fix: more nondeterminism in linking by acl-cqc · Pull Request #2792 · Quantinuum/hugr

acl-cqc · 2026-01-05T17:55:08Z

More iteration through HashMaps keyed by source node i.e. adding source functions to the target in a different order...

acl-cqc · 2026-01-05T18:04:46Z

hugr-core/src/hugr/linking.rs

-                    NodeLinkingDirective::UseExisting(_) => Either::Right(std::iter::once(ch)),
-                }));
-        let mut roots = HashMap::new();
+        // Make a fresh map here, so determinism is not affected by iteration order of the HashMap in `children`


This is a bit unfortunate, but NodeLinkingDirectives is a public type alias of HashMap so it would be breaking to change it, and it already gets iterated through twice so a third time can't be that bad can it? 🔥 🩹

Happy to open an issue or PR to fix in a later breaking release if anyone feels strongly

I think open an issue, label as "perf" and leave a comment (to aid a future profiler)

codecov · 2026-01-05T18:05:31Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.70%. Comparing base (191c473) to head (1f7dc58).
⚠️ Report is 7 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2792   +/-   ##
=======================================
  Coverage   83.69%   83.70%           
=======================================
  Files         261      261           
  Lines       52561    52581   +20     
  Branches    47307    47327   +20     
=======================================
+ Hits        43991    44011   +20     
  Misses       6183     6183           
  Partials     2387     2387

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rust	`83.13% <100.00%> (+<0.01%)`	⬆️

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acl-cqc · 2026-01-06T11:04:30Z

hugr-core/src/hugr/linking.rs

+        // Really this just checks that things from the source hugr are added in consistent
+        // order (taking next available indices in the target). Actually linking them with
+        // nodes already (at consistent positions) in the target only reduces variability.
+        let (insert, _, _) = dfg_calling_defn_decl();


This was a handy hugr lying around, with the entrypoint + two defns/decls being inserted as separate "trees" in a forest, there are 3!=6 possible orderings, so the test succeeded around 1 time in 6. We could decrease the odds of a false positive by inserting a bigger Hugr but it would make a longer test.

ss2165 · 2026-01-06T14:27:09Z

hugr-core/src/hugr/linking.rs

-                    NodeLinkingDirective::UseExisting(_) => Either::Right(std::iter::once(ch)),
-                }));
-        let mut roots = HashMap::new();
+        // Make a fresh map here, so determinism is not affected by iteration order of the HashMap in `children`


I think open an issue, label as "perf" and leave a comment (to aid a future profiler)

## 🤖 New release * `hugr-model`: 0.25.2 -> 0.25.3 (✓ API compatible changes) * `hugr-core`: 0.25.2 -> 0.25.3 (✓ API compatible changes) * `hugr-llvm`: 0.25.2 -> 0.25.3 (✓ API compatible changes) * `hugr-passes`: 0.25.2 -> 0.25.3 (✓ API compatible changes) * `hugr-persistent`: 0.4.2 -> 0.4.3 (✓ API compatible changes) * `hugr`: 0.25.2 -> 0.25.3 (✓ API compatible changes) * `hugr-cli`: 0.25.2 -> 0.25.3 (✓ API compatible changes) <details><summary>Changelog</summary> ## `hugr-model` <blockquote> ## [0.25.0](hugr-model-v0.24.3...hugr-model-v0.25.0) - 2025-12-22 ### Bug Fixes - *(model)* avoid non abi-compatible pyo3 calls ([#2679](#2679)) ### New Features - [**breaking**] Upgrade pyo3 dependency to 0.27 ([#2736](#2736)) ### Refactor - Direct import of model representation to Python ([#2683](#2683)) </blockquote> ## `hugr-core` <blockquote> ## [0.25.3](hugr-core-v0.25.2...hugr-core-v0.25.3) - 2026-01-09 ### Bug Fixes - more nondeterminism in linking ([#2792](#2792)) ### Documentation - Add collection extension ops to the spec ([#2767](#2767)) </blockquote> ## `hugr-llvm` <blockquote> ## [0.25.0](hugr-llvm-v0.24.3...hugr-llvm-v0.25.0) - 2025-12-22 ### New Features - *(llvm)* [**breaking**] upgrade to inkwell 0.7 ([#2695](#2695)) ### Refactor - Deprecate Value::Function and inline_constant_functions ([#2770](#2770)) </blockquote> ## `hugr-passes` <blockquote> ## [0.25.3](hugr-passes-v0.25.2...hugr-passes-v0.25.3) - 2026-01-09 ### Bug Fixes - *(hugr-passes)* Recursive replacement on NodeTemplate::LinkedHugr ([#2800](#2800)) ### Refactor - *(ReplaceTypes)* [tiny] correct computation of containing_func ([#2807](#2807)) </blockquote> ## `hugr-persistent` <blockquote> ## [0.4.0](hugr-persistent-v0.3.4...hugr-persistent-v0.4.0) - 2025-12-22 ### New Features - [**breaking**] Remove `RootCheckable` ([#2704](#2704)) - [**breaking**] Bump MSRV to Rust 1.89 ([#2747](#2747)) - [**breaking**] Type-safe access for node metadata ([#2755](#2755)) ### Refactor - [**breaking**] Remove multiple deprecated definitions ([#2751](#2751)) </blockquote> ## `hugr` <blockquote> ## [0.25.3](hugr-v0.25.2...hugr-v0.25.3) - 2026-01-09 ### Bug Fixes - *(hugr-passes)* Recursive replacement on NodeTemplate::LinkedHugr ([#2800](#2800)) - more nondeterminism in linking ([#2792](#2792)) ### Documentation - Add collection extension ops to the spec ([#2767](#2767)) ### Refactor - *(ReplaceTypes)* [tiny] correct computation of containing_func ([#2807](#2807)) </blockquote> ## `hugr-cli` <blockquote> ## [0.25.0](hugr-cli-v0.24.3...hugr-cli-v0.25.0) - 2025-12-22 ### New Features - *(cli, python)* programmatic interface to cli with python bindings ([#2677](#2677)) - return description output to python on error ([#2681](#2681)) - [**breaking**] Type-safe access for node metadata ([#2755](#2755)) - [**breaking**] GeneratorDesc metadata definition ([#2759](#2759)) ### Refactor - [**breaking**] move envelope reading to dedicated module with dedicated errors ([#2689](#2689)) - *(cli)* [**breaking**] remove deprecated hugr_json handling ([#2690](#2690)) - [**breaking**] Remove multiple deprecated definitions ([#2751](#2751)) </blockquote> </details> --- This PR was generated with [release-plz](https://github.com/release-plz/release-plz/).

## 🤖 New release * `hugr-model`: 0.25.3 -> 0.25.4 (✓ API compatible changes) * `hugr-core`: 0.25.3 -> 0.25.4 (✓ API compatible changes) * `hugr-llvm`: 0.25.3 -> 0.25.4 (✓ API compatible changes) * `hugr-passes`: 0.25.3 -> 0.25.4 (✓ API compatible changes) * `hugr`: 0.25.3 -> 0.25.4 (✓ API compatible changes) * `hugr-cli`: 0.25.3 -> 0.25.4 (✓ API compatible changes) * `hugr-persistent`: 0.4.3 -> 0.4.4 <details><summary>Changelog</summary> ## `hugr-model` <blockquote> ## [0.25.0](hugr-model-v0.24.3...hugr-model-v0.25.0) - 2025-12-22 ### Bug Fixes - *(model)* avoid non abi-compatible pyo3 calls ([#2679](#2679)) ### New Features - [**breaking**] Upgrade pyo3 dependency to 0.27 ([#2736](#2736)) ### Refactor - Direct import of model representation to Python ([#2683](#2683)) </blockquote> ## `hugr-core` <blockquote> ## [0.25.3](hugr-core-v0.25.2...hugr-core-v0.25.3) - 2026-01-09 ### Bug Fixes - more nondeterminism in linking ([#2792](#2792)) ### Documentation - Add collection extension ops to the spec ([#2767](#2767)) </blockquote> ## `hugr-llvm` <blockquote> ## [0.25.0](hugr-llvm-v0.24.3...hugr-llvm-v0.25.0) - 2025-12-22 ### New Features - *(llvm)* [**breaking**] upgrade to inkwell 0.7 ([#2695](#2695)) ### Refactor - Deprecate Value::Function and inline_constant_functions ([#2770](#2770)) </blockquote> ## `hugr-passes` <blockquote> ## [0.25.4](hugr-passes-v0.25.3...hugr-passes-v0.25.4) - 2026-01-14 ### Bug Fixes - UnpackTuple error on disconnected outputs ([#2813](#2813)) </blockquote> ## `hugr` <blockquote> ## [0.25.4](hugr-v0.25.3...hugr-v0.25.4) - 2026-01-14 ### Bug Fixes - UnpackTuple error on disconnected outputs ([#2813](#2813)) </blockquote> ## `hugr-cli` <blockquote> ## [0.25.0](hugr-cli-v0.24.3...hugr-cli-v0.25.0) - 2025-12-22 ### New Features - *(cli, python)* programmatic interface to cli with python bindings ([#2677](#2677)) - return description output to python on error ([#2681](#2681)) - [**breaking**] Type-safe access for node metadata ([#2755](#2755)) - [**breaking**] GeneratorDesc metadata definition ([#2759](#2759)) ### Refactor - [**breaking**] move envelope reading to dedicated module with dedicated errors ([#2689](#2689)) - *(cli)* [**breaking**] remove deprecated hugr_json handling ([#2690](#2690)) - [**breaking**] Remove multiple deprecated definitions ([#2751](#2751)) </blockquote> ## `hugr-persistent` <blockquote> ## [0.4.0](hugr-persistent-v0.3.4...hugr-persistent-v0.4.0) - 2025-12-22 ### New Features - [**breaking**] Remove `RootCheckable` ([#2704](#2704)) - [**breaking**] Bump MSRV to Rust 1.89 ([#2747](#2747)) - [**breaking**] Type-safe access for node metadata ([#2755](#2755)) ### Refactor - [**breaking**] Remove multiple deprecated definitions ([#2751](#2751)) </blockquote> </details> --- This PR was generated with [release-plz](https://github.com/release-plz/release-plz/).

acl-cqc added 6 commits January 5, 2026 17:49

test

8724c1f

make test pass

61673cd

driveby sig update to use alias

a7fbbde

test link_from_view

d817412

Also fix insert_link_from_view

939f043

fmt

475ea3d

acl-cqc commented Jan 5, 2026

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acl-cqc mentioned this pull request Jan 5, 2026

feat: hide new public funcs introduced by linearization Quantinuum/tket2#1333

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acl-cqc marked this pull request as ready for review January 5, 2026 18:09

acl-cqc requested a review from a team as a code owner January 5, 2026 18:09

acl-cqc requested a review from ss2165 January 5, 2026 18:09

acl-cqc commented Jan 6, 2026

View reviewed changes

ss2165 approved these changes Jan 6, 2026

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may be slow comment

1f7dc58

acl-cqc enabled auto-merge January 6, 2026 15:53

acl-cqc added this pull request to the merge queue Jan 6, 2026

Merged via the queue into main with commit 370dbc2 Jan 6, 2026
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acl-cqc deleted the acl/linking_determinism branch January 6, 2026 16:03

hugrbot mentioned this pull request Jan 6, 2026

chore: release #2798

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acl-cqc mentioned this pull request Jan 6, 2026

Copying Map in insert_view_link_by_node #2801

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hugrbot mentioned this pull request Jan 13, 2026

chore: release #2812

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hugrbot mentioned this pull request Jan 15, 2026

chore: release #2815

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fix: more nondeterminism in linking#2792

fix: more nondeterminism in linking#2792
acl-cqc merged 7 commits intomainfrom
acl/linking_determinism

acl-cqc commented Jan 5, 2026

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