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source: branches/HeuristicLab.Problems.GrammaticalOptimization/HeuristicLab.Common/Extensions.cs @ 11799

Last change on this file since 11799 was 11799, checked in by gkronber, 9 years ago

#2283: performance tuning and reactivated random-roll-out policy in sequential search

File size: 1.9 KB
Line 
1using System;
2using System.Collections.Generic;
3using System.Linq;
4using System.Text;
5using System.Threading.Tasks;
6
7namespace HeuristicLab.Common {
8  public static class Extensions {
9    public static bool IsAlmost(this double x, double y) {
10      return Math.Abs(x - y) < 1.0e-12;
11    }
12
13    public static T SelectRandom<T>(this IEnumerable<T> xs, Random rand) {
14      var n = xs.Count();
15      return xs.ElementAt(rand.Next(n));
16    }
17
18    public static T SampleProportional<T>(this IEnumerable<T> elements, Random random, IEnumerable<double> weights) {
19      double total = weights.Sum();
20
21      var elemEnumerator = elements.GetEnumerator();
22      elemEnumerator.MoveNext();
23      var weightEnumerator = weights.GetEnumerator();
24      weightEnumerator.MoveNext();
25
26      var r = random.NextDouble() * total;
27      var agg = weightEnumerator.Current;
28
29      while (agg < r) {
30        weightEnumerator.MoveNext();
31        elemEnumerator.MoveNext();
32        agg += weightEnumerator.Current;
33      }
34      return elemEnumerator.Current;
35    }
36
37    public static double RSq(IEnumerable<double> xs, IEnumerable<double> ys) {
38      // two pass implementation, but we don't care
39      var meanX = xs.Average();
40      var meanY = ys.Average();
41
42      var s = 0.0;
43      var ssX = 0.0;
44      var ssY = 0.0;
45      var xEnum = xs.GetEnumerator();
46      var yEnum = ys.GetEnumerator();
47      while (xEnum.MoveNext() & yEnum.MoveNext()) {
48        var x = xEnum.Current;
49        var y = yEnum.Current;
50        s += (x - meanX) * (y - meanY);
51        ssX += (x - meanX) * (x - meanX);
52        ssY += (y - meanY) * (y - meanY);
53      }
54      if (xEnum.MoveNext() | yEnum.MoveNext()) throw new ArgumentException("lengths are not equal");
55
56      if (s.IsAlmost(0)) return 0;
57      if (ssX.IsAlmost(0) || ssY.IsAlmost(0)) return 0;
58      return s * s / (ssX * ssY);
59    }
60
61
62  }
63}
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