| 1 | /*************************************************************************** |
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| 2 | * blitz/traversal.cc Space-filling curve based traversal orders |
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| 3 | * |
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| 4 | * $Id$ |
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| 5 | * |
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| 6 | * Copyright (C) 1997-2011 Todd Veldhuizen <tveldhui@acm.org> |
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| 7 | * |
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| 8 | * This file is a part of Blitz. |
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| 9 | * |
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| 10 | * Blitz is free software: you can redistribute it and/or modify |
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| 11 | * it under the terms of the GNU Lesser General Public License |
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| 12 | * as published by the Free Software Foundation, either version 3 |
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| 13 | * of the License, or (at your option) any later version. |
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| 14 | * |
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| 15 | * Blitz is distributed in the hope that it will be useful, |
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| 16 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 17 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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| 18 | * GNU Lesser General Public License for more details. |
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| 19 | * |
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| 20 | * You should have received a copy of the GNU Lesser General Public |
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| 21 | * License along with Blitz. If not, see <http://www.gnu.org/licenses/>. |
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| 22 | * |
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| 23 | * Suggestions: blitz-devel@lists.sourceforge.net |
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| 24 | * Bugs: blitz-support@lists.sourceforge.net |
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| 25 | * |
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| 26 | * For more information, please see the Blitz++ Home Page: |
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| 27 | * https://sourceforge.net/projects/blitz/ |
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| 28 | * |
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| 29 | ***************************************************************************/ |
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| 30 | |
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| 31 | #ifndef BZ_TRAVERSAL_CC |
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| 32 | #define BZ_TRAVERSAL_CC |
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| 33 | |
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| 34 | #ifndef BZ_TRAVERSAL_H |
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| 35 | #error <blitz/traversal.cc> must be included via <blitz/traversal.h> |
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| 36 | #endif |
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| 37 | |
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| 38 | BZ_NAMESPACE(blitz) |
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| 39 | |
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| 40 | // Next line is a workaround for Intel C++ V4.0 oddity, due |
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| 41 | // to Allan Stokes. |
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| 42 | static set<TraversalOrder<2> > *_bz_intel_kludge; |
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| 43 | |
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| 44 | //template<int N_dimensions> |
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| 45 | //_bz_typename TraversalOrderCollection<N_dimensions>::T_set |
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| 46 | // TraversalOrderCollection<N_dimensions>::traversals_; |
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| 47 | |
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| 48 | template<int N> |
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| 49 | void makeHilbert(Vector<TinyVector<int,N> >& coord, |
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| 50 | int x0, int y0, int xis, int xjs, |
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| 51 | int yis, int yjs, int n, int& i) |
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| 52 | { |
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| 53 | // N != 2 is not yet implemented. |
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| 54 | BZPRECONDITION(N == 2); |
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| 55 | |
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| 56 | if (!n) |
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| 57 | { |
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| 58 | if (i > coord.length(firstDim)) |
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| 59 | { |
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| 60 | cerr << "makeHilbert: vector not long enough" << endl; |
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| 61 | exit(1); |
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| 62 | } |
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| 63 | coord(i)[0] = x0 + (xis+yis)/2; |
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| 64 | coord(i)[1] = y0 + (xjs+yjs)/2; |
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| 65 | ++i; |
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| 66 | } |
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| 67 | else { |
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| 68 | makeHilbert(coord,x0,y0,yis/2, yjs/2, xis/2, xjs/2, n-1, i); |
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| 69 | makeHilbert(coord,x0+xis/2,y0+xjs/2,xis/2,xjs/2,yis/2,yjs/2,n-1,i); |
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| 70 | makeHilbert(coord,x0+xis/2+yis/2,y0+xjs/2+yjs/2,xis/2,xjs/2,yis/2, |
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| 71 | yjs/2,n-1,i); |
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| 72 | makeHilbert(coord,x0+xis/2+yis, y0+xjs/2+yjs, -yis/2,-yjs/2,-xis/2, |
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| 73 | -xjs/2,n-1,i); |
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| 74 | } |
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| 75 | } |
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| 76 | |
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| 77 | template<int N_dimensions> |
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| 78 | void MakeHilbertTraversal(Vector<TinyVector<int,N_dimensions> >& coord, |
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| 79 | int length) |
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| 80 | { |
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| 81 | // N_dimensions != 2 not yet implemented |
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| 82 | BZPRECONDITION(N_dimensions == 2); |
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| 83 | |
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| 84 | // The constant on the next line is ln(2) |
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| 85 | int d = (int)(::ceil(::log((double)length) / 0.693147180559945309417)); |
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| 86 | |
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| 87 | int N = 1 << d; |
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| 88 | const int Npoints = N*N; |
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| 89 | Vector<TinyVector<int,2> > coord2(Npoints); |
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| 90 | |
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| 91 | int i=0; |
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| 92 | makeHilbert(coord2,0,0,32768,0,0,32768,d,i); |
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| 93 | |
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| 94 | int xp0 = coord2(0)[0]; |
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| 95 | int yp0 = coord2(0)[1]; |
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| 96 | |
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| 97 | int j=0; |
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| 98 | |
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| 99 | coord.resize(length * length); |
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| 100 | |
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| 101 | for (int i=0; i < Npoints; ++i) |
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| 102 | { |
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| 103 | coord2(i)[0] = (coord2(i)[0]-xp0)/(2*xp0); |
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| 104 | coord2(i)[1] = (coord2(i)[1]-yp0)/(2*yp0); |
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| 105 | |
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| 106 | if ((coord2(i)[0] < length) && (coord2(i)[1] < length) |
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| 107 | && (coord2(i)[0] >= 0) && (coord2(i)[1] >= 0)) |
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| 108 | { |
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| 109 | coord(j)[0] = coord2(i)[0]; |
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| 110 | coord(j)[1] = coord2(i)[1]; |
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| 111 | ++j; |
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| 112 | } |
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| 113 | } |
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| 114 | } |
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| 115 | |
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| 116 | template<int N_dimensions> |
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| 117 | void generateFastTraversalOrder(const TinyVector<int,N_dimensions>& size) |
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| 118 | { |
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| 119 | BZPRECONDITION(N_dimensions == 2); |
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| 120 | BZPRECONDITION(size[0] == size[1]); |
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| 121 | |
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| 122 | TraversalOrderCollection<2> travCol; |
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| 123 | if (travCol.find(size)) |
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| 124 | return; |
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| 125 | |
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| 126 | Vector<TinyVector<int,2> > ordering(size[0]); |
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| 127 | |
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| 128 | MakeHilbertTraversal(ordering, size[0]); |
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| 129 | travCol.insert(TraversalOrder<2>(size, ordering)); |
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| 130 | } |
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| 131 | |
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| 132 | BZ_NAMESPACE_END |
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| 133 | |
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| 134 | #endif // BZ_TRAVERSAL_CC |
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