Twofold exp and log

Abstract: This article is about twofold arithmetic. Here I introduce algorithms and experimental code for twofold variant of C/C++ standard functions exp(x) and log(y), and expm1(x) and log1p(y). Twofold function z₀+z₁≈f(x₀+x₁) is nearly 2x-precise so can assess accuracy of standard one. Performance allows assessing on-fly: twofold texp(x) over double is ~10x times faster than expq(x) by GNU quadmath.

2015 (C) Evgeny Latkin, Free for academic and non-commercial

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Text also uploaded to arXiv, link: http://arxiv.org/abs/1502.05216