Algebraic and Algorithmic Methods for Computing Polynomial Loop Invariants

Fuente: arXiv
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Autores principales: Bayarmagnai, Erdenebayar, Mohammadi, Fatemeh, Prébet, Rémi
Formato: Preprint
Publicado: 2024
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author Bayarmagnai, Erdenebayar
Mohammadi, Fatemeh
Prébet, Rémi
author_facet Bayarmagnai, Erdenebayar
Mohammadi, Fatemeh
Prébet, Rémi
contents Loop invariants are properties of a program loop that hold both before and after each iteration of the loop. They are often used to verify programs and ensure that algorithms consistently produce correct results during execution. Consequently, generating invariants becomes a crucial task for loops. We specifically focus on polynomial loops, where both the loop conditions and the assignments within the loop are expressed as polynomials. Although computing polynomial invariants for general loops is undecidable, efficient algorithms have been developed for certain classes of loops. For instance, when all assignments within a while loop involve linear polynomials, the loop becomes solvable. In this work, we study the more general case, where the polynomials can have arbitrary degrees. Using tools from algebraic geometry, we present two algorithms designed to generate all polynomial invariants within a given vector subspace, for a branching loop with nondeterministic conditional statements. These algorithms combine linear algebraic subroutines with computations on polynomial ideals. They differ depending on whether the initial values of the loop variables are specified or treated as parameters. Additionally, we present a much more efficient algorithm for generating polynomial invariants of a specific form, applicable to all initial values. This algorithm avoids expensive ideal computations.
format Preprint
id arxiv_https___arxiv_org_abs_2412_14043
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Algebraic and Algorithmic Methods for Computing Polynomial Loop Invariants
Bayarmagnai, Erdenebayar
Mohammadi, Fatemeh
Prébet, Rémi
Symbolic Computation
Programming Languages
Algebraic Geometry
Loop invariants are properties of a program loop that hold both before and after each iteration of the loop. They are often used to verify programs and ensure that algorithms consistently produce correct results during execution. Consequently, generating invariants becomes a crucial task for loops. We specifically focus on polynomial loops, where both the loop conditions and the assignments within the loop are expressed as polynomials. Although computing polynomial invariants for general loops is undecidable, efficient algorithms have been developed for certain classes of loops. For instance, when all assignments within a while loop involve linear polynomials, the loop becomes solvable. In this work, we study the more general case, where the polynomials can have arbitrary degrees. Using tools from algebraic geometry, we present two algorithms designed to generate all polynomial invariants within a given vector subspace, for a branching loop with nondeterministic conditional statements. These algorithms combine linear algebraic subroutines with computations on polynomial ideals. They differ depending on whether the initial values of the loop variables are specified or treated as parameters. Additionally, we present a much more efficient algorithm for generating polynomial invariants of a specific form, applicable to all initial values. This algorithm avoids expensive ideal computations.
title Algebraic and Algorithmic Methods for Computing Polynomial Loop Invariants
topic Symbolic Computation
Programming Languages
Algebraic Geometry
url https://arxiv.org/abs/2412.14043