92 строки
3.1 KiB
C
92 строки
3.1 KiB
C
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//
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// Copyright (c) Microsoft. All rights reserved.
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// Licensed under the MIT license. See LICENSE.md file in the project root for full license information.
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//
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#pragma once
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#pragma warning(disable : 4127) // conditional expression is constant
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namespace Microsoft { namespace MSR { namespace CNTK {
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// RawType - input type to the quantizer
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// QuantizedType - output type of the quantizer
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template <class RawType, class QuantizedType>
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class IQuantizerBase
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{
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public:
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virtual void Quantize(const RawType* input, QuantizedType* output, size_t arraySize) = 0;
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virtual void Dequantize(const QuantizedType* input, RawType* output, size_t arraySize) = 0;
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protected:
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static int rangeMax;
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};
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template <class RawType, class QuantizedType>
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class SymmetricQuantizer : public IQuantizerBase<RawType, QuantizedType>
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{
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RawType m_quantizer;
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RawType m_invQuantizer;
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public:
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// elements - collection to be quantized
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// extraBits decreases the quantization normalizer to prevent integer overflow during BLAS routines.
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// Higher extraBits will decrease precision of quantization, but will make BLAS routines less prone to overflow.
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// For quantization with shorts, recommended value of extraBits is 1 or 2.
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SymmetricQuantizer(RawType* elements, size_t elementsSize, size_t extraBits)
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{
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if (elementsSize == 0)
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{
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LogicError("The sequence to be quantized is empty.");
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}
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RawType absMax = FindAbsMax(elements, elementsSize);
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SymmetricQuantizer(absMax, extraBits);
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}
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// absoluteMax - the range of the quantizer (normally represents maximum absolute value of the values in the collection to be quantized).
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// extraBits - see comment in another ctor
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SymmetricQuantizer(RawType absoluteMax, size_t extraBits)
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{
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RawType shiftedMax = absoluteMax * (1 << extraBits);
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if (shiftedMax == 0)
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{
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LogicError("The absolute max element in the sequence to be quantized is 0.");
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}
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m_quantizer = rangeMax / shiftedMax;
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m_invQuantizer = shiftedMax / rangeMax;
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}
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virtual void Quantize(const RawType* input, QuantizedType* output, size_t inputSize)
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{
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for (size_t i = 0; i < inputSize; i++)
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{
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output[i] = (QuantizedType) (input[i] * m_quantizer);
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}
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}
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virtual void Dequantize(const QuantizedType* input, RawType* output, size_t inputSize)
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{
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for (size_t i = 0; i < inputSize; i++)
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{
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output[i] = (RawType)(input[i] * m_invQuantizer);
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}
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}
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private:
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// Find absolute maximum value
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RawType FindAbsMax(RawType* elements, size_t elementsSize)
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{
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// in constructor we asserted that arraySize > 0
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RawType maxElem, minElem = elements[0];
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for (size_t i = 0; i < elementsSize; i++)
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{
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maxElem = std::max(maxElem, elements[i]);
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minElem = std::min(minElem, elements[i]);
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}
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return std::max(maxElem, std::abs(minElem));
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}
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};
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int IQuantizerBase<float, short>::rangeMax = SHRT_MAX;
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int IQuantizerBase<double, short>::rangeMax = SHRT_MAX;
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}}}
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