A2Q: Accumulator-Aware Quantization with Guaranteed Overflow Avoidance
Ian Colbert Alessandro Pappalardo Jakoba Petri-Koenig
We present accumulator-aware quantization (A2Q), a novel weight quantization
method designed to train quantized neural networks (QNNs) to avoid overflow
when using low-precision accumulators during inference. A2Q introduces a unique
formulation inspired by weight normalization that constrains the L1-norm of
model weights according to accumulator bit width bounds that we derive. Thus,
in training QNNs for low-precision accumulation, A2Q also inherently promotes
unstructured weight sparsity to guarantee overflow avoidance. We apply our
method to deep learning-based computer vision tasks to show that A2Q can train
QNNs for low-precision accumulators while maintaining model accuracy
competitive with a floating-point baseline. In our evaluations, we consider the
impact of A2Q on both general-purpose platforms and programmable hardware.
However, we primarily target model deployment on FPGAs because they can be
programmed to fully exploit custom accumulator bit widths. Our experimentation
shows accumulator bit width significantly impacts the resource efficiency of
FPGA-based accelerators. On average across our benchmarks, A2Q offers up to a
2.3x reduction in resource utilization over 32-bit accumulator counterparts
with 99.2% of the floating-point model accuracy.