This is a proposal to decouple navigation from stepping by

changing the navigator interface to only consume its state and not the propagation state
providing position and direction as an input to the navigation
putting the Propagator in charge of communicating the target and estimated distance to the stepper

Originally I wanted the navigator to return the next step size but that clashes with the multi stepper. The current solution allows the stepper to judge on the step size given a surface. This allows the stepper to tweak the step size or to just take what the navigator proposed. In case of the multi stepper we will still just run intersections with the individual components.

The navigator is reduced to providing surface candidates and the surface status will be purely determined by the stepper. The propagator passes the information so the navigator knows when to switch surface / layer / volume.

Ultimately this removes all the templating from the navigator and the interface captures well what the navigator is supposed to do by having dedicated and visible I/O paths.

I only did this for Navigator, VoidNavigator, DirectNavigator for now to show case the changes and to see how this performs.

In case this is where we want to go I would like to do something similar to the steppers.

Jul 27 '24 20:07 andiwand

📊: Physics performance monitoring for 1288d9ff725d1a71d345066eb3d1a5cd6e3356ef

Full contents

physmon summary

Jul 28 '24 11:07 github-actions[bot]

The current version avoids double intersection while approaching the target which result in CPU performance improvements. Interestingly this is only pronounced for Fatras and quite suppressed for the CKF

Aug 21 '24 14:08 andiwand

Quality Gate passed

Issues
20 New issues
0 Accepted issues

Measures
0 Security Hotspots
49.4% Coverage on New Code
0.6% Duplication on New Code

See analysis details on SonarCloud

Aug 21 '24 21:08 sonarqubecloud[bot]

Walkthrough

Significant changes to navigation and propagation systems in ACTS, there are. Restructuring of navigator classes, method signatures, and state management, we observe. Removal of redundant variables, addition of new methods for target resolution, and streamlining of initialization processes, the modifications encompass. A comprehensive refactoring of navigation logic across multiple components, this represents.

Changes

File	Change Summary
`Core/include/Acts/Navigation/...`	Navigator classes updated with new initialization, state management, and target resolution methods
`Core/include/Acts/Propagator/...`	Stepper and navigator interfaces modified, new `NavigationTarget` struct introduced
`Core/src/Propagator/...`	Error handling and category updates to reflect new navigation logic
`Tests/...`	Test cases adjusted to align with new navigation and propagation interfaces

Possibly related PRs

#3986: The changes in this PR involve modifications to the DetectorNavigator class, specifically in the handling of step sizes and surface status updates, which are relevant to the changes made in the DetectorNavigator class in the main PR.
#3987: This PR refactors the AtlasStepper class, including changes to the State struct and its initialization, which aligns with the modifications made to the State struct in the main PR.
#3984: The removal of the NavigationBreakAborter and its associated functionality in this PR simplifies the actor list, which may relate to the overall navigation logic being streamlined in the main PR.

Suggested Labels

automerge

Suggested Reviewers

paulgessinger

Poem

Navigators dance, steppers glide,
Through volumes vast, with physics pride.
Targets found, paths refined,
ACTS refactors, code intertwined! 🚀🧭

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Nov 16 '24 10:11 coderabbitai[bot]

Probably makes my life easier implementing a Gen3 navigator

Nov 16 '24 11:11 paulgessinger

:white_check_mark: Athena integration test results [f060123b034411791d6c94a419acb2799f85297a]

:white_check_mark: All tests successful

status	job	report
:green_circle:	report_pull_request
:green_circle:	run_workflow_tests_run4_mc
:green_circle:	run_workflow_tests_run2_mc
:green_circle:	run_workflow_tests_run2_data
:green_circle:	run_workflow_tests_run3_mc
:green_circle:	run_workflow_tests_run3_data
:green_circle:	test_ActsDumpGeometryIdentifiers
:green_circle:	test_ActsCheckObjectCountsWorkflowHgtd
:green_circle:	test_ActsCheckObjectCountsCachedWorkflow
:green_circle:	test_ActsCheckObjectCountsWorkflow
:green_circle:	test_ActsEFTrackFit
:green_circle:	test_ActsPersistifySeeds
:green_circle:	test_ActsBenchmarkWithSpot
:green_circle:	test_ActsAnalogueClustering
:green_circle:	test_ActsWorkflowHeavyIons
:green_circle:	test_ActsWorkflowFastTracking
:green_circle:	test_ActsWorkflowCached
:green_circle:	test_ActsWorkflow
:green_circle:	test_ActsValidateAmbiguityResolution
:green_circle:	test_ActsValidateResolvedTracks
:green_circle:	test_ActsValidateTracks
:green_circle:	test_ActsValidateActsCoreSpacePoints
:green_circle:	test_ActsValidateActsSpacePoints
:green_circle:	test_ActsValidateSeeds
:green_circle:	test_ActsValidateOrthogonalSeeds
:green_circle:	test_ActsValidateClusters
:green_circle:	test_ActsPersistifyEDM
:green_circle:	test_ActsGx2fRefitting
:green_circle:	test_ActsGSFRefitting
:green_circle:	test_ActsKfRefitting
:green_circle:	test_ActsExtrapolationAlgTest
:green_circle:	test_ActsITkTest

Nov 25 '24 20:11 acts-project-service

After discussion with @andiwand:

Change the -1 sentinel int to an std::optional<std::size_t>
Stage::noTarget -> Stage::initial
Disambiguate NavigationTarget::invalid and checkTargetValid: valid does not mean the same thing currently.

Dec 13 '24 09:12 paulgessinger

The stepper options changes escalated a bit and I failed to put this in a different commit. The changes could be factorized into the following

[x] GSF actor / aborter https://github.com/acts-project/acts/pull/3984
[x] Stepper update signature and constrained step rename https://github.com/acts-project/acts/pull/3986
[x] Stepper option handling https://github.com/acts-project/acts/pull/3987
[x] CKF / KF path length aborter https://github.com/acts-project/acts/pull/3985
[x] Actual navigator refactor https://github.com/acts-project/acts/pull/3449

Dec 13 '24 14:12 andiwand

Add navigator concept

Dec 14 '24 14:12 andiwand

GSF is producing some new errors after this change https://github.com/acts-project/acts/actions/runs/12711434053/job/35435102207?pr=3449

needs some investigation

Jan 10 '25 15:01 andiwand

With https://github.com/acts-project/acts/pull/3449/commits/cf2b28aa8f0cec124833d3b2184cca6fe367fd22 I am trying to work around an FPE that popped up in the GSF.

We already checked for std::isfinite which might come from a previous treatment of the FPE without monitoring. So I thought I can just prevent it by checking directly on detR.

What do you think about that handling @benjaminhuth @paulgessinger?

Jan 15 '25 11:01 andiwand

Let's go 🚀

Jan 15 '25 12:01 paulgessinger

Quality Gate passed

Issues
9 New issues
0 Accepted issues

Measures
0 Security Hotspots
25.8% Coverage on New Code
2.7% Duplication on New Code

See analysis details on SonarQube Cloud

Jan 15 '25 14:01 sonarqubecloud[bot]

refactor!: Decouple navigation and stepping

📊: Physics performance monitoring for 1288d9ff725d1a71d345066eb3d1a5cd6e3356ef

physmon summary

Quality Gate passed

Walkthrough

Changes

Possibly related PRs

Suggested Labels

Suggested Reviewers

Poem

Finishing Touches

Chat

CodeRabbit Commands (Invoked using PR comments)

Other keywords and placeholders

CodeRabbit Configuration File (.coderabbit.yaml)

Documentation and Community

:white_check_mark: Athena integration test results [f060123b034411791d6c94a419acb2799f85297a]

:white_check_mark: All tests successful

Quality Gate passed

CodeRabbit Configuration File (`.coderabbit.yaml`)