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106 lines
2.9 KiB
106 lines
2.9 KiB
//==============================================================================
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//
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// Copyright (c) 2016-
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// Authors:
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// * Dave Parker <d.a.parker@cs.bham.ac.uk> (University of Birmingham)
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// * Joachim Klein <klein@tcs.inf.tu-dresden.de> (TU Dresden)
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//
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//------------------------------------------------------------------------------
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//
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// This file is part of PRISM.
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//
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// PRISM is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 2 of the License, or
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// (at your option) any later version.
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//
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// PRISM is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with PRISM; if not, write to the Free Software Foundation,
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// Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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//
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//==============================================================================
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#ifndef MEASURE_H
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#define MEASURE_H
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#include <cstddef> // for std::size_t type
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#include <math.h> // for isinf
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#include <limits>
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/**
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* Measure: Computes maximum element-wise difference between value vectors.
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* In relative mode, the difference is scaled by the value.
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*/
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class MeasureSupNorm {
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private:
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// relative mode?
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const bool relative;
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// the current maximal value
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double sup_norm;
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public:
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/** Constructor, set relative flag */
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MeasureSupNorm(bool relative) : relative(relative) {
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reset();
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}
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/** Reset for new measurement */
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void reset() {
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sup_norm = 0.0;
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}
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/** Relative mode? */
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bool isRelative() const {
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return relative;
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}
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/**
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* Do the measurement for a single pair of values.
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* For relative mode, the second value is used as the divisor.
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*/
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inline void measure(double v1, double v2) {
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double x;
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// compute absolute of difference
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x = fabs(v2 - v1);
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if (relative) {
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// for relative mode: divide by second value
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// We take the absolute value of v2 to ensure that
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// x remains non-negative. v2 can become negative e.g.
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// during iterations with over-relaxation with large
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// omega values.
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// Note: if v2 is 0, then x will become +inf for x>0 and NaN for x=0, i.e., v1=v2=0
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// In the later case, the max computation below will ignore the NaN,
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// as NaN > y is false for all y
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x /= fabs(v2);
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}
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// sup_norm = max { x, sup_norm }
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if (x > sup_norm) {
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sup_norm = x;
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}
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}
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/**
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* Do the measurement for two value arrays of size n.
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* For relative mode, the values of the second array are used as the divisors.
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*/
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inline void measure(const double *soln, const double *soln2, std::size_t n) {
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for (std::size_t i = 0; i < n; i++) {
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measure(soln[i], soln2[i]);
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}
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}
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/** Return the measured value */
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double value() const {
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return sup_norm;
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}
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};
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#endif
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