Mercurial > hg > svcore
view data/model/PowerOfSqrtTwoZoomConstraint.cpp @ 335:02d2ad95ea52 spectrogram-cache-rejig
* Get storage advice for each cache in an FFT data server. Allows us to be
more confident about the actual memory situation and cut over from memory
to disc part way through an FFT calculation if necessary. StorageAdviser
is now a bit too optimistic though (it's too keen to allocate large numbers
of small blocks in memory).
author | Chris Cannam |
---|---|
date | Tue, 13 Nov 2007 13:54:10 +0000 |
parents | 3a13b0d4934e |
children | 166c22eff678 |
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/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*- vi:set ts=8 sts=4 sw=4: */ /* Sonic Visualiser An audio file viewer and annotation editor. Centre for Digital Music, Queen Mary, University of London. This file copyright 2006 Chris Cannam. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. See the file COPYING included with this distribution for more information. */ #include "PowerOfSqrtTwoZoomConstraint.h" #include <iostream> #include <cmath> size_t PowerOfSqrtTwoZoomConstraint::getNearestBlockSize(size_t blockSize, RoundingDirection dir) const { int type, power; size_t rv = getNearestBlockSize(blockSize, type, power, dir); return rv; } size_t PowerOfSqrtTwoZoomConstraint::getNearestBlockSize(size_t blockSize, int &type, int &power, RoundingDirection dir) const { // std::cerr << "given " << blockSize << std::endl; size_t minCachePower = getMinCachePower(); if (blockSize < (1U << minCachePower)) { type = -1; power = 0; float val = 1.0, prevVal = 1.0; while (val + 0.01 < blockSize) { prevVal = val; val *= sqrt(2); } size_t rval; if (dir == RoundUp) rval = size_t(val + 0.01); else if (dir == RoundDown) rval = size_t(prevVal + 0.01); else if (val - blockSize < blockSize - prevVal) rval = size_t(val + 0.01); else rval = size_t(prevVal + 0.01); // std::cerr << "returning " << rval << std::endl; return rval; } unsigned int prevBase = (1 << minCachePower); unsigned int prevPower = minCachePower; unsigned int prevType = 0; size_t result = 0; for (unsigned int i = 0; ; ++i) { power = minCachePower + i/2; type = i % 2; unsigned int base; if (type == 0) { base = (1 << power); } else { base = (((unsigned int)((1 << minCachePower) * sqrt(2) + 0.01)) << (power - minCachePower)); } // std::cerr << "Testing base " << base << std::endl; if (base >= blockSize) { if (dir == RoundNearest) { if (base - blockSize < blockSize - prevBase) { dir = RoundUp; } else { dir = RoundDown; } } if (dir == RoundUp) { result = base; break; } else { type = prevType; power = prevPower; result = prevBase; break; } } prevType = type; prevPower = power; prevBase = base; } if (result > getMaxZoomLevel()) result = getMaxZoomLevel(); return result; }