Pipelines

Pipelines let you chain together data fitting, calculations, and validation steps into a single server-side workflow. A pipeline is defined as an ordered dictionary of named elements, each with an element_type and type-specific configuration.

Element types

Type	Purpose
entry	Provide initial parameter values to downstream elements
data_fit	Fit model parameters to experimental data
array_data_fit	Fit the same model separately at each value of an independent variable (e.g. temperature, SOC)
calculation	Run a calculation (e.g. OCP fitting)
validation	Validate a model against experimental data

Elements run in the order they appear. Later elements can reference results from earlier ones through the existing_parameters field.

Submitting a pipeline

Entry element

An entry element seeds the pipeline with known parameter values:

entry_config = {
    "element_type": "entry",
    "values": {
        "Negative particle diffusivity [m2.s-1]": 3.3e-14,
        "Positive particle diffusivity [m2.s-1]": 4e-15,
    },
}

Data-fit element

A data_fit element optimizes model parameters against uploaded measurement data. Reference measurement data stored in Ionworks with the db:<id> prefix:

measurement_id = "..."  # from client.cell_measurement.create()

datafit_config = {
    "element_type": "data_fit",
    "objectives": {
        "test_1C": {
            "objective": "CurrentDriven",
            "model": {"type": "SPMe"},
            "data": f"db:{measurement_id}",
            "parameters": {
                "Ambient temperature [K]": 298.15,
            },
        },
    },
    "parameters": {
        "Negative particle diffusivity [m2.s-1]": {
            "bounds": [1e-14, 1e-13],
            "initial_value": 2e-14,
        },
        "Positive particle diffusivity [m2.s-1]": {
            "bounds": [1e-15, 1e-14],
            "initial_value": 2e-15,
        },
    },
    "cost": {"type": "RMSE"},
    "optimizer": {"type": "ScipyDifferentialEvolution"},
}

Array-data-fit element

An array_data_fit element fits the same model separately at each key of the objectives dictionary, where the key is the value of some independent variable (e.g. temperature, midpoint stoichiometry, pulse SOC). It accepts the same top-level fields as data_fit; the only difference is the shape of objectives:

array_datafit_config = {
    "element_type": "array_data_fit",
    "objectives": {
        # key = value of the independent variable
        0.25: {"objective": "Pulse", "data": f"db:{m1_id}", ...},
        0.50: {"objective": "Pulse", "data": f"db:{m2_id}", ...},
        0.75: {"objective": "Pulse", "data": f"db:{m3_id}", ...},
    },
    "parameters": {
        "Positive particle diffusivity [m2.s-1]": {
            "bounds": [1e-15, 1e-13],
            "initial_value": 1e-14,
        },
    },
}

The result contains one fitted parameter value per independent-variable key, so the fitted parameter is returned as a 2×N array (independent-variable values along one row, fitted values along the other).

Combining elements

Pass all elements as a dictionary to client.pipeline.create():

pipeline = client.pipeline.create({
    "elements": {
        "entry": entry_config,
        "fit data": datafit_config,
    },
})
print(f"Pipeline ID: {pipeline.id}")

Polling for results

Pipelines run asynchronously. Poll client.pipeline.get() until the status is completed or failed:

import time

while True:
    pipeline = client.pipeline.get(pipeline.id)
    print(f"Status: {pipeline.status}")

    if pipeline.status == "completed":
        result = client.pipeline.result(pipeline.id)
        print("Fitted parameters:", result.element_results["fit data"])
        break
    elif pipeline.status == "failed":
        print("Pipeline failed:", pipeline.error)
        break

    time.sleep(2)

Listing pipelines

# All pipelines
pipelines = client.pipeline.list()

# Filter by project
pipelines = client.pipeline.list(project_id="...", limit=10)

Data sources

Pipeline elements can load data from several sources:

Prefix	Description
db:<measurement_id>	Measurement stored in Ionworks
file:<path>	Local CSV file
folder:<path>	Folder of CSV files

Next steps

To run forward simulations instead of fitting to data, see Simulations.