parallel-es/src/common/parallel/scheduling/default-parallel-scheduler.ts

Simple parallelization for EcmaScript

import {IDefaultInitializedParallelOptions} from "../parallel-options";
import {AbstractParallelScheduler, IParallelTaskScheduling} from "./abstract-parallel-scheduler";

/**
 * Default implementation of a parallel scheduler.
 * By default, creates 4 times as many tasks as the hardware concurrency allows ({@link IParallelOptions.maxConcurrencyLevel}).
 *
 * If the options define {@link IParallelOptions.maxValuesPerTask} or {@link IParallelOptions.minValuesPerTask}, then the
 * values are adjusted accordingly.
 */
export class DefaultParallelScheduler extends AbstractParallelScheduler {

    public getScheduling(totalNumberOfValues: number, options: IDefaultInitializedParallelOptions): IParallelTaskScheduling {
        let maxDegreeOfParallelism: number;

        if (options.maxDegreeOfParallelism) {
            maxDegreeOfParallelism = options.maxDegreeOfParallelism;
        } else {
            maxDegreeOfParallelism = options.threadPool.maxThreads * 4;
        }

        let valuesPerTask = totalNumberOfValues / maxDegreeOfParallelism;

        if (options.minValuesPerTask) {
            valuesPerTask = Math.min(Math.max(valuesPerTask, options.minValuesPerTask), totalNumberOfValues);
        }

        if (options.maxValuesPerTask) {
            valuesPerTask = Math.min(valuesPerTask, options.maxValuesPerTask);
        }

        valuesPerTask = Math.ceil(valuesPerTask);

        return {
            numberOfTasks: valuesPerTask === 0 ? 0 : Math.ceil(totalNumberOfValues / valuesPerTask),
            valuesPerTask
        };
    }
}