Microsoft Technology Licensing, LLC

Ritchie Zhao

Eric S Chung

Daniel Lo

Amar Phanishayee

Bita Darvish Rouhani

Yiren Zhao

Douglas Christopher Burger

Kalin Ovtcharov

Vahideh Akhlaghi

Nicolo Fusi

Jialiang Zhang

Ge Yang

Maximilian Golub

Apparatus and methods for training a neural network accelerator using quantized precision data formats are disclosed, and in particular for storing activation values from a neural network in a compressed format for use during forward and backward propagation training of the neural network. In certain examples of the disclosed technology, a computing system includes processors, memory, and a compressor in communication with the memory. The computing system is configured to perform forward propagation for a layer of a neural network to produced first activation values in a first block floating-point format. In some examples, activation values generated by forward propagation are converted by the compressor to a second block floating-point format having a narrower numerical precision than the first block floating-point format. The compressed activation values are stored in the memory, where they can be retrieved for use during back propagation.

Neural network activation compression with narrow block floating-point

Embodiments of the present disclosure include a system for optimizing an artificial neural network by configuring a model, based on a plurality of training parameters, to execute a training process, monitoring a plurality of statistics produced upon execution of the training process, and adjusting one or more of the training parameters, based on one or more of the statistics, to maintain at least one of the statistics within a predetermined range. In some embodiments, artificial intelligence (AI) processors may execute a training process on a model, the training process having an associated set of training parameters. Execution of the training process may produce a plurality of statistics. Control processor(s) coupled to the AI processor(s) may receive the statistics, and in accordance therewith, adjust one or more of the training parameters to maintain at least one of the statistics within a predetermined range during execution of the training process.

System for training an artificial neural network

Apparatus and methods for training a neural network accelerator using quantized precision data formats are disclosed, and, in particular, for adjusting floating-point formats used to store activation values during training. In certain examples of the disclosed technology, a computing system includes processors, memory, and a floating-point compressor in communication with the memory. The computing system is configured to produce a neural network comprising activation values expressed in a first floating-point format, select a second floating-point format for the neural network based on a performance metric, convert at least one of the activation values to the second floating-point format, and store the compressed activation values in the memory. Aspects of the second floating-point format that can be adjusted include the number of bits used to express mantissas, exponent format, use of non-uniform mantissas, and/or use of outlier values to express some of the mantissas.

Adjusting activation compression for neural network training

Apparatus and methods for training a neural network accelerator using quantized precision data formats having outlier values are disclosed, and in particular for storing activation values from a neural network in a compressed format for use during forward and backward propagation training of the neural network. In certain examples of the disclosed technology, a computing system is configured to perform forward propagation for a layer of a neural network to produced first activation values in a first block floating-point format. In some examples, activation values generated by forward propagation are converted by the compressor to a second block floating-point format having a narrower numerical precision than the first block floating-point format. Outlier values, comprising additional bits of mantissa and/or exponent are stored in ancillary storage for subset of the activation values. The compressed activation values are stored in the memory, where they can be retrieved for use during back propagation.

Neural network activation compression with outlier block floating-point

Quantization-aware neural architecture search ('QNAS') can be utilized to learn optimal hyperparameters for configuring an artificial neural network ('ANN') that quantizes activation values and/or weights. The hyperparameters can include model topology parameters, quantization parameters, and hardware architecture parameters. Model topology parameters specify the structure and connectivity of an ANN. Quantization parameters can define a quantization configuration for an ANN such as, for example, a bit width for a mantissa for storing activation values or weights generated by the layers of an ANN. The activation values and weights can be represented using a quantized-precision floating-point format, such as a block floating-point format (&#x201c;BFP&#x201d;) having a mantissa that has fewer bits than a mantissa in a normal-precision floating-point representation and a shared exponent.

Quantization-aware neural architecture search

Methods and apparatus are disclosed supporting a design flow for developing quantized neural networks. In one example of the disclosed technology, a method includes quantizing a normal-precision floating-point neural network model into a quantized format. For example, the quantized format can be a block floating-point format, where two or more elements of tensors in the neural network share a common exponent. A set of test input is applied to a normal-precision flooding point model and the corresponding quantized model and the respective output tensors are compared. Based on this comparison, hyperparameters or other attributes of the neural networks can be adjusted. Further, quantization parameters determining the widths of data and selection of shared exponents for the block floating-point format can be selected. An adjusted, quantized neural network is retrained and programmed into a hardware accelerator.

Flow for quantized neural networks

Machine learning is utilized to learn an optimized quantization configuration for an artificial neural network (ANN). For example, an ANN can be utilized to learn an optimal bit width for quantizing weights for layers of the ANN. The ANN can also be utilized to learn an optimal bit width for quantizing activation values for the layers of the ANN. Once the bit widths have been learned, they can be utilized at inference time to improve the performance of the ANN by quantizing the weights and activation values of the layers of the ANN.

Differential bit width neural architecture search

Methods and apparatus are disclosed for providing emulation of quantized precision operations in a neural network. In some examples, the quantized precision operations are performed in a block floating-point format where values of a tensor share a common exponent. Techniques for selecting higher precision or lower precision can be used based on a variety of input metrics. When converting to a quantized tensor, a residual tensor is produced. In one embodiment, an error value associated with converting from a normal-precision floating point number to the quantized tensor is used to determine whether to use the residual tensor in a dot product calculation. Using the residual tensor increases the precision of an output from a node. Selection of whether to use the residual tensor can depend on various input metrics including the error value, the layer number, the exponent value, the layer type, etc.

Residual quantization for neural networks

Machine learning may include training and drawing inference from artificial neural networks, processes which may include performing convolution and matrix multiplication operations. Convolution and matrix multiplication operations are performed using vectors of block floating-point (BFP) values that may include outliers. BFP format stores floating-point values using a plurality of mantissas of a fixed bit width and a shared exponent. Elements are outliers when they are too large to be represented precisely with the fixed bit width mantissa and shared exponent. Outlier values are split into two mantissas. One mantissa is stored in the vector with non-outliers, while the other mantissa is stored outside the vector. Operations, such as a dot product, may be performed on the vectors in part by combining the in-vector mantissa and exponent of an outlier value with the out-of-vector mantissa and exponent.

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Ithaca, NY, United States of America

Ritchie Zhao