# 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**.

2020: Computational mathematics researcher at

**STFC, Rutherford Appleton Laboratory**2019-2020: Postdoctoral research fellow at Max Planck Institute for Dynamics of Complex Technical Systems

2015-2018: PhD in Applied Mathematics at Inria-Paris and Sorbonne University (Paris — VI)

2012-2014: Master in Fundamental and Applied Mathematics at Paris-Sud University (Paris — XI)

# Research

## Research items

High performance computing

Numerical linear algebra

Tensor methods

Krylov subspace methods

Domain decomposition methods

## Preprint(s)

H. Al Daas, T. Rees, J. Scott.

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

**PDF**.

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

**Parallel Algorithms for Tensor Train Arithmetic. **2020.

** ****PDF**.

P. Goyal, H. Al Daas, P. Benner.

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

**PDF****,**

## Publications

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

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

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

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. **2020

Accepted in ACM Transactions on Mathematical Software. **PDF****, ****bibtex**.

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**)

## Reviewer

**Journal(s)**Parallel computing, Certificate

**Conference(s)**PASC

EuroPar

## Software

**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

## Teaching

**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