Added InputParameter support in PyBamm experiments by Rishab87 · Pull Request #4826 · pybamm-team/PyBaMM

Rishab87 · 2025-02-07T17:46:56Z

Description

Added InputParameter support in experiments, now you can pass them something like this:

current_step = pybamm.step.current(1, input_parameters=pybamm.InputParameter("I_app"), termination="2.5 V")
experiment = pybamm.Experiment(
    input_parameters={"I_app": 1},
    termination="2.5 V",
    operating_conditions=[current_step],
)

Fixes #4799

Type of change

Please add a line in the relevant section of CHANGELOG.md to document the change (include PR #) - note reverse order of PR #s. If necessary, also add to the list of breaking changes.

New feature (non-breaking change which adds functionality)
Optimization (back-end change that speeds up the code)
Bug fix (non-breaking change which fixes an issue)

Key checklist:

No style issues: $ pre-commit run (or $ nox -s pre-commit) (see CONTRIBUTING.md for how to set this up to run automatically when committing locally, in just two lines of code)
All tests pass: $ python -m pytest (or $ nox -s tests)
The documentation builds: $ python -m pytest --doctest-plus src (or $ nox -s doctests)

You can run integration tests, unit tests, and doctests together at once, using $ nox -s quick.

Further checks:

Code is commented, particularly in hard-to-understand areas
Tests added that prove fix is effective or that feature works

valentinsulzer

Thanks for taking this on but this isn't quite what I had in mind, the interface should be:

step = pybamm.step.current(pybamm.InputParameter("I_app"), termination="2.5 V")
experiment = pybamm.Experiment([step])
sim = pybamm.Simulation(..., experiment=experiment)
sim.solve(inputs={"I_app": 1})

…o input-params

…input-params

Rishab87 · 2025-02-15T09:14:40Z

made changes, now user can pass input params like this:

step = pybamm.step.current(pybamm.InputParameter("I_app"), termination="2.5 V")
experiment = pybamm.Experiment([step])
sim = pybamm.Simulation(..., experiment=experiment)
sim.solve(inputs={"I_app": 1})

codecov · 2025-02-15T16:11:29Z

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.70%. Comparing base (0d5af5c) to head (f21f01a).
Report is 83 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #4826   +/-   ##
========================================
  Coverage    98.70%   98.70%           
========================================
  Files          304      304           
  Lines        23432    23452   +20     
========================================
+ Hits         23129    23149   +20     
  Misses         303      303

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…input-params

Rishab87 · 2025-02-16T06:32:09Z

Just a follow up anything else I need to change?

MarcBerliner

@Rishab87 thanks for putting this PR together! I left a few comments

aabills · 2025-02-18T16:42:22Z

The operator is only a property of the termination function. For example, if the termination function is "2.5 V", whether that means that the step terminates when the battery goes above 2.5 V or below 2.5 V is not well defined. The workaround for this in the past was that we could detect whether the battery was charging or discharging based on the current, and to assume that the termination would be hit if the battery goes above the voltage during charge or below during discharge. This is actually the only reason we ever needed to know the direction anyway. In the case that it is an input parameter, we can no longer calculate whether the battery is charging or discharging a priori, so instead, we have to provide an operator to fully define the event.

So for this PR, we need to ensure that any termination has an operator, because we cannot make the assumption. We probably want to keep the string parsing available, so a nice syntax would be "{operator} {value} {unit}", e.g. "< 2.5 V". But the operator must be in the termination, not the step.

Rishab87 · 2025-02-19T17:17:07Z

@aabills I've made changes accordingly just as you told now operator gets passed in termination like "< 2.5 V". And thanks for explaining about why we need directions in first place and why we need an operator now it helped me a lot while making changes

Rishab87 · 2025-02-20T05:42:32Z

@aabills thanks for the review I've added the callable case and also added few test cases accordingly to ensure full coverage

aabills

So close! Just one more change and this is good from my side

Rishab87 · 2025-02-20T17:32:29Z

@aabills I've changed the code and added a check to see if symbol has input params

aabills · 2025-02-20T22:35:39Z

Looks good! Fix coverage and you're good to go from my side. @MarcBerliner @valentinsulzer anything else from y'all?

aabills · 2025-02-20T22:38:52Z

Oh and don't forget to add something to the CHANGELOG.md

aabills · 2025-02-20T22:40:54Z

Also fix this failing integration test.

valentinsulzer

looks good to me

Rishab87 · 2025-02-21T08:52:06Z

@aabills added my PR to changelog and tests for full coverage. Also fixed the integration test

aabills

Looks great to me!

MarcBerliner

Thanks @Rishab87! Looks great

…om termination check When pybamm.step.current/voltage/power/resistance is called with a Python callable value(t) that genuinely depends on t, BaseStep.__init__ rewrites self.value as value(pybamm.t - pybamm.InputParameter('start time')) so that the runtime start time injected by Simulation can offset time at solve. That InputParameter is an implementation detail — its name is reserved by Simulation._START_TIME_INPUT — but _check_input_params was walking the symbol tree and reporting True for *any* InputParameter leaf, including this internal one. That breaks two downstream assumptions: 1. _parse_termination then raises ValueError: Termination must include an operator when using InputParameter. against plain string terminations like '4.3 V' even though the user never passed an InputParameter. This is the regression reported in pybamm-team#5018, where code that worked in 25.1 stops working in 25.4+ (the operator-or-bust check was added by pybamm-team#4826). 2. value_based_charge_or_discharge returns None for every callable-driven step, so direction inference silently goes away. The fix narrows _check_input_params to user-supplied InputParameters by filtering out leaves whose name is 'start time'. Genuine user inputs (e.g. pybamm.InputParameter('I_app') or I_coeff * pybamm.t) still trigger the check, so the operator requirement introduced by pybamm-team#4826 is preserved. Tests cover the helper directly, both branches of the filter (internal-only vs mixed with a user input), the operator-free string termination path, the [CustomTermination, '4.3 V'] shape from the OP's reproducer, the restored direction inference, and a non-regression on the existing 'must include an operator' guard for true InputParameter values.

added input params in exp and steps

a18ee59

Rishab87 requested review from TomTranter, brosaplanella, martinjrobins, rtimms and valentinsulzer as code owners February 7, 2025 17:46

Rishab87 and others added 2 commits February 8, 2025 10:20

fixed failing tests

07acef8

Merge branch 'develop' into input-params

eb680ef

valentinsulzer requested changes Feb 12, 2025

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Rishab87 added 3 commits February 15, 2025 14:32

changed user interface for input params

0625df8

Merge branch 'input-params' of https://github.com/Rishab87/PyBaMM int…

a77bcf5

…o input-params

Merge branch 'develop' of https://github.com/pybamm-team/PyBaMM into …

65c1608

…input-params

Rishab87 added 3 commits February 15, 2025 22:24

minor changes

4960fed

Merge branch 'develop' of https://github.com/pybamm-team/PyBaMM into …

6b487fd

…input-params

pulling develop and minor change

43610bb

Rishab87 requested a review from a team as a code owner February 16, 2025 06:30

Rishab87 requested a review from valentinsulzer February 16, 2025 09:28

MarcBerliner requested changes Feb 17, 2025

View reviewed changes

Comment thread src/pybamm/experiment/step/base_step.py Outdated

Comment thread src/pybamm/experiment/step/base_step.py Outdated

Comment thread src/pybamm/experiment/step/base_step.py Outdated

Comment thread src/pybamm/experiment/step/base_step.py Outdated

force user to pass operator

cd2820a

Rishab87 requested a review from MarcBerliner February 18, 2025 14:41

Merge branch 'develop' into input-params

dd464e1

aabills requested changes Feb 18, 2025

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Comment thread src/pybamm/experiment/step/base_step.py Outdated

added operator in termination

93736d1

Rishab87 requested a review from aabills February 19, 2025 17:18

minor changes

a5c3fd3

minor changes

7d7aa27

Rishab87 requested a review from aabills February 20, 2025 05:42

added necessary condition

f5c8986

aabills requested changes Feb 20, 2025

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Comment thread src/pybamm/experiment/step/base_step.py Outdated

added check for input params in symbol

435ad80

Rishab87 requested a review from aabills February 20, 2025 17:32

valentinsulzer previously approved these changes Feb 20, 2025

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aabills previously approved these changes Feb 21, 2025

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aabills self-requested a review February 21, 2025 00:53

added PR to changelog and tests for coverage

9084495

Rishab87 dismissed stale reviews from aabills and valentinsulzer via 9084495 February 21, 2025 08:50

aabills approved these changes Feb 21, 2025

View reviewed changes

MarcBerliner added 2 commits February 21, 2025 10:34

Merge branch 'develop' into input-params

e502dc7

Merge branch 'develop' into input-params

f21f01a

MarcBerliner approved these changes Feb 21, 2025

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MarcBerliner enabled auto-merge (squash) February 21, 2025 17:00

MarcBerliner merged commit 651584f into pybamm-team:develop Feb 21, 2025

gaoflow mentioned this pull request May 28, 2026

Fix #5018: exclude internal 'start time' InputParameter from termination check #5545

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Rishab87 commented Feb 7, 2025

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