Mohammad Ansari

Research Associate

Room number: IT-302
email: ansari +=at=+ cs.man.ac.uk
Tel.: +44 161 275 3531
Fax: +44 161 275 6204

Background

In October 2008, I joined as a Research Associate on the JAMAICA Project, supervised by Prof. Ian Watson. Prior to this appointment, I was a Ph.D. student on the JAMAICA project, for which I recently passed my oral defense. The JAMAICA Project has a diverse research profile, and I currently study Transactional Memory (TM) [1] [2].

Transactional Memory

NOTE: I am currently expanding the areas of TM that I investigate. Below is a description of my research focus during my Ph.D.

My research focuses on contention management [3][4] in Software TM (STM), although my approach is different from the traditional idea of acting only upon conflict detection. My primary research platform is the popular Java-based STM implementation DSTM2 [5], a highly modular, robust, and easy to use/develop TM implementation, although I also use RSTM [6] and TL2-x86 [7].

I have made the first use of control theory to dynamically change the number of concurrently executing threads with respect to the transaction commit rate, resulting in significant resource usage reduction with little to no performance degradation [8]. I have extended this work with an advanced control algorithm that improves resource usage efficiency across a larger number of benchmarks, whilst also being more robust to measurement disturbances, and showing excellent control characteristics when analyzed using conventional control theory metrics [9].

I have also constructed a technique called steal-on-abort [10], which reorders transactions at runtime to improve the performance of TM applications. The key benefit of steal-on-abort is that it is completely transparent, i.e. requires no offline processing, or explicit input from the programmer, and it only adds overhead when aborts occur.

Research Interests

Although I take an interest in all things related to transactional memory, my broader research interests span the area of high performance computing, and concurrent programming in particular. As a result, I am interested in supporting concurrency through programming models, algorithms, compilers, runtimes, and processor architecture. I believe this is an exciting area of research, given that multi-cores promise to make parallel processing ubiquitous.

Publications

• On the Performance of Contention Managers for Complex Transactional Memory Benchmarks
  Mohammad Ansari, Christos Kotselidis, Mikel Luján, Chris Kirkham and Ian Watson
  In the 8th International Symposium on Parallel and Distributed Computing (ISPDC'09), July 2009.
  [PDF] [BibTeX]
• Transaction Reordering to Reduce Aborts in Software Transactional Memory
  Mohammad Ansari, Mikel Luján, Christos Kotselidis, Kim Jarvis, Chris Kirkham and Ian Watson
  In Transactions on High Performance and Embedded Architectures and Compilers (HIPEAC Journal), 2009.
  [PDF] [BibTeX]
• Profiling Transactional Memory Applications
  Mohammad Ansari, Kim Jarvis, Christos Kotselidis, Mikel Luján, Chris Kirkham and Ian Watson
  In the 17th Euromicro International Conference on Parallel, Distributed, and Network-based Processing (PDP'09), February 2009.
  [PDF] [BibTeX]
• Steal-on-abort: Improving Transactional Memory Performance through Dynamic Transaction Reordering
  Mohammad Ansari, Mikel Luján, Christos Kotselidis, Kim Jarvis, Chris Kirkham and Ian Watson
  In the 4th International Conference on High Performance and Embedded Architectures and Compilers (HIPEAC'09), January 2009.
  [PDF] [BibTeX]
• Investigating Contention Management for Complex Transactional Memory Benchmarks
  Mohammad Ansari, Christos Kotselidis, Mikel Luján, Chris Kirkham and Ian Watson
  In the 2nd Workshop on Programmability Issues for Multi-Core Computers (MULTIPROG'09), January 2009.
  [PDF] [BibTeX]
• Robust Adaptation to Available Parallelism in Transactional Memory Applications
  Mohammad Ansari, Mikel Luján, Christos Kotselidis, Kim Jarvis, Chris Kirkham and Ian Watson
  In Transactions on High Performance and Embedded Architectures and Compilers (HIPEAC Journal), 2008.
  [PDF] [BibTeX]
• DiSTM: A Software Transactional Memory Framework for Clusters
  Christos Kotselidis, Mohammad Ansari, Kim Jarvis, Mikel Luján, Chris Kirkham and Ian Watson
  In the 37th IEEE International Conference on Parallel Processing (ICPP'08), September 2008.
  [PDF] [BibTeX]
• Advanced Concurrency Control for Transactional Memory using Transaction Commit Rate
  Mohammad Ansari, Christos Kotselidis, Kim Jarvis, Mikel Luján, Chris Kirkham and Ian Watson
  In the 14th European Conference on Parallel Processing (EUROPAR'08), August 2008.
  [PDF] [BibTeX]
• Steal-on-abort: Dynamic Transaction Reordering to Reduce Conflicts in Transactional Memory
  Mohammad Ansari, Mikel Luján, Christos Kotselidis, Kim Jarvis, Chris Kirkham and Ian Watson
  In the Workshop on Software and Hardware Challenges of Manycore Platforms (SHCMP'08), June 2008.
  [PDF] [BibTeX]
• Lee-TM: A Non-trivial Benchmark for Transactional Memory
  Mohammad Ansari, Christos Kotselidis, Kim Jarvis, Mikel Luján, Chris Kirkham and Ian Watson
  In the 8th International Conference on Algorithms and Architectures for Parallel Processing (ICA3PP'08), June 2008.
  [PDF] [BibTeX] [Code]
• Investigating Software Transactional Memory on Clusters
  Christos Kotselidis, Mohammad Ansari, Kim Jarvis, Mikel Luján, Chris Kirkham and Ian Watson
  In the 10th International Workshop on Java and Components for Parallelism, Distribution and Concurrency (IWJPDC'08), April 2008.
  [PDF] [BibTeX]
• On the Characterisation of Complex Transactional Memory Applications
  Mohammad Ansari, Christos Kotselidis, Kim Jarvis, Mikel Luján, Chris Kirkham and Ian Watson
  University of Manchester Technical Report CSPP-44, March 2008.
  [PDF] [BibTeX]
• Experiences using Adaptive Concurrency Control for Transactional Memory with Lee's Routing Algorithm
  Mohammad Ansari, Christos Kotselidis, Kim Jarvis, Mikel Luján, Chris Kirkham and Ian Watson
  In the 13th ACM SIGPLAN Symposium on Principles and Practice of Parallel Programming (PPoPP'08), February 2008.
  [PDF] [BibTeX] [Poster]
• Adaptive Concurrency Control for Transactional Memory
  Mohammad Ansari, Christos Kotselidis, Kim Jarvis, Mikel Luján, Chris Kirkham and Ian Watson
  In the 1st Workshop on Programmability Issues for Multi-Core Computers (MULTIPROG'08), January 2008.
  [PDF] [BibTeX]
• Designing a Distributed Software Transactional Memory System
  Christos Kotselidis, Mohammad Ansari, Kim Jarvis, Mikel Luján, Chris Kirkham and Ian Watson
  In the 3rd International Summer School on Advanced Computer Architecture and Compilation for Embedded Systems (ACACES'07), July 2007.
  [PDF] [BibTeX]
• Virtual Memory in the JAMAICA Chip Multiprocessor (Recommended MSc thesis)
  Mohammad Ansari
  University of Manchester, September 2005