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source: branches/2895_PushGP_GenealogyAnalysis/HeuristicLab.Problems.ProgramSynthesis/Push.Base/Extensions/EnumerableExtensions.cs @ 15771

Last change on this file since 15771 was 15771, checked in by bburlacu, 6 years ago

#2895: Add solution skeleton for PushGP with genealogy analysis.

File size: 928 bytes
Line 
1namespace HeuristicLab.Problems.ProgramSynthesis {
2  using System;
3  using System.Collections.Generic;
4  using System.Linq;
5
6  using HeuristicLab.Core;
7  using HeuristicLab.Random;
8
9  public static class EnumerableExtensions {
10    public static T RandomWeightedOrDefault<T>(this IEnumerable<T> items, IRandom random, Func<T, double> weightResolver) {
11      random = random ?? new MersenneTwister();
12      var totalWeight = items.Sum(weightResolver);
13
14      // The weight we are after...
15      var itemWeightIndex = random.NextDouble() * totalWeight;
16      var currentWeightIndex = 0d;
17
18      foreach (var item in items) {
19        currentWeightIndex += weightResolver(item);
20
21        // If we've hit or passed the weight we are after for this item then it's the one we want....
22        if (currentWeightIndex >= itemWeightIndex)
23          return item;
24      }
25
26      return default(T);
27    }
28  }
29}
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