Sökning: "eigenvectors"

Visar resultat 1 - 5 av 32 avhandlingar innehållade ordet eigenvectors.

  1. 1. Matrix Algebra for Quantum Chemistry

    Författare :Emanuel H. Rubensson; Pawel Salek; Stefan Goedecker; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; linear scaling; reduced complexity; electronic structure; density functional theory; Hartree-Fock; density matrix purification; congruence transformation; inverse factorization; eigenvalues; eigenvectors; numerical linear algebra; occupied subspace; canonical angles; invariant subspace; Theoretical chemistry; Teoretisk kemi;

    Sammanfattning : This thesis concerns methods of reduced complexity for electronic structure calculations.  When quantum chemistry methods are applied to large systems, it is important to optimally use computer resources and only store data and perform operations that contribute to the overall accuracy. LÄS MER

  3. 2. An implementation of a parallel rational Krylov algorithm

    Författare :Daniel Skoogh; Chalmers tekniska högskola; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; paralell; shift; sparse; Krylov; Arnoldi; invert; eigenvalues; eigenvectors; rational;

    Sammanfattning : .... LÄS MER

  4. 3. Krylov Subspace Methods for Linear Systems, Eigenvalues and Model Order Reduction

    Författare :Daniel Skoogh; Göteborgs universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; eigenvalues; eigenvectors; sparse; parallel; rational; Krylov; shift; invert; Arnoldi; linear systems; iterative; model; reduction; passive; 65F15; 65F50; 65Y05; 65F10; 93A30; 93B40; rational;

    Sammanfattning : New variants of Krylov subspace methods for numerical solution of linear systems, eigenvalue, and model order reduction problems are described. A new method to solve linear systems of equations with several right-hand sides is described. LÄS MER

  5. 4. Efficient Density Matrix Methods for Large Scale Electronic Structure Calculations

    Författare :Anastasia Kruchinina; Emanuel H. Rubensson; Elias Rudberg; David Bowler; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; electronic structure; linear scaling; density matrix; density functional theory; Hartree-Fock; recursive polynomial expansion; density matrix purification; eigenvectors; molecular orbitals; stopping criteria; inverse factorization; matrix sparsity; parallelization; Scientific Computing; Beräkningsvetenskap;

    Sammanfattning : Efficient and accurate methods for computing the density matrix are necessary to be able to perform large scale electronic structure calculations. For sufficiently sparse matrices, the computational cost of recursive polynomial expansions to construct the density matrix scales linearly with increasing system size. LÄS MER

  7. 5. Improving the efficiency of eigenvector-related computations

    Författare :Angelika Beatrix Schwarz; Lars Karlsson; Bo Kågström; Carl Christian Kjelgaard Mikkelsen; Miroslav Tůma; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; high-performance computing; standard non-symmetric eigenvalue problem; triangular Sylvester equation; tiled algorithms; task parallelism;

    Sammanfattning : An effective strategy in dense linear algebra is the design of algorithms as tiled algorithms. Tiled algorithms that express the bulk of the computation as matrix-matrix operations (level-3 BLAS) have proven successful in achieving high performance on cache-based architectures. LÄS MER