In this paper, we present a parallel quasi-Chebyshev acceleration applied to the nonoverlapping multisplitting iterative method for the linear systems when the coefficient matrix is either an H-matrix or a symmetric positive definite matrix. First, m parallel iterations are implemented in m different processors. Second, based on l1-norm or l2-norm, the m optimization models are parallelly treat...

In this paper, we study subspace embedding problem and obtain the following results: 1. We extend the results of approximate matrix multiplication from the Frobenius norm to the spectral norm. Assume matrices A and B both have at most r stable rank and r̃ rank, respectively. Let S be a subspace embedding matrix with l rows which depends on stable rank, then with high probability, we have ‖ASSB−A...

We propose a block Davidson-type subspace iteration using Chebyshev polynomial filters for large symmetric/hermitian eigenvalue problem. The method consists of three essential components. The first is an adaptive procedure for constructing efficient block Chebyshev polynomial filters; the second is an inner–outer restart technique inside a Chebyshev–Davidson iteration that reduces the computati...

We extend a result of Ramaré and Rumely, 1996, about the Chebyshev function θ in arithmetic progressions. We find a map ε(x) such that | θ(x; k, l)− x/φ(k) |< xε(x) and ε(x) = O ( 1 lna x ) (∀a > 0), whereas ε(x) is a constant. Now we are able to show that, for x > 1531, | θ(x; 3, l)− x/2 |< 0.262 x lnx and, for x > 151, π(x; 3, l) > x 2 lnx .

We extend a result of Ramaré and Rumely, 1996, about the Chebyshev function θ in arithmetic progressions. We find a map ε(x) such that | θ(x; k, l)− x/φ(k) |< xε(x) and ε(x) = O ( 1 lna x ) (∀a > 0), whereas ε(x) is a constant. Now we are able to show that, for x > 1531, | θ(x; 3, l)− x/2 |< 0.262 x lnx and, for x > 151, π(x; 3, l) > x 2 lnx .

We extend a result of Ramaré & Rumely, 1996 [3] about Chebyshev function θ in arithmetic progressions. We find a map ε(x) such that | θ(x; k, l) − x/φ(k) |< xε(x) and ε(x) = O ( 1 lna x ) (∀a > 0) whereas ε(x) is a constant in [3]. Now we are able to show that | θ(x; 3, l)− x/2 |< 0.262 x lnx and, for x > 151, π(x; 3, l) > x 2 lnx .

Solving the Kohn-Sham eigenvalue problem constitutes the most computationally expensive part in self-consistent density functional theory (DFT) calculations. In a previous paper, we have proposed a nonlinear Chebyshev-filtered subspace iteration method, which avoids computing explicit eigenvectors except at the first self-consistent-field (SCF) iteration. The method may be viewed as an approach...

We present a spectrum-splitting approach to conduct all-electron Kohn-Sham density functional theory (DFT) calculations by employing Fermi-operator expansion of the Kohn-Sham Hamiltonian. The proposed approach splits the subspace containing the occupied eigenspace into a core-subspace, spanned by the core eigenfunctions, and its complement, the valence-subspace, and thereby enables an efficient...

Let X be a Banach space, let φ denote the usual Kuratowski measure of noncompactness, and let kX (ε) = sup r (D) where r (D) is the Chebyshev radius of D and the supremum is taken over all closed convex subsets D of X for which diam (D) = 1 and φ (D) ≥ ε. The space X is said to have φ-uniform normal structure if kX (ε) < 1 for each ε ∈ (0, 1) . It is shown that this concept, which lies strictly...

A subspace-evasive set over a field F is a subset of F that has small intersection with any low-dimensional affine subspace of F. Interest in subspace evasive sets began in the work of Pudlák and Rödl (Quaderni di Matematica 2004). More recently, Guruswami (CCC 2011) showed that obtaining such sets over large fields can be used to construct capacity-achieving list-decodable codes with a constan...