1 | namespace HeuristicLab.Problems.ProgramSynthesis.Push.Simplifier {
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2 | using System;
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3 | using HeuristicLab.Core;
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4 | using HeuristicLab.Problems.ProgramSynthesis.Push.Expressions;
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5 |
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6 | public class RandomSimplifier : ISimplifier {
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7 | public int Trys { get; set; }
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8 |
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9 | public PushProgram Simplify(PushProgram program, IRandom random, Predicate<PushProgram> isBetter) {
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10 |
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11 | if (program.TotalCount == 1) {
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12 | return isBetter(PushProgram.Empty) ? PushProgram.Empty : program;
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13 | }
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14 |
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15 | var copy = program.Copy();
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16 | var maxTries = Math.Min(Trys, program.TotalCount - 2);
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17 | var successfulRemoves = 0;
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18 |
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19 | for (var i = 0; i < maxTries; i++) {
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20 | var rndIndex = random.Next(1, program.TotalCount - 1 - successfulRemoves);
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21 | var node = copy.GetFromTree(
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22 | rndIndex,
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23 | (super, parent, child, childIndex, parentIndex) => new {
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24 | Super = super,
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25 | Parent = parent,
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26 | ChildIndex = childIndex,
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27 | ParentIndex = parentIndex
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28 | });
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29 |
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30 | var oldParentExpressions = node.Parent.State;
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31 | var newParentExpressions = RemoveAt(oldParentExpressions, node.ChildIndex);
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32 | var newParent = new PushProgram(newParentExpressions);
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33 |
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34 | var superExpressions = node.Super == null ? copy.State : node.Super.State;
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35 | superExpressions[node.ParentIndex] = newParent;
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36 |
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37 | if (isBetter(copy)) {
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38 | successfulRemoves++;
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39 | } else {
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40 | superExpressions[node.ParentIndex] = node.Parent;
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41 | }
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42 | }
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43 |
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44 | return copy;
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45 | }
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46 |
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47 | private static T[] RemoveAt<T>(T[] source, int index) {
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48 | var dest = new T[source.Length - 1];
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49 | if (index > 0)
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50 | Array.Copy(source, 0, dest, 0, index);
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51 |
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52 | if (index < source.Length - 1)
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53 | Array.Copy(source, index + 1, dest, index, source.Length - index - 1);
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54 |
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55 | return dest;
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56 | }
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57 | }
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58 | } |
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