[37] | 1 | //---------------------------------------------------------------------- |
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| 2 | // File: pr_queue_k.h |
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| 3 | // Programmer: Sunil Arya and David Mount |
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| 4 | // Description: Include file for priority queue with k items. |
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| 5 | // Last modified: 01/04/05 (Version 1.0) |
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| 6 | //---------------------------------------------------------------------- |
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| 7 | // Copyright (c) 1997-2005 University of Maryland and Sunil Arya and |
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| 8 | // David Mount. All Rights Reserved. |
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| 9 | // |
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| 10 | // This software and related documentation is part of the Approximate |
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| 11 | // Nearest Neighbor Library (ANN). This software is provided under |
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| 12 | // the provisions of the Lesser GNU Public License (LGPL). See the |
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| 13 | // file ../ReadMe.txt for further information. |
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| 14 | // |
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| 15 | // The University of Maryland (U.M.) and the authors make no |
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| 16 | // representations about the suitability or fitness of this software for |
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| 17 | // any purpose. It is provided "as is" without express or implied |
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| 18 | // warranty. |
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| 19 | //---------------------------------------------------------------------- |
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| 20 | // History: |
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| 21 | // Revision 0.1 03/04/98 |
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| 22 | // Initial release |
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| 23 | //---------------------------------------------------------------------- |
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| 24 | |
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| 25 | #ifndef PR_QUEUE_K_H |
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| 26 | #define PR_QUEUE_K_H |
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| 27 | |
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| 28 | #include <ANN/ANNx.h> // all ANN includes |
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| 29 | #include <ANN/ANNperf.h> // performance evaluation |
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| 30 | |
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| 31 | //---------------------------------------------------------------------- |
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| 32 | // Basic types |
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| 33 | //---------------------------------------------------------------------- |
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| 34 | typedef ANNdist PQKkey; // key field is distance |
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| 35 | typedef int PQKinfo; // info field is int |
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| 36 | |
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| 37 | //---------------------------------------------------------------------- |
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| 38 | // Constants |
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| 39 | // The NULL key value is used to initialize the priority queue, and |
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| 40 | // so it should be larger than any valid distance, so that it will |
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| 41 | // be replaced as legal distance values are inserted. The NULL |
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| 42 | // info value must be a nonvalid array index, we use ANN_NULL_IDX, |
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| 43 | // which is guaranteed to be negative. |
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| 44 | //---------------------------------------------------------------------- |
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| 45 | |
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| 46 | const PQKkey PQ_NULL_KEY = ANN_DIST_INF; // nonexistent key value |
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| 47 | const PQKinfo PQ_NULL_INFO = ANN_NULL_IDX; // nonexistent info value |
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| 48 | |
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| 49 | //---------------------------------------------------------------------- |
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| 50 | // ANNmin_k |
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| 51 | // An ANNmin_k structure is one which maintains the smallest |
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| 52 | // k values (of type PQKkey) and associated information (of type |
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| 53 | // PQKinfo). The special info and key values PQ_NULL_INFO and |
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| 54 | // PQ_NULL_KEY means that thise entry is empty. |
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| 55 | // |
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| 56 | // It is currently implemented using an array with k items. |
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| 57 | // Items are stored in increasing sorted order, and insertions |
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| 58 | // are made through standard insertion sort. (This is quite |
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| 59 | // inefficient, but current applications call for small values |
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| 60 | // of k and relatively few insertions.) |
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| 61 | // |
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| 62 | // Note that the list contains k+1 entries, but the last entry |
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| 63 | // is used as a simple placeholder and is otherwise ignored. |
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| 64 | //---------------------------------------------------------------------- |
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| 65 | |
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| 66 | class ANNmin_k { |
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| 67 | struct mk_node { // node in min_k structure |
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| 68 | PQKkey key; // key value |
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| 69 | PQKinfo info; // info field (user defined) |
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| 70 | }; |
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| 71 | |
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| 72 | int k; // max number of keys to store |
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| 73 | int n; // number of keys currently active |
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| 74 | mk_node *mk; // the list itself |
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| 75 | |
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| 76 | public: |
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| 77 | ANNmin_k(int max) // constructor (given max size) |
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| 78 | { |
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| 79 | n = 0; // initially no items |
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| 80 | k = max; // maximum number of items |
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| 81 | mk = new mk_node[max+1]; // sorted array of keys |
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| 82 | } |
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| 83 | |
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| 84 | ~ANNmin_k() // destructor |
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| 85 | { delete [] mk; } |
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| 86 | |
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| 87 | PQKkey ANNmin_key() // return minimum key |
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| 88 | { return (n > 0 ? mk[0].key : PQ_NULL_KEY); } |
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| 89 | |
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| 90 | PQKkey max_key() // return maximum key |
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| 91 | { return (n == k ? mk[k-1].key : PQ_NULL_KEY); } |
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| 92 | |
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| 93 | PQKkey ith_smallest_key(int i) // ith smallest key (i in [0..n-1]) |
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| 94 | { return (i < n ? mk[i].key : PQ_NULL_KEY); } |
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| 95 | |
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| 96 | PQKinfo ith_smallest_info(int i) // info for ith smallest (i in [0..n-1]) |
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| 97 | { return (i < n ? mk[i].info : PQ_NULL_INFO); } |
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| 98 | |
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| 99 | inline void insert( // insert item (inlined for speed) |
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| 100 | PQKkey kv, // key value |
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| 101 | PQKinfo inf) // item info |
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| 102 | { |
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| 103 | register int i; |
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| 104 | // slide larger values up |
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| 105 | for (i = n; i > 0; i--) { |
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| 106 | if (mk[i-1].key > kv) |
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| 107 | mk[i] = mk[i-1]; |
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| 108 | else |
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| 109 | break; |
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| 110 | } |
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| 111 | mk[i].key = kv; // store element here |
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| 112 | mk[i].info = inf; |
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| 113 | if (n < k) n++; // increment number of items |
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| 114 | ANN_FLOP(k-i+1) // increment floating ops |
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| 115 | } |
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| 116 | }; |
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| 117 | |
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| 118 | #endif |
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