Short bio

I prepared my Ph.D. at Inria-Paris and Sorbonne University (Paris — VI). It was funded by TOTAL S.A. From January 2019 to July 2020 I was a Max Planck Society postdoctoral research fellow in the NLMA team in the CSC group. Starting from August 2020, I hold a research position at the Computational Mathematics Group, STFC, UKRI.


Research items

  • High performance computing

  • Numerical linear algebra

  • Tensor methods

  • Krylov subspace methods

  • Domain decomposition methods


  • H. Al Daas, P. Jolivet

A Robust Algebraic Multilevel Domain Decomposition Preconditioner For Sparse Symmetric Positive Definite Matrices. 2021


  • H. Al Daas, P. Jolivet, J. Scott.

A Robust Algebraic Domain Decomposition Preconditioner for Sparse Normal Equations. 2021.

PDF. Code for reproducing the results available here, PETSc interface through the HPDDM package, PCHPDDM.

  • H. Al Daas, G. Ballard, P. Benner.

Parallel Algorithms for Tensor Train Arithmetic. 2020.


  • P. Goyal, H. Al Daas, P. Benner.

Low-Rank and Total Variation Regularization and Its Application to Image Recovery. 2020.



  • H. Al Daas, T. Rees, J. Scott.

Two-level Nyström--Schur preconditioner for sparse symmetric positive definite matrices. 2021.

Accepted in SIAM Journal for Scientific Computing, in press. PDF.

  • H. Al Daas, L. Grigori, P. Jolivet, P. H. Tournier.

A Multilevel Schwarz Preconditioner Based on a Hierarchy of Robust Coarse Spaces. 2021.

SIAM Journal for Scientific Computing. PDF.

Code for reproducing the results available here, PETSc interface through the HPDDM package, PCHPDDM.

  • H. Al Daas, L. Grigori, P. Henon, P. Ricoux.

Recycling Krylov Subspaces and Truncating Deflation Subspaces for Solving Sequence of Linear Systems. 2021

ACM Transactions on Mathematical Software. PDF.

  • H. Al Daas.

Solving linear systems arising from reservoirs modeling. Ph.D. thesis, PDF, bibtex.

  • H. Al Daas, L. Grigori.

A Class of Efficient Locally Constructed Preconditioners Based on Coarse Spaces. 2019.

SIAM Journal on Matrix Analysis and Applications. PDF.

  • H. Al Daas, L. Grigori, P. Hénon, Ph. Ricoux.

Enlarged GMRES for solving linear systems with one or multiple right-hand sides. 2018.

IMA Journal. PDF.

Selected talks

  • Communication-avoiding orthogonalization algorithm for tensor trains, GAMM ANLA 2019, Chemnitz, Germany

  • Efficient algebraic coarse spaces, Sparse Days 2018, Toulouse, France

  • Deflation subspaces and GMRES for solving a sequence of linear systems, PMAA18, Zurich, Switzerland

  • Enlarged GMRES for reducing communication, SIAM PP18, MS 28, Tokyo, Japan

  • Krylov subspace methods and deflation strategies, Junior Seminar at INRIA- Paris, France

  • Enlarged GMRES for a sequence of linear systems, MATHIAS18, Paris, France

  • Enlarged GMRES, SIAM CSE17, MS254, Atlanta, USA

  • GMRES based on enlarged Krylov subspaces, SIAM PP16, MS12, Paris, France

Research stays

  • CSTJF, centre scientifique TOTAL, Pau, collaboration with Pascal Hénon (Jan.-Feb. 2018)

  • CEMRACS, CIRM, Marseille, 6-week summer school (Jul.-Aug. 2016)

  • University of California, Berkeley, BeBOP group. Five-month visit in James Demmel’s research group (Jan.-May 2016)


  • Journal(s)

  • Conference(s)

    • PASC

    • EuroPar


  • Co-developer

    • CPaLAMeM: C Parallel Linear Algebra Memory Management in PreAlps package (several linear solvers and preconditioners)

  • Developer

    • cTT, pcTT: C and C-MPI implementation of TT tensor arithmetic operations

    • EGMRES, GMRES-MDR and Block GMRES-MDR: C-MPI implementation of enlarged GMRES with deflated restarting, GMRES with Modified Deflated Restart, and Block GMRES-MDR with different variants of deflation strategies


  • 2019 Numerical Linear Algebra, Bachelor level. Teaching Assistant, Otto von Guericke University, Magdeburg, Germany

  • 2017 Calculus, Introduction to Analysis for first year students. Teaching Assistant, UPMC, Paris, France

  • 2015 Numerical analysis, Scientific computation for third year students. Teaching Assistant, ENSAE, Paris, France