodes may be interleaved with siblings, subject to the ordering constraints imposed by Dataflow edges.

cqc-alec

LGTM

acl-cqc added 11 commits March 31, 2026 18:10

Add (local to views) mod syn_edge with SynEdgeWrapper

e010488

Remove commented-out GetAdjacencyMatrix

69eea12

Move SiblingSubgraph tests into new file

b9f83a5

add petgraph convexity checker

12a3fd5

Define scheduling_graph in HugrView

3fcbbdc

Add small test that implements expected traits

4d1d0c8

SchedulingGraph: rename node(s=>_map), add fn graph() -> impl... for …

b813360

…Topo

Deprecate region_portgraph, switch all uses except sibling_subgraph (…

87f0c36

…woot!)

Fix TopoConvexChecker where, add test that we can use on Scheduling…

d532d3c

…Graph

WIP add SchedGraphChecker and try to impl HugrConvexChecker for it

514e23e

WIP2 any closer?

d767be2

acl-cqc added this to the hugr-rs 0.28.0 milestone Apr 2, 2026

acl-cqc mentioned this pull request Apr 2, 2026

refactor: add HugrView::scheduling_graph, deprecate region_portgraph #3015

Merged

acl-cqc force-pushed the acl/syn_edges branch from ac077b4 to 7f5b10a Compare April 5, 2026 11:30

acl-cqc changed the base branch from main to acl/syn_edge_prep April 5, 2026 11:31

acl-cqc added 8 commits April 9, 2026 09:46

Reimplement petgraph traits conditioning on T: LinkView, except Visit…

fbc676e

…able

More tests of what compiles

04178e4

fix sibling_subgraph??

3818cfe

and generalize TopoConvexChecker

9cf4da8

Deprecate stuff in sibling_subgraph, move over...some tricky region_p…

242193e

…ortgraph left

update tests to avoid deprecation

ff2e0cc

Revert "More tests of what compiles"

ae1bf67

This reverts commit 04178e4.

Rename SchedulingGraph::graph -> ::petgraph

521319f

acl-cqc force-pushed the acl/syn_edge_prep branch from 6db3845 to 521319f Compare April 9, 2026 08:49

acl-cqc added 5 commits April 9, 2026 09:53

better-backdoors

aadc6b2

syn_edge.rs module comment + remove compilation tests

4137aff

sib_sub: ConvexChecker deprecation should name PortgraphCheckerWithNodes

7525ac4

clippy hugr-persistent

e1b6fca

doc fix and doc workaround

db89b21

acl-cqc added 4 commits April 29, 2026 13:04

drop the assert that there are no syn edges to be dropped

63b308c

"correct" test assertions i.e. changes in behaviour

9a79f46

Update python builder too

24c5baf

Remove region_portgraph, into_region_portgraph, as_petgraph, Petgraph…

a173c2d

…Wrapper

acl-cqc force-pushed the acl/syn_edges branch from aa5272d to a173c2d Compare April 29, 2026 12:06

acl-cqc added 4 commits April 29, 2026 13:52

fmt

52a9dd9

correct node_count -> capacity

a210440

allow not expect deprecated works w/out mod hidden

16bbe5f

Merge remote-tracking branch 'origin/main' into acl/syn_edge_prep

ea9f210

Base automatically changed from acl/syn_edge_prep to main May 5, 2026 09:50

acl-cqc added 3 commits May 5, 2026 11:19

Merge remote-tracking branch 'origin/main' into acl/syn_edge_prep

5d235f9

Merge branch 'acl/syn_edge_prep' into acl/syn_edges

199cc24

Remove deprecated SiblingSubgraph stuff too

b11ef50

acl-cqc changed the title ~~feat!: do not require an Order edge for each nonlocal Ext edge; order_graph computes on demand~~ feat!: do not require an Order edge for each nonlocal Ext edge; compute on demand in scheduling_graph() May 5, 2026

rename hugr-persistent unused variables

9df8c1d

acl-cqc added 3 commits May 5, 2026 12:27

Update docs re. deprecation (oops remove one missed from #3051)

64c3bef

snapshot-update

b8a8108

fix hugr-persistent, oops - add pub fn owned_scheduling_graph in hugr

fcad20b

acl-cqc marked this pull request as ready for review May 5, 2026 13:09

acl-cqc requested a review from a team as a code owner May 5, 2026 13:09

acl-cqc requested review from cqc-alec and mark-koch and removed request for mark-koch May 5, 2026 13:09

acl-cqc commented May 5, 2026

View reviewed changes

cqc-alec approved these changes May 5, 2026

View reviewed changes

acl-cqc added 2 commits May 6, 2026 15:51

review comments, updating spec

5f7fd80

wordwrap, and driveby backquote Conditional

09f6d3e

cqc-alec approved these changes May 7, 2026

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feat!: do not require an Order edge for each nonlocal `Ext` edge; compute on demand in scheduling_graph()#2951

feat!: do not require an Order edge for each nonlocal `Ext` edge; compute on demand in scheduling_graph()#2951
acl-cqc wants to merge 53 commits intomainfrom
acl/syn_edges

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	# anything special anymore, following https://github.com/Quantinuum/hugr/pulls/2951.
	# anything special anymore, following https://github.com/Quantinuum/hugr/pull/2951.

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acl-cqc commented Mar 16, 2026 •

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