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/** | ||
* @license | ||
* Copyright 2024 Google LLC | ||
* SPDX-License-Identifier: Apache-2.0 | ||
*/ | ||
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import * as Lantern from '../types/lantern.js'; | ||
import {Metric} from '../metric.js'; | ||
import {BaseNode} from '../base-node.js'; | ||
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/** @typedef {import('../base-node.js').Node} Node */ | ||
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class MaxPotentialFID extends Metric { | ||
/** | ||
* @return {LH.Gatherer.Simulation.MetricCoefficients} | ||
*/ | ||
static get COEFFICIENTS() { | ||
return { | ||
intercept: 0, | ||
optimistic: 0.5, | ||
pessimistic: 0.5, | ||
}; | ||
} | ||
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/** | ||
* @param {Node} dependencyGraph | ||
* @return {Node} | ||
*/ | ||
static getOptimisticGraph(dependencyGraph) { | ||
return dependencyGraph; | ||
} | ||
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/** | ||
* @param {Node} dependencyGraph | ||
* @return {Node} | ||
*/ | ||
static getPessimisticGraph(dependencyGraph) { | ||
return dependencyGraph; | ||
} | ||
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/** | ||
* @param {LH.Gatherer.Simulation.Result} simulation | ||
* @param {import('../metric.js').Extras} extras | ||
* @return {LH.Gatherer.Simulation.Result} | ||
*/ | ||
static getEstimateFromSimulation(simulation, extras) { | ||
if (!extras.fcpResult) throw new Error('missing fcpResult'); | ||
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// Intentionally use the opposite FCP estimate, a more pessimistic FCP means that more tasks | ||
// are excluded from the FID computation, so a higher FCP means lower FID for same work. | ||
const fcpTimeInMs = extras.optimistic | ||
? extras.fcpResult.pessimisticEstimate.timeInMs | ||
: extras.fcpResult.optimisticEstimate.timeInMs; | ||
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const timings = MaxPotentialFID.getTimingsAfterFCP( | ||
simulation.nodeTimings, | ||
fcpTimeInMs | ||
); | ||
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return { | ||
timeInMs: Math.max(...timings.map(timing => timing.duration), 16), | ||
nodeTimings: simulation.nodeTimings, | ||
}; | ||
} | ||
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/** | ||
* @param {Lantern.Simulation.MetricComputationDataInput} data | ||
* @param {Omit<import('../metric.js').Extras, 'optimistic'>=} extras | ||
* @return {Promise<LH.Artifacts.LanternMetric>} | ||
*/ | ||
static compute(data, extras) { | ||
const fcpResult = extras?.fcpResult; | ||
if (!fcpResult) { | ||
throw new Error('FCP is required to calculate the Max Potential FID metric'); | ||
} | ||
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return super.compute(data, extras); | ||
} | ||
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/** | ||
* @param {LH.Gatherer.Simulation.Result['nodeTimings']} nodeTimings | ||
* @param {number} fcpTimeInMs | ||
* @return {Array<{duration: number}>} | ||
*/ | ||
static getTimingsAfterFCP(nodeTimings, fcpTimeInMs) { | ||
return Array.from(nodeTimings.entries()) | ||
.filter(([node, timing]) => node.type === BaseNode.TYPES.CPU && timing.endTime > fcpTimeInMs) | ||
.map(([_, timing]) => timing); | ||
} | ||
} | ||
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export {MaxPotentialFID}; |