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FloVer - A Certificate Checker for Roundoff Error Bounds

This is a copy of the FloVer code at [https://gitlab.mpi-sws.org/AVA/FloVer]

CertificateCheckerScript.sml: This file contains the HOL4 implementation of the certificate checker as well as its soundness proof. The checker is a composition of the range analysis validator and the error bound validator. Running this function on the encoded analysis result gives the desired theorem as shown in the soundness theorem.

CertificateGeneratorScript.sml: A simple, unverified generator for certificates. To be used in conjunction with the certificate checker to first analyze a kernel and then validate the analysis result

EnvironmentsScript.sml: An inductive relation relating real-numbered environments with an environment with "errors", i.e. where variables are bound to finite-precision values

ErrorBoundsScript.sml: Proofs of general bounds on the error of arithmetic Expressions. This shortens soundness proofs later. Bounds are exprlained in section 5, Deriving Computable Error Bounds

ErrorIntervalInferenceScript.sml: This file contains the HOL4 implementation of the error bound validator as well as its soundness proof. The function validErrorbound is the Error bound validator from the certificate checking process. Under the assumption that a valid range arithmetic result has been computed, it can validate error bounds encoded in the analysis result. The validator is used in the file CertificateChecker.v to build the complete checker.

ErrorValidationScript.sml: This file contains the HOL4 implementation of the error bound validator as well as its soundness proof. The function validErrorbound is the Error bound validator from the certificate checking process. Under the assumption that a valid range arithmetic result has been computed, it can validate error bounds encoded in the analysis result. The validator is used in the file CertificateChecker.v to build the complete checker.

FPRangeValidatorScript.sml: Floating-Point range validator

IEEE_connectionScript.sml: Connect FloVer's idealized machine semantics to 64-bit IEEE-754 floating-point semantics

Infra: Infrastructural lemmas and formalizations for FloVer

IntervalArithScript.sml: Formalization of real valued interval arithmetic Used in soundness proofs for error bound validator.

IntervalValidationScript.sml: Interval arithmetic checker and its soundness proof. The function validIntervalbounds checks wether the given analysis result is a valid range arithmetic for each sub term of the given exprression e. The computation is done using our formalized interval arithmetic. The function is used in CertificateChecker.v to build the full checker.

RealIntervalInferenceScript.sml: Implement a trusted, unverified inferencer for real range intervals. The inferred, returned maps should be run through the certificate checker

RealRangeArithScript.sml: Recursive correctness predicate for a range analysis with some supporting theorems

TypeValidatorScript.sml: Simple Type Inference algorithm with correctness proof to infer machine type assignments for FloVer's input expressions

semantics: Formalization of idealized semantics of FloVer that handle both real-numbered semantics and finite-precision semantics.

sqrtApproxScript.sml: Simple approximation of sqrt as it is not computable in HOL4 using newton iterations. As the iteration may fail, the process "self-validates", checkign that the result is an over/under-approximation of the real sqrt

ssaPrgsScript.sml: We define a pseudo SSA predicate. The formalization is similar to the renamedApart property in the LVC framework by Schneider, Smolka and Hack (http://dblp.org/rec/conf/itp/SchneiderSH15) Our predicate is not as fully fledged as theirs, but we especially borrow the idea of annotating the program with the predicate with the set of free and defined variables