3,053 research outputs found
Block preconditioners for linear systems in interior point methods for convex constrained optimization
No full textParallel Newton methods for sparse systems of nonlinear equations
No full textA parallel code based on Cimmino-like preconditioner is developed for the solution of the Newton linearized system
Truncated block Newton and quasi-Newton methods for sparse systems of nonlinear equations. Experiments on parallel platforms
No full textIn this paper we give the results found in solving consistent
sparse systems of nonlinear equations
by an inexact Newton and Quasi-Newton method
both combined with a block iterative row-projection linear solver of Cimmino-type.
A simple partitioning of the Jacobian matrix was used for solving two
nonlinear test problems,
that is a tridiagonal problem of size n = 131072
and a nonlinear Poisson problem.
The results are obtained
on the CRAY T3E installed at CINECA (Bologna, Italy) with 32 nodes.
The Fortran code runs under MPI implementation
La querelle sui Comitati Unici di Garanzia negli Atenei
No full textIl saggio affronta il tema dei CUG nella università, nell'ambito della complessiva riforma della governance degli atenei e delle politiche di reclutament
An assessment of the impact of possible CAP reform scenarios on Romanian agriculture
No full textUsing a simplified model, with key-variable the prices of two different possible scenarios of CAP reform after 2013 (moderate and radical), this paper present a comparison between the price effects of implementation of each reform scenario at 2015 horizon on Romanian agriculture. This short analysis shows that, under the presented hypotheses, the net welfare effect, due to the price changes, for the selected products, is positive in both reform scenarios, yet greater in the case of the radical reform. Integrated in the large context of Romanian development, it seems that the influence of CAP reform upon agriculture and rural areas will be most likely a gradual one: an interpenetration between the two scenarios is foreseeable, starting with the moderate reform that will dominate the period around 2013, the reform measures acquiring a more radical character afterwards.CAP reform, Romania, welfare effects, Agricultural and Food Policy,
Inexact constraint preconditioners for linear systems arising in interior point methods
No full textInterior-point methods, Iterative solvers, Preconditioners, Approximate Jacobian,
Rich, Sturmian, and trapezoidal words
No full textIn this paper we explore various interconnections between rich words, Sturmian words, and trapezoidal words. Rich words, first introduced by the second and third authors together with J. Justin and S. Widmer, constitute a new class of finite and infinite words characterized by having the maximal number of palindromic factors. Every finite Sturmian word is rich, but not conversely. Trapezoidal words were first introduced by the first author in studying the behavior of the subword complexity of finite Sturmian words. Unfortunately this property does not characterize finite Sturmian words. In this note we show that the only trapezoidal palindromes are Sturmian. More generally we show that Sturmian palindromes can be characterized either in terms of their subword complexity (the trapezoidal property) or in terms of their palindromic complexity. We also obtain a similar characterization of rich palindromes in terms of a relation between palindromic complexity and subword complexity
Inexact Quasi-Newton methods for sparse systems of nonlinear equations
No full textIn this paper, we present the results obtained by solving consistent sparse systems of n nonlinear equations F(x) = 0, by a Quasi-Newton method combined with a p block iterative row-projection linear solver of Cimmino type, 1 less than or equal to p << n. Under weak regularity conditions for F, it is proved that this Inexact Quasi-Newton method has a local, linear convergence in the energy norm induced by the preconditioned matrix HA, where A is an initial guess of the Jacobian matrix, and it may converge too superlinearly. The matrix H = [A(1)(+),...,A(i)(+),...,A(p)(+)], where A(i)(+) = A(i)(T)(A(i)A(i)(T))(-1) is the Moore-Penrose pseudo-inverse of the mi x n block A(i), the preconditioner. A simple partitioning of the Jacobian matrix was used for solving a set of nonlinear test problems with sizes ranging from 1024 to 131 072 on the CRAY T3E under the MPI environmen
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