96 lines
3.1 KiB
C++
96 lines
3.1 KiB
C++
//============================================================================
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// Copyright (c) Kitware, Inc.
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// All rights reserved.
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// See LICENSE.txt for details.
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//
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// This software is distributed WITHOUT ANY WARRANTY; without even
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// the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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// PURPOSE. See the above copyright notice for more information.
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//============================================================================
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#ifndef vtk_m_worklet_FieldEntropy_h
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#define vtk_m_worklet_FieldEntropy_h
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#include <vtkm/Math.h>
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#include <vtkm/cont/Algorithm.h>
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#include <vtkm/cont/ArrayHandle.h>
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#include <vtkm/cont/ArrayHandleCounting.h>
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#include <vtkm/worklet/DispatcherMapField.h>
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#include <vtkm/worklet/FieldHistogram.h>
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#include <vtkm/worklet/WorkletMapField.h>
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#include <vtkm/cont/Field.h>
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namespace vtkm
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{
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namespace worklet
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{
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//simple functor that returns basic statistics
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class FieldEntropy
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{
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public:
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// For each bin, calculate its information content (log2)
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class SetBinInformationContent : public vtkm::worklet::WorkletMapField
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{
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public:
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using ControlSignature = void(FieldIn freq, FieldOut informationContent);
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using ExecutionSignature = void(_1, _2);
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vtkm::Float64 FreqSum;
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VTKM_CONT
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SetBinInformationContent(vtkm::Float64 _freqSum)
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: FreqSum(_freqSum)
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{
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}
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template <typename FreqType>
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VTKM_EXEC void operator()(const FreqType& freq, vtkm::Float64& informationContent) const
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{
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vtkm::Float64 p = ((vtkm::Float64)freq) / FreqSum;
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if (p > 0)
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informationContent = -1 * p * vtkm::Log2(p);
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else
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informationContent = 0;
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}
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};
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// Execute the entropy computation filter given data(a field) and number of bins
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// Returns:
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// Entropy (log2) of the field of the data
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template <typename FieldType, typename Storage>
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vtkm::Float64 Run(vtkm::cont::ArrayHandle<FieldType, Storage> fieldArray, vtkm::Id numberOfBins)
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{
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///// calculate histogram using FieldHistogram worklet /////
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vtkm::Range range;
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FieldType delta;
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vtkm::cont::ArrayHandle<vtkm::Id> binArray;
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vtkm::worklet::FieldHistogram histogram;
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histogram.Run(fieldArray, numberOfBins, range, delta, binArray);
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///// calculate sum of frequency of the histogram /////
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vtkm::Id initFreqSumValue = 0;
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vtkm::Id freqSum = vtkm::cont::Algorithm::Reduce(binArray, initFreqSumValue, vtkm::Sum());
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///// calculate information content of each bin using self-define worklet /////
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vtkm::cont::ArrayHandle<vtkm::Float64> informationContent;
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SetBinInformationContent binWorklet(static_cast<vtkm::Float64>(freqSum));
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vtkm::worklet::DispatcherMapField<SetBinInformationContent> setBinInformationContentDispatcher(
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binWorklet);
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setBinInformationContentDispatcher.Invoke(binArray, informationContent);
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///// calculate entropy by summing up information conetent of all bins /////
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vtkm::Float64 initEntropyValue = 0;
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vtkm::Float64 entropy =
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vtkm::cont::Algorithm::Reduce(informationContent, initEntropyValue, vtkm::Sum());
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return entropy;
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}
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};
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}
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} // namespace vtkm::worklet
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#endif // vtk_m_worklet_FieldEntropy_h
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