Performance evaluation of branch-free fused multiply-add algorithms for multi-component-type multiple-precision floating-point arithmetic

Abstract

High performance in multi-component multiple-precision arithmetic constructed from existing floating-point operations using error-free transformations (EFTs), can be achieved by employing branch-free algorithms that eliminate if-branches. Zhang and Aiken proposed branch-free algorithms for addition and multiplication in double-word(DW), triple-word(TW), and quadruple-word(QW) arithmetic. Among these, we implemented the TW and QW variants, for which substantial performance improvements over existing algorithms can be expected, and demonstrated that they indeed contribute to acceleration. In this paper, we propose new branch-free fused multiply-add operations for DW, TW, and QW arithmetic to achieve further performance improvements, and show through benchmark tests that the proposed operations can enhance performance.