RobustArithmetic 0.2.0

Version 0.1.1 was never published; its changes are included here and this release is described against 0.1.0.

Correctly rounded kernels included in the package

• The fast level evaluates exp, log, sin, cos, tan, sinh, cosh, tanh, expm1, log1p, log2, log10, asin, acos and atan with fifteen CORE-MATH binary64 kernels compiled into the package (MIT license, pinned commit 1ab68b70b90f807fd2bc9cf20ec295d49ae09592), and sqrt with the hardware square root. Correct rounding of these functions no longer depends on the math library of the platform. The package now contains compiled code; origin, copyright holders, local changes and license texts are listed in inst/COPYRIGHTS.
• The two operations on which correct rounding of those kernels depends, fma and roundeven, come from src/ra_portable_math.h: the FMA instruction where the compiler guarantees it, otherwise the fma of musl (MIT) with an exact final scaling, and a bitwise roundeven everywhere.
• Every fast-level enclosure is widened by a slack of two outward steps for all sixteen functions, from the pre-registered formula ceiling(2e + 1) with the half-unit error bound e = 0.5 of correct rounding. Fast-level provenance remains measured.
• ra_measure_library_error() measures the included route against MPFR.

Safeguards

• At load, 128 sentinels (eight hard cases per function, with values computed independently with MPFR) are compared bit for bit with the included route.
• New exported function ra_fast_level_status() reports whether the fast level is degraded, the reason, the sentinel check and the first-use audit.
• When the fast level is degraded, the first affected result emits a single warning of class ra_fast_level_unsafe and is recomputed at the rigorous level with theorem provenance; without Rmpfr, each affected evaluation signals an error of that class. The behaviour is the same with library() and with RobustArithmetic::.
• A healthy session prints no startup message.
• ra_environment_anchor() and the environment anchor are removed.

Printing and solving

• format() of an interval certifies that the printed decimal bounds contain the binary64 endpoints without relying on as.numeric(), also where R has no extended-precision long double, and stops with an error instead of printing a looser bound. In the measured benchmark of 1,000 random intervals, median formatting time increased by 54%.
• ra_solve() derives verdict provenance from the evaluations supporting each certificate. Printed cards use the label verdict provenance, and summaries use Theorem provenance for every verdict.

Tests and build

• Tests of the fast-level machinery hold the level open for their own block, so that they assert the code and not the math library of the machine; the degradation rules are tested separately.
• The check that Rmpfr refuses trigamma() runs in a child R process.
• VignetteBuilder declares knitr, rmarkdown.

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