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- Emanuel H. Rubensson, Anders M. N. Niklasson
- SIAM J. Scientific Computing
- 2014

- Elias Rudberg, Emanuel H Rubensson, Paweł Sałek
- Journal of chemical theory and computation
- 2011

We present a complete linear scaling method for hybrid Kohn-Sham density functional theory electronic structure calculations and demonstrate its performance. Particular attention is given to the linear scaling computation of the Kohn-Sham exchange-correlation matrix directly in sparse form within the generalized gradient approximation. The described method… (More)

- Elias Rudberg, Emanuel H Rubensson, Paweł Sałek
- The Journal of chemical physics
- 2008

We present an implementation of a set of algorithms for performing Hartree-Fock calculations with resource requirements in terms of both time and memory directly proportional to the system size. In particular, a way of directly computing the Hartree-Fock exchange matrix in sparse form is described which gives only small addressing overhead. Linear scaling… (More)

- Emanuel H. Rubensson, Elias Rudberg
- Journal of Computational Chemistry
- 2011

The performance of linear-scaling electronic structure calculations depends critically on matrix sparsity. This article gives an overview of different strategies for removal of small matrix elements, with emphasis on schemes that allow for rigorous control of errors. In particular, a novel scheme is proposed that has significantly smaller computational… (More)

- Emanuel H Rubensson, Elias Rudberg, Paweł Sałek
- The Journal of chemical physics
- 2008

Density matrix purification, although being a powerful tool for linear scaling construction of the density matrix in electronic structure calculations, has been limited by uncontrolled error accumulation. In this article, a strategy for the removal of small matrix elements in density matrix purification is proposed with which the forward error can be… (More)

- Emanuel H Rubensson
- Journal of chemical theory and computation
- 2011

As it stands, density matrix purification is a powerful tool for linear scaling electronic structure calculations. The convergence is rapid and depends only weakly on the band gap. However, as will be shown in this letter, there is room for improvements. The key is to allow for nonmonotonicity in the recursive polynomial expansion. On the basis of this… (More)

- Elias Rudberg, Emanuel H Rubensson
- Journal of physics. Condensed matter : an…
- 2011

Purification and minimization methods for linear scaling computation of the one-particle density matrix for a fixed Hamiltonian matrix are compared. This is done by considering the work needed by each method to achieve a given accuracy in terms of the difference from the exact solution. Numerical tests employing orthogonal as well as non-orthogonal versions… (More)

- Emanuel H Rubensson, Sara Zahedi
- The Journal of chemical physics
- 2008

Density matrix purification, is in this work, used to facilitate the computation of eigenpairs around the highest occupied and the lowest unoccupied molecular orbitals (HOMO and LUMO, respectively) in electronic structure calculations. The ability of purification to give large separation between eigenvalues close to the HOMO-LUMO gap is used to accelerate… (More)

- Emanuel H Rubensson, Nicolas Bock, Erik Holmström, Anders M N Niklasson
- The Journal of chemical physics
- 2008

A recursive algorithm for the inverse factorization S(-1)=ZZ(*) of Hermitian positive definite matrices S is proposed. The inverse factorization is based on iterative refinement [A.M.N. Niklasson, Phys. Rev. B 70, 193102 (2004)] combined with a recursive decomposition of S. As the computational kernel is matrix-matrix multiplication, the algorithm can be… (More)

- Emanuel H. Rubensson, Elias Rudberg
- Parallel Computing
- 2014

We propose Chunks and Tasks, a parallel programming model built on abstractions for both data and work. The application programmer specifies how data and work can be split into smaller pieces, chunks and tasks, respectively. The Chunks and Tasks library maps the chunks and tasks to physical resources. In this way we seek to combine user friendliness with… (More)