# Khaled Ibrahim

Khaled Ibrahim is a scientist with the Computational Research Division. He joined Lawrence Berkeley Laboratory in Jan. 2009. He obtained his PhD in computer engineering from North Carolina State University in 2003.

His research interests are:

- Parallel Computer Architectures and High Performance Computing Machines.
- Code optimization for high performance computing and the use of accelerators for cost/power effective supercomputing.
- Virtualization and cloud computing environments for high performance computing.
- Speculation techniques in shared-memory multiprocessor system.
- Architectural support for secure computing on multiprocessor systems.
- Performance modeling and simulation acceleration.
- Power-aware scheduling of embedded applications on multiprocessor system-on-chip.

## Journal Articles

### Khaled Z. Ibrahim, Evgeny Epifanovsky, Samuel Williams, Anna I. Krylov, "Cross-scale efficient tensor contractions for coupled cluster computations through multiple programming model backends", Journal of Parallel and Distributed Computing (JPDC), February 2017, doi: 10.1016/j.jpdc.2017.02.010

### Nicholas Chaimov, Khaled Z. Ibrahim, Samuel Williams, Costin Iancu, "Reaching Bandwidth Saturation Using Transparent Injection Parallelization", International Journal of High Performance Computing Applications (IJHPCA), November 2016, doi: 10.1177/1094342016672720

### J. R. Jones, F.-H. Rouet, K. V. Lawler, E. Vecharynski, K. Z. Ibrahim, S. Williams, B. Abeln, C. Yang, C. W. McCurdy, D. J. Haxton, X. S. Li, T. N. Rescigno, "An efficient basis set representation for calculating electrons in molecules", Journal of Molecular Physics, 2016, doi: 10.1080/00268976.2016.1176262

The method of McCurdy, Baertschy, and Rescigno, J. Phys. B, 37, R137 (2004) is generalized to obtain a straightforward, surprisingly accurate, and scalable numerical representation for calculating the electronic wave functions of molecules. It uses a basis set of product sinc functions arrayed on a Cartesian grid, and yields 1 kcal/mol precision for valence transition energies with a grid resolution of approximately 0.1 bohr. The Coulomb matrix elements are replaced with matrix elements obtained from the kinetic energy operator. A resolution-of-the-identity approximation renders the primitive one- and two-electron matrix elements diagonal; in other words, the Coulomb operator is local with respect to the grid indices. The calculation of contracted two-electron matrix elements among orbitals requires only O(N log(N)) multiplication operations, not O(N^4), where N is the number of basis functions; N = n^3 on cubic grids. The representation not only is numerically expedient, but also produces energies and properties superior to those calculated variationally. Absolute energies, absorption cross sections, transition energies, and ionization potentials are reported for one- (He^+, H_2^+ ), two- (H_2, He), ten- (CH_4) and 56-electron (C_8H_8) systems.

### Nicholas Chaimov, Khaled Ibrahim, Samuel Williams, Costin Iancu, "Exploiting Communication Concurrency on High Performance Computing Systems", IJHPCA, April 17, 2015,

- Download File: thorserv2.pdf (pdf: 1.7 MB)

### Khaled Z. Ibrahim, Steven Hofmeyr, Costin Iancu, "The Case for Partitioning Virtual Machines on Manycore Architectures", IEEE TPDS, April 17, 2014,

- Download File: TPDSsubmit.pdf (pdf: 5.6 MB)

### Khaled Z Ibrahim, Kamesh Madduri, Samuel Williams, Bei Wang, Stephane Ethier, Leonid Oliker, "Analysis and optimization of gyrokinetic toroidal simulations on homogenous and heterogenous platforms", International Journal of High Performance Computing Applications (IJHPCA), July 2013, doi: 10.1177/1094342013492446

### Kamesh Madduri, Eun-Jin Im, Khaled Z. Ibrahim, Samuel Williams, Stephane Ethier, Leonid Oliker, "Gyrokinetic Particle-in-cell Optimization on Emerging Multi- and Manycore Platforms", Parallel Computing (PARCO), January 2011, 37:501 - 520, doi: 10.1016/j.parco.2011.02.001

- Download File: parco11-gtc.pdf (pdf: 2 MB)

### Khaled Z. Ibrahim, F. Bodin, "Efficient SIMDization and Data Management of the Lattice QCD Computation on the Cell Broadband Engine", Journal of Scientific computing, 2009, 17:153--172,

### Khaled Z. Ibrahim, F. Bodin, Olivier Pene, "Fine-grained Parallelization of Lattice QCD Kernel Routine on GPUs", Journal of Parallel and Distributed Computing, 2008, 68:1350-1359,

### Khaled Z. Ibrahim, Smail Niar, "Power-aware Bus Coscheduling for Periodic Realtime Applications Running on Multiprocessor SoC", Transactions on High-Performance Embedded Architectures and Compilers, 2007, 4:170--192,

## Conference Papers

### George Michelogiannakis, Khaled Z. Ibrahim, John Shalf, Jeremiah J. Wilke, Samuel Knight, Joseph P. Kenny, "APHiD: Hierarchical Task Placement to Enable a Tapered Fat Tree Topology for Lower Power and Cost in HPC Networks", 17th IEEE/ACM International Symposium on Cluster, Cloud and Grid Computing, IEEE, May 2017, LBNL 1007126,

### William Tang, Bei Wang, Stephane Ethier, Grzegorz Kwasniewski, Torsten Hoefler, Khaled Z. Ibrahim4, Kamesh Madduri, Samuel Williams, Leonid Oliker, Carlos Rosales-Fernandez, Tim Williams, "Extreme Scale Plasma Turbulence Simulations on Top Supercomputers Worldwide", Supercomputing, November 2016,

- Download File: sc16-gtcp-submit.pdf (pdf: 971 KB)

### Nicholas Chaimov, Allen Malony, Shane Canon, Costin Iancu, Khaled Ibrahim, Jay Srinivasan, "Scaling Spark on HPC Systems", High Performance and Distributed Computing (HPDC), February 5, 2016,

- Download File: spark-on-cray.pdf (pdf: 2.6 MB)

### Costin Iancu, Nicholas Chaimov, Khaled Z. Ibrahim, Samuel Williams, "Exploiting Communication Concurrency on High Performance Computing Systems", Programming Models and Applications for Multicores and Manycores (PMAM), February 2015,

- Download File: pmam15-servers.pdf (pdf: 1.2 MB)

### Khaled Z. Ibrahim, Samuel W. Williams, Evgeny Epifanovsky, Anna I. Krylov, "Analysis and Tuning of Libtensor Framework on Multicore Architectures", High Performance Computing Conference (HIPC), December 2014,

- Download File: HIPC14-libtensor.pdf (pdf: 277 KB)

### Khaled Ibrahim, Paul Hargrove, Costin Iancu, Katherine Yelick, "A Performance Evaluation of One-Sided and Two-Sided Communication Paradigms on Relaxed-Ordering Interconnect", IPDPS 2014, April 17, 2014,

### Bei Wang, Stephane Ethier, William Tang, Timothy Williams, Khaled Z. Ibrahim, Kamesh Madduri, Samuel Williams, Leonid Oliker, "Kinetic Turbulence Simulations at Extreme Scale on Leadership-Class Systems", Proceedings of the International Conference on High Performance Computing, Networking, Storage and Analysis (SC), November 2013, doi: 10.1145/2503210.2503258

- Download File: sc13gtc.pdf (pdf: 1.3 MB)

### Miao Luo, Dhabaleswar K. Panda, Khaled Z. Ibrahim, Costin Iancu, "Congestion avoidance on manycore high performance computing systems", International Conference on Supercomputing (ICS), 2012,

- Download File: ics105-luo.pdf (pdf: 1.8 MB)

### Kamesh Madduri, Khaled Ibrahim, Samuel Williams, Eun-Jin Im, Stephane Ethier, John Shalf, Leonid Oliker, "Gyrokinetic toroidal simulations on leading multi- and manycore HPC systems", Proceedings of the International Conference on High Performance Computing, Networking, Storage and Analysis (SC), January 2011, 23, doi: 10.1145/2063384.2063415

- Download File: sc11-gtc.pdf (pdf: 1.3 MB)

### Khaled Z. Ibrahim, S. Hofmeyr, Eric Roman, "Optimized Pre-Copy Live Migration for Memory Intensive Applications", The International Conference for High Performance Computing, Networking, Storage, and Analysis, 2011,

- Download File: VMMigrationsubmit.pdf (pdf: 791 KB)

### Khaled Z. Ibrahim, S. Hofmeyr, C. Iancu, "Characterizing the Performance of Parallel Applications on Multi-socket Virtual Machines", Cluster, Cloud and Grid Computing (CCGrid), 2011 11th IEEE/ACM International Symposium on, 2011, 1 -12,

- Download File: ccgrid11submit.pdf (pdf: 427 KB)

### Khaled Z. Ibrahim, Erich Strohmaier, "Characterizing the Relation Between Apex-Map Synthetic Probes and Reuse Distance Distributions", The 39th International Conference on Parallel Processing (ICPP), 2010, 353 -362,

### E. Strohmaier, S. Williams, A. Kaiser, K. Madduri, K. Ibrahim, D. Bailey, J. Demmel,, "A Kernel Testbed for Parallel Architecture, Language, and Performance Research", International Conference of Numerical Analysis and Applied Mathematics (ICNAAM), June 1, 2010, doi: 10.1063/1.3497950

### A. Kaiser, S. Williams, K. Madduri, K. Ibrahim, D. Bailey, J. Demmel, E. Strohmaier, "A Principled Kernel Testbed for Hardware/Software Co-Design Research", Proceedings of the 2nd USENIX Workshop on Hot Topics in Parallelism (HotPar), 2010,

- Download File: hotpar10-dwarfs.pdf (pdf: 128 KB)

### Khaled Z. Ibrahim, "Bridging the Gap Between Complex Software Paradigms and Power-efficient Parallel Architectures", International Conference on Green Computing, 2010, 417-424,

### Khaled Z. Ibrahim, J. Jaeger, Z. Liu, L.N. Pouchet, P. Lesnicki, L. Djoudi, D.Barthou, F. Bodin, C. Eisenbeis, G. Grosdidier, O. Pene, P. Roudeau, "Simulation of the Lattice QCD and Technological Trends in Computation", The 14th International Workshop on Compilers for Parallel Computers (CPC 09), 2009,

### Khaled Z. Ibrahim, F. Bodin, "Implementing Wilson-Dirac Operator on the Cell Broadband Engine", The 22nd ACM/SIGARCH International Conference on Supercomputing, 2008, 4--14,

### Melhem Tawk, Khaled Z. Ibrahim, Smail Niar, "Multi-granularity Sampling for Simulating Concurrent Heterogeneous Applications", CASES 08: The 2008 international conference on Compilers, architectures and synthesis for embedded systems, 2008, 217--226,

### Khaled Z. Ibrahim, F. Bodin, Olivier Pene, "Fine-grained Parallelization of Lattice QCD Kernel Routine on GPU", First Workshop on General Purpose Processing on Graphics Processing Units, 2007,

### Melhem Tawk, Khaled Z. Ibrahim, Smail Niar, "Adaptive Sampling for Efficient MPSoC Architecture Simulation", The 15th IEEE international Symposium on Modeling Analysis, and Simulation of Computer and Telecommunication Systems, 2007, 186-192,

### Melhem Tawk, Khaled Z. Ibrahim, Smail Niar, "Simulation acceleration for MPSOC Performance and Power Consumption Evaluation", Architectures and Compilers for Embedded Systems (ACES) Symposium, 2006,

### Khaled Z. Ibrahim, "Efficient Architectural Support for Secure Bus-based Shared Memory Multiprocessor", The tenth Asia-Pacific Computer Systems Architecture Conference (ACSAC 05), 2005,

### Khaled Z. Ibrahim, "Correlation between Detailed and Simplified Simulations in Studying Multiprocessor Architecture", The IEEE International Conference in Computer Design (ICCD 05), 2005, 387--392,

### Khaled Z. Ibrahim, Gregory T. Byrd, "Extending OpenMP to Support Slipstream Execution Mode", The 17th International Parallel and Distributed Processing Symposium (IPDPS 03), 2003, 36--44,

### Khaled Z. Ibrahim, Gregory T. Byrd, Eric Rotenberg, "Slipstream Execution Mode for CMP-based Multiprocessors", The 9th International Conference on High-Performance Computer Architecture (HPCA 03), 2003, 179--190,

### Khaled Z. Ibrahim, Gregory T. Byrd, "On the Exploitation of Value Prediction and Producer Identification to Reduce Barrier Synchronization Time", The 15th International Parallel and Distributed Processing Symposium (IPDPS 01), 2001, 43--50,

## Book Chapters

### Khaled Z. Ibrahim, editors: I. Ahmad, S. Ranka, "Code Development and Migration of High Performance Applications to Power-efficient Architectures", (Handbook on Energy-Aware and Green Computing:Chapman and Hall/CRC Press: 2012)

## Reports

### Khaled Z. Ibrahim, Evgeny Epifanovsky, Samuel Williams, Anna I. Krylov, "Cross-scale Efficient Tensor Contractions for Coupled Cluster Computations Through Multiple Programming Model Backends", LBNL. - Report Number: LBNL-1005853, July 1, 2016,

### A. Kaiser, S. Williams, K. Madduri, K. Ibrahim, D. Bailey, J. Demmel, E. Strohmaier, "TORCH Computational Reference Kernels: A Testbed for Computer Science Research", LBNL Technical Report, 2011, LBNL 4172E,

## Posters

### B. Wang, S. Ethier, W. Tang, K. Ibrahim, K. Madduri, S. Williams, "Advances in gyrokinetic particle in cell simulation for fusion plasmas to Extreme scale", Supercomputing (SC), 2012,

### A. Kaiser, S. Williams, K. Madduri, K. Ibrahim, D. Bailey, J. Demmel, E. Strohmaier, "A Principled Kernel Testbed for Hardware/Software Co-Design Research", Proceedings of the 2nd USENIX Workshop on Hot Topics in Parallelism (HotPar), 2010,

- Download File: hotpar10-dwarfs-poster.pdf (pdf: 679 KB)