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ParallelExecutionSettings.cs
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ParallelExecutionSettings.cs
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// Copyright (c) Six Labors.
// Licensed under the Apache License, Version 2.0.
using System;
using System.Threading.Tasks;
using SixLabors.ImageSharp.Memory;
namespace SixLabors.ImageSharp.Advanced
{
/// <summary>
/// Defines execution settings for methods in <see cref="ParallelRowIterator"/>.
/// </summary>
public readonly struct ParallelExecutionSettings
{
/// <summary>
/// Default value for <see cref="MinimumPixelsProcessedPerTask"/>.
/// </summary>
public const int DefaultMinimumPixelsProcessedPerTask = 4096;
/// <summary>
/// Initializes a new instance of the <see cref="ParallelExecutionSettings"/> struct.
/// </summary>
/// <param name="maxDegreeOfParallelism">The value used for initializing <see cref="ParallelOptions.MaxDegreeOfParallelism"/> when using TPL.</param>
/// <param name="minimumPixelsProcessedPerTask">The value for <see cref="MinimumPixelsProcessedPerTask"/>.</param>
/// <param name="memoryAllocator">The <see cref="MemoryAllocator"/>.</param>
public ParallelExecutionSettings(
int maxDegreeOfParallelism,
int minimumPixelsProcessedPerTask,
MemoryAllocator memoryAllocator)
{
// Shall be compatible with ParallelOptions.MaxDegreeOfParallelism:
// https://docs.microsoft.com/en-us/dotnet/api/system.threading.tasks.paralleloptions.maxdegreeofparallelism
if (maxDegreeOfParallelism == 0 || maxDegreeOfParallelism < -1)
{
throw new ArgumentOutOfRangeException(nameof(maxDegreeOfParallelism));
}
Guard.MustBeGreaterThan(minimumPixelsProcessedPerTask, 0, nameof(minimumPixelsProcessedPerTask));
Guard.NotNull(memoryAllocator, nameof(memoryAllocator));
this.MaxDegreeOfParallelism = maxDegreeOfParallelism;
this.MinimumPixelsProcessedPerTask = minimumPixelsProcessedPerTask;
this.MemoryAllocator = memoryAllocator;
}
/// <summary>
/// Initializes a new instance of the <see cref="ParallelExecutionSettings"/> struct.
/// </summary>
/// <param name="maxDegreeOfParallelism">The value used for initializing <see cref="ParallelOptions.MaxDegreeOfParallelism"/> when using TPL.</param>
/// <param name="memoryAllocator">The <see cref="MemoryAllocator"/>.</param>
public ParallelExecutionSettings(int maxDegreeOfParallelism, MemoryAllocator memoryAllocator)
: this(maxDegreeOfParallelism, DefaultMinimumPixelsProcessedPerTask, memoryAllocator)
{
}
/// <summary>
/// Gets the <see cref="MemoryAllocator"/>.
/// </summary>
public MemoryAllocator MemoryAllocator { get; }
/// <summary>
/// Gets the value used for initializing <see cref="ParallelOptions.MaxDegreeOfParallelism"/> when using TPL.
/// </summary>
public int MaxDegreeOfParallelism { get; }
/// <summary>
/// Gets the minimum number of pixels being processed by a single task when parallelizing operations with TPL.
/// Launching tasks for pixel regions below this limit is not worth the overhead.
/// Initialized with <see cref="DefaultMinimumPixelsProcessedPerTask"/> by default,
/// the optimum value is operation specific. (The cheaper the operation, the larger the value is.)
/// </summary>
public int MinimumPixelsProcessedPerTask { get; }
/// <summary>
/// Creates a new instance of <see cref="ParallelExecutionSettings"/>
/// having <see cref="MinimumPixelsProcessedPerTask"/> multiplied by <paramref name="multiplier"/>
/// </summary>
/// <param name="multiplier">The value to multiply <see cref="MinimumPixelsProcessedPerTask"/> with.</param>
/// <returns>The modified <see cref="ParallelExecutionSettings"/>.</returns>
public ParallelExecutionSettings MultiplyMinimumPixelsPerTask(int multiplier)
{
Guard.MustBeGreaterThan(multiplier, 0, nameof(multiplier));
return new ParallelExecutionSettings(
this.MaxDegreeOfParallelism,
this.MinimumPixelsProcessedPerTask * multiplier,
this.MemoryAllocator);
}
/// <summary>
/// Get the default <see cref="SixLabors.ImageSharp.Advanced.ParallelExecutionSettings"/> for a <see cref="SixLabors.ImageSharp.Configuration"/>
/// </summary>
/// <param name="configuration">The <see cref="Configuration"/>.</param>
/// <returns>The <see cref="ParallelExecutionSettings"/>.</returns>
public static ParallelExecutionSettings FromConfiguration(Configuration configuration)
{
return new ParallelExecutionSettings(configuration.MaxDegreeOfParallelism, configuration.MemoryAllocator);
}
}
}