12 research outputs found
Parallelization of Modular Algorithms
In this paper we investigate the parallelization of two modular algorithms.
In fact, we consider the modular computation of Gr\"obner bases (resp. standard
bases) and the modular computation of the associated primes of a
zero-dimensional ideal and describe their parallel implementation in SINGULAR.
Our modular algorithms to solve problems over Q mainly consist of three parts,
solving the problem modulo p for several primes p, lifting the result to Q by
applying Chinese remainder resp. rational reconstruction, and a part of
verification. Arnold proved using the Hilbert function that the verification
part in the modular algorithm to compute Gr\"obner bases can be simplified for
homogeneous ideals (cf. \cite{A03}). The idea of the proof could easily be
adapted to the local case, i.e. for local orderings and not necessarily
homogeneous ideals, using the Hilbert-Samuel function (cf. \cite{Pf07}). In
this paper we prove the corresponding theorem for non-homogeneous ideals in
case of a global ordering.Comment: 16 page
An algorithm for primary decomposition in polynomial rings over the integers
We present an algorithm to compute a primary decomposition of an ideal in a
polynomial ring over the integers. For this purpose we use algorithms for
primary decomposition in polynomial rings over the rationals resp. over finite
fields, and the idea of Shimoyama-Yokoyama resp. Eisenbud-Hunecke-Vasconcelos
to extract primary ideals from pseudo-primary ideals. A parallelized version of
the algorithm is implemented in SINGULAR. Examples and timings are given at the
end of the article.Comment: 8 page
Parallel algorithms for normalization
Given a reduced affine algebra A over a perfect field K, we present parallel
algorithms to compute the normalization \bar{A} of A. Our starting point is the
algorithm of Greuel, Laplagne, and Seelisch, which is an improvement of de
Jong's algorithm. First, we propose to stratify the singular locus Sing(A) in a
way which is compatible with normalization, apply a local version of the
normalization algorithm at each stratum, and find \bar{A} by putting the local
results together. Second, in the case where K = Q is the field of rationals, we
propose modular versions of the global and local-to-global algorithms. We have
implemented our algorithms in the computer algebra system SINGULAR and compare
their performance with that of the algorithm of Greuel, Laplagne, and Seelisch.
In the case where K = Q, we also discuss the use of modular computations of
Groebner bases, radicals, and primary decompositions. We point out that in most
examples, the new algorithms outperform the algorithm of Greuel, Laplagne, and
Seelisch by far, even if we do not run them in parallel.Comment: 19 page
Parameter identification for soil simulation based on the discrete element method and application to small scale shallow penetration tests
The Discrete Element Method (DEM) is well-established and widely used in soil-tool interaction related applications. As for all simulation tools, a proper calibration of the model parameters is crucial. In this contribution, we present the parametrization procedure of the DEM software GRAnular Physics Engine (GRAPE), developed and implemented at Fraunhofer ITWM, and attempt to use two parametrized soil samples for the simulation of small scale shallow penetration tests. The results are compared to laboratory measurements
Triaxial compression and direct shear tests in the parametrization of soil modeled via the Discrete Element Method
Investigation in the parametrization of soil modeled with DEM based on measurements in triaxial compression and direct shear tests
Groebner bases of symmetric ideals
In this article we present two new algorithms to compute the Groebner basis
of an ideal that is invariant under certain permutations of the ring variables
and which are both implemented in SINGULAR (cf. [DGPS12]). The first and major
algorithm is most performant over finite fields whereas the second algorithm is
a probabilistic modification of the modular computation of Groebner bases based
on the articles by Arnold (cf. [A03]), Idrees, Pfister, Steidel (cf. [IPS11])
and Noro, Yokoyama (cf. [NY12], [Y12]). In fact, the first algorithm that
mainly uses the given symmetry, improves the necessary modular calculations in
positive characteristic in the second algorithm. Particularly, we could, for
the first time even though probabilistic, compute the Groebner basis of the
famous ideal of cyclic 9-roots (cf. [BF91]) over the rationals with SINGULAR.Comment: 17 page
About the computation of the signature of surface singularities z^N+g(x,y)=0
In this article we describe our experiences with a parallel
SINGULAR-implementation of the signature of a surface singularity defined by
z^N+g(x,y)=0.Comment: 6 page
Parameter identification for soil simulation based on the discrete element method and application to small scale shallow penetration tests
The Discrete Element Method (DEM) is well-established and widely used in soil-tool interaction related applications. As for all simulation tools, a proper calibration of the model parameters is crucial. In this contribution, we present the parametrization procedure of the DEM software GRAnular Physics Engine (GRAPE), developed and implemented at Fraunhofer ITWM, and attempt to use two parametrized soil samples for the simulation of small scale shallow penetration tests. The results are compared to laboratory measurements