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Team Show image information

Team

Dr. Hassan Ghasemzadeh Mohammadi

Contact
Dr. Hassan Ghasemzadeh Mohammadi

Computer Engineering

Postdoc

Phone:
+49 5251 60-4344
Fax:
+49 5251 60-4250
Office:
O3.134
Office hours:

by appointment

Web:
Web(external):
Visitor:
Pohlweg 51
33098 Paderborn

Lectures

2017

  • Lecture: Algorithms for Synthesis and Optimization of Integrated Circuits, Master, Paderborn University

Projects

  • [Link to projects]

Publications


Open list in Research Information System

Conferences

Jump Search: A Fast Technique for the Synthesis of Approximate Circuits

L.M. Witschen, H. Ghasemzadeh Mohammadi, M. Artmann, M. Platzner, in: Proceedings of the 2019 on Great Lakes Symposium on VLSI - GLSVLSI '19, ACM, 2019

State-of-the-art frameworks for generating approximate circuits automatically explore the search space in an iterative process - often greedily. Synthesis and verification processes are invoked in each iteration to evaluate the found solutions and to guide the search algorithm. As a result, a large number of approximate circuits is subjected to analysis - leading to long runtimes - but only a few approximate circuits might form an acceptable solution. In this paper, we present our Jump Search (JS) method which seeks to reduce the runtime of an approximation process by reducing the number of expensive synthesis and verification steps. To reduce the runtime, JS computes impact factors for each approximation candidate in the circuit to create a selection of approximate circuits without invoking synthesis or verification processes. We denote the selection as path from which JS determines the final solution. In our experimental results, JS achieved speed-ups of up to 57x while area savings remain comparable to the reference search method, Simulated Annealing.

@inproceedings{Witschen_Ghasemzadeh Mohammadi_Artmann_Platzner_2019, place={New York, NY, USA}, title={Jump Search: A Fast Technique for the Synthesis of Approximate Circuits}, DOI={10.1145/3299874.3317998}, booktitle={Proceedings of the 2019 on Great Lakes Symposium on VLSI  - GLSVLSI ’19}, publisher={ACM}, author={Witschen, Linus Matthias and Ghasemzadeh Mohammadi, Hassan and Artmann, Matthias and Platzner, Marco}, year={2019} }


An MCTS-based Framework for Synthesis of Approximate Circuits

M. Awais, H. Ghasemzadeh Mohammadi, M. Platzner, in: 26th IFIP/IEEE International Conference on Very Large Scale Integration (VLSI-SoC), 2018, pp. 219-224

Approximate computing has become a very popular design strategy that exploits error resilient computations to achieve higher performance and energy efficiency. Automated synthesis of approximate circuits is performed via functional approximation, in which various parts of the target circuit are extensively examined with a library of approximate components/transformations to trade off the functional accuracy and computational budget (i.e., power). However, as the number of possible approximate transformations increases, traditional search techniques suffer from a combinatorial explosion due to the large branching factor. In this work, we present a comprehensive framework for automated synthesis of approximate circuits from either structural or behavioral descriptions. We adapt the Monte Carlo Tree Search (MCTS), as a stochastic search technique, to deal with the large design space exploration, which enables a broader range of potential possible approximations through lightweight random simulations. The proposed framework is able to recognize the design Pareto set even with low computational budgets. Experimental results highlight the capabilities of the proposed synthesis framework by resulting in up to 61.69% energy saving while maintaining the predefined quality constraints.

@inproceedings{Awais_Ghasemzadeh Mohammadi_Platzner_2018, title={An MCTS-based Framework for Synthesis of Approximate Circuits}, booktitle={26th IFIP/IEEE International Conference on Very Large Scale Integration (VLSI-SoC)}, author={Awais, Muhammad and Ghasemzadeh Mohammadi, Hassan and Platzner, Marco}, year={2018}, pages={219–224} }


Journal Articles

CIRCA: Towards a Modular and Extensible Framework for Approximate Circuit Generation

L.M. Witschen, T. Wiersema, H. Ghasemzadeh Mohammadi, M. Awais, M. Platzner, Microelectronics Reliability (2019), 99, pp. 277-290

Existing approaches and tools for the generation of approximate circuits often lack generality and are restricted to certain circuit types, approximation techniques, and quality assurance methods. Moreover, only few tools are publicly available. This hinders the development and evaluation of new techniques for approximating circuits and their comparison to previous approaches. In this paper, we first analyze and classify related approaches and then present CIRCA, our flexible framework for search-based approximate circuit generation. CIRCA is developed with a focus on modularity and extensibility. We present the architecture of CIRCA with its clear separation into stages and functional blocks, report on the current prototype, and show initial experiments.

@article{Witschen_Wiersema_Ghasemzadeh Mohammadi_Awais_Platzner_2019, title={CIRCA: Towards a Modular and Extensible Framework for Approximate Circuit Generation}, volume={99}, DOI={10.1016/j.microrel.2019.04.003}, journal={Microelectronics Reliability}, publisher={Elsevier}, author={Witschen, Linus Matthias and Wiersema, Tobias and Ghasemzadeh Mohammadi, Hassan and Awais, Muhammad and Platzner, Marco}, year={2019}, pages={277–290} }


Preprint

CIRCA: Towards a Modular and Extensible Framework for Approximate Circuit Generation

L.M. Witschen, T. Wiersema, H. Ghasemzadeh Mohammadi, M. Awais, M. Platzner, in: Third Workshop on Approximate Computing (AxC 2018), 2018

Existing approaches and tools for the generation of approximate circuits often lack generality and are restricted to certain circuit types, approximation techniques, and quality assurance methods. Moreover, only few tools are publicly available. This hinders the development and evaluation of new techniques for approximating circuits and their comparison to previous approaches. In this paper, we first analyze and classify related approaches and then present CIRCA, our flexible framework for search-based approximate circuit generation. CIRCA is developed with a focus on modularity and extensibility. We present the architecture of CIRCA with its clear separation into stages and functional blocks, report on the current prototype, and show initial experiments.

@article{Witschen_Wiersema_Ghasemzadeh Mohammadi_Awais_Platzner, title={CIRCA: Towards a Modular and Extensible Framework for Approximate Circuit Generation}, journal={Third Workshop on Approximate Computing (AxC 2018)}, author={Witschen, Linus Matthias and Wiersema, Tobias and Ghasemzadeh Mohammadi, Hassan and Awais, Muhammad and Platzner, Marco} }


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