random.h

00001 /***********************************************************************
00002  * Software License Agreement (BSD License)
00003  *
00004  * Copyright 2008-2009  Marius Muja (mariusm@cs.ubc.ca). All rights reserved.
00005  * Copyright 2008-2009  David G. Lowe (lowe@cs.ubc.ca). All rights reserved.
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00010  * modification, are permitted provided that the following conditions
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00019  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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00030 
00031 #ifndef OPENCV_FLANN_RANDOM_H
00032 #define OPENCV_FLANN_RANDOM_H
00033 
00034 #include <algorithm>
00035 #include <cstdlib>
00036 #include <vector>
00037 
00038 #include "general.h"
00039 
00040 namespace cvflann
00041 {
00042 
00043 /**
00044  * Seeds the random number generator
00045  *  @param seed Random seed
00046  */
00047 inline void seed_random(unsigned int seed)
00048 {
00049     srand(seed);
00050 }
00051 
00052 /*
00053  * Generates a random double value.
00054  */
00055 /**
00056  * Generates a random double value.
00057  * @param high Upper limit
00058  * @param low Lower limit
00059  * @return Random double value
00060  */
00061 inline double rand_double(double high = 1.0, double low = 0)
00062 {
00063     return low + ((high-low) * (std::rand() / (RAND_MAX + 1.0)));
00064 }
00065 
00066 /**
00067  * Generates a random integer value.
00068  * @param high Upper limit
00069  * @param low Lower limit
00070  * @return Random integer value
00071  */
00072 inline int rand_int(int high = RAND_MAX, int low = 0)
00073 {
00074     return low + (int) ( double(high-low) * (std::rand() / (RAND_MAX + 1.0)));
00075 }
00076 
00077 /**
00078  * Random number generator that returns a distinct number from
00079  * the [0,n) interval each time.
00080  */
00081 class UniqueRandom
00082 {
00083     std::vector<int> vals_;
00084     int size_;
00085     int counter_;
00086 
00087 public:
00088     /**
00089      * Constructor.
00090      * @param n Size of the interval from which to generate
00091      * @return
00092      */
00093     UniqueRandom(int n)
00094     {
00095         init(n);
00096     }
00097 
00098     /**
00099      * Initializes the number generator.
00100      * @param n the size of the interval from which to generate random numbers.
00101      */
00102     void init(int n)
00103     {
00104         // create and initialize an array of size n
00105         vals_.resize(n);
00106         size_ = n;
00107         for (int i = 0; i < size_; ++i) vals_[i] = i;
00108 
00109         // shuffle the elements in the array
00110         std::random_shuffle(vals_.begin(), vals_.end());
00111 
00112         counter_ = 0;
00113     }
00114 
00115     /**
00116      * Return a distinct random integer in greater or equal to 0 and less
00117      * than 'n' on each call. It should be called maximum 'n' times.
00118      * Returns: a random integer
00119      */
00120     int next()
00121     {
00122         if (counter_ == size_) {
00123             return -1;
00124         }
00125         else {
00126             return vals_[counter_++];
00127         }
00128     }
00129 };
00130 
00131 }
00132 
00133 #endif //OPENCV_FLANN_RANDOM_H
00134