/usr/include/casacore/lattices/Lattices/TiledLineStepper.h is in casacore-dev 2.2.0-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 | //# TiledLineStepper.h: Step a Vector cursor optimally through a tiled Lattice
//# Copyright (C) 1997,1998,1999,2000
//# Associated Universities, Inc. Washington DC, USA.
//#
//# This library is free software; you can redistribute it and/or modify it
//# under the terms of the GNU Library General Public License as published by
//# the Free Software Foundation; either version 2 of the License, or (at your
//# option) any later version.
//#
//# This library is distributed in the hope that it will be useful, but WITHOUT
//# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
//# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
//# License for more details.
//#
//# You should have received a copy of the GNU Library General Public License
//# along with this library; if not, write to the Free Software Foundation,
//# Inc., 675 Massachusetts Ave, Cambridge, MA 02139, USA.
//#
//# Correspondence concerning AIPS++ should be addressed as follows:
//# Internet email: aips2-request@nrao.edu.
//# Postal address: AIPS++ Project Office
//# National Radio Astronomy Observatory
//# 520 Edgemont Road
//# Charlottesville, VA 22903-2475 USA
//#
//# $Id$
#ifndef LATTICES_TILEDLINESTEPPER_H
#define LATTICES_TILEDLINESTEPPER_H
//# Includes
#include <casacore/casa/aips.h>
#include <casacore/lattices/Lattices/LatticeNavigator.h>
#include <casacore/lattices/Lattices/LatticeIndexer.h>
#include <casacore/casa/Arrays/IPosition.h>
namespace casacore { //# NAMESPACE CASACORE - BEGIN
// <summary>
// Step a Vector cursor optimally through a tiled Lattice.
// </summary>
// <use visibility=export>
// <reviewed reviewer="Peter Barnes" date="1999/10/30" tests="tTiledLineStepper.cc">
// </reviewed>
// <prerequisite>
// <li> <linkto class=LatticeNavigator> LatticeNavigator </linkto>
// </prerequisite>
// <etymology>
// TiledLineStepper is used to step a Vector cursor optimally through
// a Lattice that is tiled.
// </etymology>
// <synopsis>
// When you wish to traverse a Lattice (say, a PagedArray or an Image) you
// will usually create a LatticeIterator. Once created, you may attach a
// LatticeNavigator to the iterator. A TiledLineStepper, is a concrete class
// derived from the abstract LatticeNavigator that allows you to move
// a Vector cursor through the Lattice in a way that will minimize the
// amount of cache memory consumed.
// <p>
// Some Lattices (in particular PagedArrays) are stored (on disk) in
// tiles. For an N-dimensional Lattice a tile is an N-dimensional
// subsection with fewer elements along each axis. For example a Lattice of
// shape [512,512,4,32] may have a tile shape of [32,16,4,16], and there
// will be 16*32*1*2 (=1024) tiles in the entire Lattice. To allow efficient
// access of the data in a Lattice some tiles are cached in memory. As each
// tile may consume a fair bit of memory (in this example 128kBytes,
// assuming each element consumes 4 bytes), it is desirable to minimise the
// number of tiles held in the cache. But it is also desirable to minimise
// the number of times a tiles must be read into or written from the
// cache as this may require a time consuming operation like disk I/O.
// <p>
// Now suppose you wanted to traverse a Lattice with a Vector cursor of
// length 512 pixel aligned along the x-axis. Using a
// <linkto class=LatticeStepper>LatticeStepper</linkto>, each Vector is
// retrieved from the Lattice sequentially and without any consideration of
// the underlying tile shape. What is the optimal cache size for the above
// example?
// <p>
// Suppose we have a cache size of 16 ie., the number of tiles along the
// x-axis. Then Vectors beginning at positions [0,0,0,0] to [0,15,0,0] will
// be stored in the cache. But the next Vector beginning at position
// [0,16,0,0] will flush the cache and read in another 16 tiles. This I/O
// takes time and will occur 16 times for each plane in the four dimensional
// Lattice. Further when the cursor moves to position [0,0,1,0] the 16 tiles
// that where initially in the cache will need to be read again. To avoid
// all this cache I/O it is better to have a bigger cache.
// <p>
// Suppose the cache size is 16*32 (=512) ie., enough tiles to contain an
// (x,y)-plane. Then the cache size will not be flushed until the cursor is
// moved to position [0,0,0,16]. Further the cache will never need to read
// back into memory tiles that had previously been stored in there. The
// cache is big enough to store tiles until they have been completely
// used. But this cache is 64MBytes in size, and consumes too much memory
// for many computers.
// <p>
// This where a TiledLineStepper is useful. Because it knows the shape of the
// tiles in the underlying Lattice it moves the cursor to return all the
// Vectors in the smallest possible cache of tiles before moving on to the
// next set of tiles. Using the above example again, the TiledLineStepper will
// move the beginning of the Vector cursor in the following pattern.
// <srcblock>
// [0,0,0,0], [0,1,0,0], [0,2,0,0], ... [0,15,0,0]
// [0,0,1,0], [0,1,1,0], ... [0,15,1,0],
// ... [0,15,3,0],
// [0,0,0,1], ... [0,15,3,15]
// </srcblock>
// Moving the Vector cursor through all 16*4*16 (=1024 positions) can be
// done by caching only 16 tiles in memory (those along the x-axis). Hence
// the cache size need only be 2MBytes in size. Further once all 1024
// vectors have been returned it is not necessary to read these 16 tiles
// back into memory. All the data in those tiles has already been
// accessed. Using a TiledLineStepper rather than a LatticeStepper has,
// in this example, resulted in a drop in the required cache size from
// 64MBytes down to 2MBytes.
// <p>
// In constructing a TiledLineStepper, you specify the Lattice shape, the
// tile shape and the axis the Vector cursor will be aligned with. Specifying
// an axis=0 will align the cursor with the x-axis and axis=2 will produce a
// cursor that is along the z-axis. The length of the cursor is always the
// same as the number of elements in the Lattice along the axis the cursor
// is aligned with.
// <br>It is possible to use the function <src>subSection</src> to
// traverse only a subsection of the lattice.
// <p>
// The cursor position can be incremented or decremented to retrieve the next
// or previous Vector in the Lattice. The position of the next Vector in the
// Lattice will depend on the tile shape, and is described above. Within a tile
// the Vector cursor will move first through the x-axis and then the y-axis
// (assuming we have a cursor oriented along the z-axis). In general the lower
// dimensions will be exhausted (within a tile) before moving the cursor
// through higher dimensions. This intra-tile behaviour for cursor movement
// extends to the inter-tile movement of the cursor between tiles.
// </synopsis>
// <example>
// This example is of a global function that will do a 2-D inplace
// complex Fourier transform of an arbitrary large Lattice (which
// must have at least two dimensions).
//
// A two dimensional transform is done by successive one dimensional
// transforms along all the rows and then all the columns in the
// lattice. Scoping is used to destroy iterators once they have been
// used. This frees up the cache memory associated with the cursor in each
// iterator.
//
// <srcblock>
// void FFT2DComplex (Lattice<Complex>& cArray,
// const Bool direction)
// {
// const uInt ndim = cArray.ndim();
// AlwaysAssert(ndim > 1, AipsError);
// const IPosition latticeShape = cArray.shape();
// const uInt nx=latticeShape(0);
// const uInt ny=latticeShape(1);
// const IPosition tileShape = cArray.niceCursorShape();
//
// {
// TiledLineStepper tsx(latticeShape, tileShape, 0);
// LatticeIterator<Complex> lix(cArray, tsx);
// FFTServer<Float,Complex> fftx(IPosition(1, nx));
// for (lix.reset();!lix.atEnd();lix++) {
// fftx.fft(lix.rwVectorCursor(), direction);
// }
// }
// {
// TiledLineStepper tsy(latticeShape, tileShape, 1);
// LatticeIterator<Complex> liy(cArray, tsy);
// FFTServer<Float,Complex> ffty(IPosition(1, ny));
// for (liy.reset();!liy.atEnd();liy++) {
// ffty.fft(liy.rwVectorCursor(), direction);
// }
// }
// }
// </srcblock>
// </example>
// <motivation>
// Moving through a Lattice by equal sized chunks, and without regard
// to the nature of the data, is a basic and common procedure.
// </motivation>
// <todo asof="1997/03/28">
// <li> Support for Matrix and higher dimensional cursors can be used.
// </todo>
class TiledLineStepper : public LatticeNavigator
{
public:
// Construct a TiledLineStepper by specifying the Lattice shape,
// a tile shape and the axis along which the Vector cursor will lie
// (0 means the x-axis). Is is nearly always advisable to make the
// tileShape identical to the Lattice tileShape. This can be obtained by
// <src>lat.niceCursorShape(lat.advisedMaxPixels())</src>
// where <src>lat</src> is a Lattice object.
TiledLineStepper (const IPosition& latticeShape,
const IPosition& tileShape,
const uInt axis);
// The copy constructor uses copy semantics.
TiledLineStepper (const TiledLineStepper& other);
~TiledLineStepper();
// The assignment operator uses copy semantics.
TiledLineStepper& operator= (const TiledLineStepper& other);
// Increment operator (postfix or prefix version) - move the cursor
// forward one step. Returns True if the cursor was moved.
virtual Bool operator++(int);
// Decrement operator (postfix or prefix version) - move the cursor
// backwards one step. Returns True if the cursor was moved.
virtual Bool operator--(int);
// Function to move the cursor to the beginning of the Lattice. Also
// resets the number of steps (<src>nsteps</src> function) to zero.
virtual void reset();
// Function which returns "True" if the cursor is at the beginning of the
// Lattice, otherwise, returns "False"
virtual Bool atStart() const;
// Function which returns "True" if an attempt has been made to increment
// the cursor beyond the end of the Lattice.
virtual Bool atEnd() const;
// Function to return the number of steps (increments & decrements) taken
// since construction (or since last reset). This is a running count of
// all cursor movement (operator++ or operator--), even though
// N-increments followed by N-decrements will always leave the cursor in
// the original position.
virtual uInt nsteps() const;
// Function which returns the current position of the beginning of the
// cursor. The <src>position</src> function is relative to the origin
// in the main Lattice.
// <group>
virtual IPosition position() const;
// </group>
// Function which returns the current position of the end of the
// cursor. The <src>endPosition</src> function is relative to the origin
// in the main Lattice.
// <group>
virtual IPosition endPosition() const;
// </group>
// Functions which returns the shape of the Lattice being iterated
// through. <src>latticeShape</src> always returns the shape of the main
// Lattice while <src>subLatticeShape</src> returns the shape of any
// sub-Lattice defined using the <src>subSection</src> function.
// <group>
virtual IPosition latticeShape() const;
virtual IPosition subLatticeShape() const;
// </group>
// Function which returns the shape of the cursor. This always includes
// all axes (ie. it includes degenerates axes)
virtual IPosition cursorShape() const;
// Function which returns the axes of the cursor.
virtual IPosition cursorAxes() const;
// Function which returns the shape of the "tile" the cursor will iterate
// through before moving onto the next tile. THIS IS NOT THE SAME AS THE
// TILE SHAPE USED BY THE LATTICE. It is nearly the same except that the
// axis the cursor is aligned with is replaced by the shape of the Lattice
// on that axis. eg., If a Lattice has a shape of [512,512,4,32] and a
// tile shape of [32,16,4,16] then <src>tileShape()</src> will return
// [512,16,4,16] if the cursor is along the x-axis and [32,512,4,16] if the
// cursor is along the y-axis.
IPosition tileShape() const;
// Function which returns "True" if the increment/decrement operators have
// moved the cursor position such that part of the cursor beginning or end
// is hanging over the edge of the Lattice. This always returns False.
virtual Bool hangOver() const;
// Functions to specify a "section" of the Lattice to step over. A section
// is defined in terms of the Bottom Left Corner (blc), Top Right Corner
// (trc), and step size (inc), on ALL of its axes, including degenerate
// axes. The step size defaults to one if not specified.
// <group>
virtual void subSection (const IPosition& blc, const IPosition& trc);
virtual void subSection (const IPosition& blc, const IPosition& trc,
const IPosition& inc);
// </group>
// Return the bottom left hand corner (blc), top right corner (trc) or
// step size (increment) used by the current sub-Lattice. If no
// sub-Lattice has been defined (with the <src>subSection</src> function)
// these functions return blc=0, trc=latticeShape-1, increment=1, ie. the
// entire Lattice.
// <group>
virtual IPosition blc() const;
virtual IPosition trc() const;
virtual IPosition increment() const;
// </group>
// Return the axis path.
// See <linkto class=LatticeStepper>LatticeStepper</linkto> for a
// description and examples.
virtual const IPosition& axisPath() const;
// Function which returns a pointer to dynamic memory of an exact copy
// of this instance. The pointer returned by this function must
// be deleted externally.
virtual LatticeNavigator* clone() const;
// Function which checks the internal data of this class for correct
// dimensionality and consistant values.
// Returns True if everything is fine otherwise returns False
virtual Bool ok() const;
// Calculate the cache size (in tiles) for this type of access to a lattice
// in the given row of the tiled hypercube.
virtual uInt calcCacheSize (const IPosition& cubeShape,
const IPosition& tileShape,
uInt maxCacheSize, uInt bucketSize) const;
private:
// Prevent the default constructor from being used.
TiledLineStepper();
IPosition itsBlc; //# Bottom Left Corner
IPosition itsTrc; //# Top Right Corner
IPosition itsInc; //# Increment
LatticeIndexer itsSubSection; //# The current subsection
LatticeIndexer itsIndexer; //# For moving within a tile
LatticeIndexer itsTiler; //# For moving between tiles
IPosition itsIndexerCursorPos; //# The current position of the iterator.
IPosition itsTilerCursorPos; //# The current position of the iterator.
IPosition itsCursorShape; //# The shape of the cursor for itsIndexer
IPosition itsTileShape; //# The tile shape (= itsTiler cursor shape)
IPosition itsAxisPath; //# Path for traversing
uInt itsNsteps; //# The number of iterator steps taken so far;
uInt itsAxis; //# The axis containing the data vector
Bool itsEnd; //# Is the cursor beyond the end?
Bool itsStart; //# Is the cursor at the beginning?
};
} //# NAMESPACE CASACORE - END
#endif
|