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      1 /*
      2  * [The "BSD licence"]
      3  * Copyright (c) 2005-2008 Terence Parr
      4  * All rights reserved.
      5  *
      6  * Conversion to C#:
      7  * Copyright (c) 2008-2009 Sam Harwell, Pixel Mine, Inc.
      8  * All rights reserved.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. The name of the author may not be used to endorse or promote products
     19  *    derived from this software without specific prior written permission.
     20  *
     21  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     22  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     23  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     24  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     26  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     27  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     28  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     29  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     30  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     31  */
     32 
     33 namespace Antlr.Runtime.Misc
     34 {
     35     using System.Collections.Generic;
     36 
     37     using Directory = System.IO.Directory;
     38     using Environment = System.Environment;
     39     using File = System.IO.File;
     40     using Math = System.Math;
     41     using Path = System.IO.Path;
     42 
     43     /** <summary>Stats routines needed by profiler etc...</summary>
     44      *
     45      *  <remarks>
     46      *  note that these routines return 0.0 if no values exist in the X[]
     47      *  which is not "correct", but it is useful so I don't generate NaN
     48      *  in my output
     49      *  </remarks>
     50      */
     51     public class Stats
     52     {
     53         public const string ANTLRWORKS_DIR = "antlrworks";
     54 
     55         /** <summary>Compute the sample (unbiased estimator) standard deviation following:</summary>
     56          *
     57          *  <remarks>
     58          *  Computing Deviations: Standard Accuracy
     59          *  Tony F. Chan and John Gregg Lewis
     60          *  Stanford University
     61          *  Communications of ACM September 1979 of Volume 22 the ACM Number 9
     62          *
     63          *  The "two-pass" method from the paper; supposed to have better
     64          *  numerical properties than the textbook summation/sqrt.  To me
     65          *  this looks like the textbook method, but I ain't no numerical
     66          *  methods guy.
     67          *  </remarks>
     68          */
     69         public static double Stddev( int[] X )
     70         {
     71             int m = X.Length;
     72             if ( m <= 1 )
     73             {
     74                 return 0;
     75             }
     76             double xbar = Average(X);
     77             double s2 = 0.0;
     78             for ( int i = 0; i < m; i++ )
     79             {
     80                 s2 += ( X[i] - xbar ) * ( X[i] - xbar );
     81             }
     82             s2 = s2 / ( m - 1 );
     83             return Math.Sqrt( s2 );
     84         }
     85         public static double Stddev( List<int> X )
     86         {
     87             int m = X.Count;
     88             if ( m <= 1 )
     89             {
     90                 return 0;
     91             }
     92             double xbar = Average(X);
     93             double s2 = 0.0;
     94             for ( int i = 0; i < m; i++ )
     95             {
     96                 s2 += ( X[i] - xbar ) * ( X[i] - xbar );
     97             }
     98             s2 = s2 / ( m - 1 );
     99             return Math.Sqrt( s2 );
    100         }
    101 
    102         /** <summary>Compute the sample mean</summary> */
    103         public static double Average(ICollection<int> X)
    104         {
    105             if (X.Count == 0)
    106                 return 0.0;
    107 
    108             double sum = 0.0;
    109             foreach (int i in X)
    110                 sum += i;
    111 
    112             return sum / X.Count;
    113         }
    114 
    115         public static void WriteReport( string filename, string data )
    116         {
    117             string absoluteFilename = GetAbsoluteFileName( filename );
    118 
    119             Directory.CreateDirectory( Path.GetDirectoryName( absoluteFilename ) );
    120             File.AppendAllText( absoluteFilename, data );
    121         }
    122 
    123         public static string GetAbsoluteFileName( string filename )
    124         {
    125             string personalFolder = Environment.GetFolderPath( Environment.SpecialFolder.Personal );
    126             return personalFolder + Path.DirectorySeparatorChar +
    127                         ANTLRWORKS_DIR + Path.DirectorySeparatorChar +
    128                         filename;
    129         }
    130     }
    131 }
    132