Precision–Energy–Throughput Scaling of Generic Matrix Multiplication and Convolution Kernels via Linear Projections

Generic matrix multiplication (GEMM) and convolution (CONV)/cross-correlation kernels often constitute the bulk of the compute- and memory-intensive processing within image/audio recognition and matching systems. We propose a novel method to scale the energy and processing throughput of GEMM and CONV kernels for such error-tolerant multimedia applications by adjusting the precision of computation. Our technique employs linear projections to the input matrix or signal data during the top-level GEMM and CONV blocking and reordering. The GEMM and CONV kernel processing then uses the projected inputs and the results are accumulated to form the final outputs. Throughput and energy scaling takes place by changing the number of projections computed by each kernel, which in turn produces approximate results, i.e., changes the precision of the performed computation. Results derived from a voltage- and frequency-scaled ARM Cortex A15 processor running face recognition and music-matching algorithms demonstrate that the proposed approach allows for a 280%-440% increase of processing throughput and a 75%-80% decrease of energy consumption against the optimized GEMM and CONV kernels without any impact on the obtained recognition or matching accuracy. Even higher gains can be obtained, if one is willing to tolerate some reduction in the accuracy of the recognition and matching applications.