[6d6e829] | 1 | // |
---|
| 2 | // Cforall Version 1.0.0 Copyright (C) 2015 University of Waterloo |
---|
| 3 | // |
---|
| 4 | // The contents of this file are covered under the licence agreement in the |
---|
| 5 | // file "LICENCE" distributed with Cforall. |
---|
| 6 | // |
---|
| 7 | // FilterCombos.h -- |
---|
| 8 | // |
---|
| 9 | // Author : Aaron B. Moss |
---|
| 10 | // Created On : Mon Jul 23 16:05:00 2018 |
---|
| 11 | // Last Modified By : Aaron B. Moss |
---|
| 12 | // Last Modified On : Mon Jul 23 16:05:00 2018 |
---|
| 13 | // Update Count : 1 |
---|
| 14 | // |
---|
| 15 | |
---|
| 16 | #pragma once |
---|
| 17 | |
---|
| 18 | #include <vector> |
---|
| 19 | |
---|
| 20 | /// Type of index vector for combinations |
---|
| 21 | typedef std::vector<unsigned> Indices; |
---|
| 22 | |
---|
| 23 | /// Combo iterator that simply collects values into a vector, marking all values as valid. |
---|
| 24 | /// Prefer combos in typeops.h to use of IntoVectorComboIter with filterCombos |
---|
| 25 | /// @param T The element type of the vector. |
---|
| 26 | template<typename T> |
---|
| 27 | class IntoVectorComboIter { |
---|
| 28 | std::vector<T> crnt_combo; |
---|
| 29 | public: |
---|
| 30 | /// Outputs a vector of T |
---|
| 31 | using OutType = std::vector<T>; |
---|
| 32 | |
---|
| 33 | /// Adds the element to the current combination, always returning true for valid. |
---|
| 34 | bool append( const T& x ) { |
---|
| 35 | crnt_combo.push_back( x ); |
---|
| 36 | return true; |
---|
| 37 | } |
---|
| 38 | |
---|
| 39 | /// Removes the last element of the current combination. |
---|
| 40 | void backtrack() { crnt_combo.pop_back(); } |
---|
| 41 | |
---|
| 42 | /// Returns a copy of the current combination. |
---|
| 43 | OutType finalize() { return crnt_combo; } |
---|
| 44 | }; |
---|
| 45 | |
---|
| 46 | /// Filters combinations from qs by the given combo iterator. If the iterator rejects some prefix |
---|
| 47 | /// of a combination, it will not accept any combination with that prefix. |
---|
| 48 | /// qs should not be empty |
---|
| 49 | template<typename Q, typename ComboIter> |
---|
| 50 | auto filterCombos( const std::vector<Q>& qs, ComboIter&& iter ) |
---|
| 51 | -> std::vector<typename ComboIter::OutType> { |
---|
| 52 | unsigned n = qs.size(); // number of queues to combine |
---|
| 53 | |
---|
| 54 | std::vector<typename ComboIter::OutType> out; // filtered output |
---|
| 55 | for ( auto& q : qs ) if ( q.empty() ) return out; // return empty if any empty queue |
---|
| 56 | |
---|
| 57 | Indices inds; |
---|
| 58 | inds.reserve( n ); |
---|
| 59 | inds.push_back( 0 ); |
---|
| 60 | |
---|
| 61 | while (true) { |
---|
| 62 | unsigned i = inds.size() - 1; |
---|
| 63 | |
---|
| 64 | // iterate or keep successful match |
---|
| 65 | if ( iter.append( qs[i][inds.back()] ) ) { |
---|
| 66 | if ( i + 1 == n ) { |
---|
| 67 | // keep successful match of entire combination and continue iterating final place |
---|
| 68 | out.push_back( iter.finalize() ); |
---|
| 69 | iter.backtrack(); |
---|
| 70 | } else { |
---|
| 71 | // try to extend successful prefix |
---|
| 72 | inds.push_back( 0 ); |
---|
| 73 | continue; |
---|
| 74 | } |
---|
| 75 | } |
---|
| 76 | |
---|
| 77 | // move to next combo |
---|
| 78 | ++inds.back(); |
---|
| 79 | if ( inds.back() < qs[i].size() ) continue; |
---|
| 80 | |
---|
| 81 | // Otherwise done with the current row. |
---|
| 82 | // At this point, an invalid prefix is stored in inds and iter is in a state looking at |
---|
| 83 | // all but the final value in inds. Now backtrack to next prefix: |
---|
| 84 | inds.pop_back(); |
---|
| 85 | while ( ! inds.empty() ) { |
---|
| 86 | // try the next value at the previous index |
---|
| 87 | ++inds.back(); |
---|
| 88 | iter.backtrack(); |
---|
| 89 | if ( inds.back() < qs[inds.size()-1].size() ) break; |
---|
| 90 | // if the previous index is finished, backtrack out |
---|
| 91 | inds.pop_back(); |
---|
| 92 | } |
---|
| 93 | |
---|
| 94 | // Done if backtracked the entire array |
---|
| 95 | if ( inds.empty() ) return out; |
---|
| 96 | } |
---|
| 97 | } |
---|
| 98 | |
---|
| 99 | // Local Variables: // |
---|
| 100 | // tab-width: 4 // |
---|
| 101 | // mode: c++ // |
---|
| 102 | // compile-command: "make install" // |
---|
| 103 | // End: // |
---|