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source: stable/HeuristicLab.ParallelEngine/3.3/ParallelEngine.cs

Last change on this file was 17181, checked in by swagner, 3 years ago

#2875: Merged r17180 from trunk to stable

File size: 5.4 KB
Line 
1#region License Information
2/* HeuristicLab
3 * Copyright (C) Heuristic and Evolutionary Algorithms Laboratory (HEAL)
4 *
5 * This file is part of HeuristicLab.
6 *
7 * HeuristicLab is free software: you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation, either version 3 of the License, or
10 * (at your option) any later version.
11 *
12 * HeuristicLab is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
19 */
20#endregion
21
22using System;
23using System.Collections.Generic;
24using System.Threading;
25using System.Threading.Tasks;
26using HeuristicLab.Common;
27using HeuristicLab.Core;
28using HEAL.Attic;
29
30namespace HeuristicLab.ParallelEngine {
31  /// <summary>
32  /// Represents an engine that executes its steps in parallel (if possible) using multiple threads.
33  /// This engine is suitable for parallel processing on shared memory systems which provide multiple cores.
34  /// </summary>
35  [StorableType("3B3366ED-22C5-4E4F-B307-E08FACCF0E20")]
36  [Item("Parallel Engine", "Engine for parallel execution of algorithms using multiple threads (suitable for shared memory systems with multiple cores).")]
37  public class ParallelEngine : Engine {
38    private CancellationToken cancellationToken;
39    private ParallelOptions parallelOptions;
40
41    [Storable(DefaultValue = -1)]
42    private int degreeOfParallelism;
43    public int DegreeOfParallelism {
44      get { return degreeOfParallelism; }
45      set {
46        if (degreeOfParallelism != value) {
47          degreeOfParallelism = value;
48          OnDegreeOfParallelismChanged();
49        }
50      }
51    }
52
53    [StorableConstructor]
54    protected ParallelEngine(StorableConstructorFlag _) : base(_) { }
55    protected ParallelEngine(ParallelEngine original, Cloner cloner)
56      : base(original, cloner) {
57      this.DegreeOfParallelism = original.DegreeOfParallelism;
58    }
59    public ParallelEngine()
60      : base() {
61      this.degreeOfParallelism = -1;
62    }
63
64    public override IDeepCloneable Clone(Cloner cloner) {
65      return new ParallelEngine(this, cloner);
66    }
67
68    public event EventHandler DegreeOfParallelismChanged;
69    protected void OnDegreeOfParallelismChanged() {
70      var handler = DegreeOfParallelismChanged;
71      if (handler != null) handler(this, EventArgs.Empty);
72    }
73
74
75    protected override void Run(CancellationToken cancellationToken) {
76      this.cancellationToken = cancellationToken;
77      parallelOptions = new ParallelOptions();
78      parallelOptions.MaxDegreeOfParallelism = DegreeOfParallelism;
79      parallelOptions.CancellationToken = cancellationToken;
80      Run(ExecutionStack);
81    }
82
83    private void Run(object state) {
84      Stack<IOperation> executionStack = (Stack<IOperation>)state;
85      IOperation next;
86      OperationCollection coll;
87      IAtomicOperation operation;
88
89      while (executionStack.Count > 0) {
90        cancellationToken.ThrowIfCancellationRequested();
91
92        next = executionStack.Pop();
93        if (next is OperationCollection) {
94          coll = (OperationCollection)next;
95          if (coll.Parallel) {
96            Stack<IOperation>[] stacks = new Stack<IOperation>[coll.Count];
97            for (int i = 0; i < coll.Count; i++) {
98              stacks[i] = new Stack<IOperation>();
99              stacks[i].Push(coll[i]);
100            }
101            try {
102              Parallel.ForEach(stacks, parallelOptions, Run);
103            } catch (OperationCanceledException) {
104              RepairStack(executionStack, stacks);
105              throw;
106            } catch (AggregateException) {
107              RepairStack(executionStack, stacks);
108              throw;
109            }
110          } else {
111            for (int i = coll.Count - 1; i >= 0; i--)
112              if (coll[i] != null) executionStack.Push(coll[i]);
113          }
114        } else if (next is IAtomicOperation) {
115          operation = (IAtomicOperation)next;
116          try {
117            next = operation.Operator.Execute((IExecutionContext)operation, cancellationToken);
118          }
119          catch (Exception ex) {
120            executionStack.Push(operation);
121            if (ex is OperationCanceledException) throw;
122            else throw new OperatorExecutionException(operation.Operator, ex);
123          }
124          if (next != null) executionStack.Push(next);
125        }
126      }
127    }
128
129    private static void RepairStack(Stack<IOperation> executionStack, Stack<IOperation>[] parallelExecutionStacks) {
130      OperationCollection remaining = new OperationCollection() { Parallel = true };
131      for (int i = 0; i < parallelExecutionStacks.Length; i++) {
132        if (parallelExecutionStacks[i].Count == 1)
133          remaining.Add(parallelExecutionStacks[i].Pop());
134        if (parallelExecutionStacks[i].Count > 1) {
135          OperationCollection ops = new OperationCollection();
136          while (parallelExecutionStacks[i].Count > 0)
137            ops.Add(parallelExecutionStacks[i].Pop());
138          remaining.Add(ops);
139        }
140      }
141      if (remaining.Count > 0) executionStack.Push(remaining);
142    }
143  }
144}
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