Google Research

Variable Precision Capabilities in RISC-V Processors

  • Andrea Bocco
  • Tiago T. Jost
  • Florent de Dinechin
  • Albert Cohen
  • Yves Durand
  • Christian Fabre


This work proposes to extend RISC-V with Variable Precision (VP) Floating-Point (FP) capabilities to accelerate scientific computing applications. It adopts the UNUM type I FP format in main memory to overcome the limitation of the IEEE 754 standard. Our work comprises: 1/ a VP FP RISC-V coprocessor; 2/ a RISC-V ISA extension for the unit, 3/ and a programming model to support VP floats in C/C++. Results have shown that our system can be more than 100x faster than the MPFR library when executing basic arithmetic operations.

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