Commit db66234a authored by arpad rimmel's avatar arpad rimmel

new team seminar

parent 2e18b754
Title: Programming computing media
date: 2020-03-20 14:30
slug: 2020-03-20-team-seminar
Authors: Frédéric Gruau
institution: LRI
tags: Team seminar, combinatorics
location: LRI, 445
summary: We consider computing media consisting of billions of small identical
Processing Elements (PE) communicating locally in space, and with an
homogeneous and isotropic distribution.
Computing media can scale arbitrary in size. Thus, they represent
parallel architectures whose power can grow without limit. However,
programming computing media is difficult.
In general, mapping a particular algorithm on a parallel architecture is
not an easy task. In the case of computing media, the difficulty is much
higher, due to the simplicity of each PEs, and the locality of the
connections between PEs. The spatial location of PEs must be taken into
account, because information propagates from one PE to the next nearby PEs.
What is feasible though, is to simulate physical laws. This is due to
the isotropic and uniform distribution of PEs in space. Our road-map is
to simulate an "empowering" artificial physics in 2D-space, that will
implement a virtual machine facilitating programming.
This artificial physics simulates simplified membrane-agents, dividing
and constantly homogenizing by exerting repulsive forces between each
other. Two adjacent membranes can also be connected, in which case an
attractive force maintain them nearby. The dynamic unfolding of the
membrane-network resembles the biological cellular developmental process
whereby an initial ancestor cell develops repeatedly.
The development is driven by a flow of instructions sent by an outside
host, through the border of the computing medium. Those instructions
determine when and where division occurs, and how membranes get
connected to each other, so as to match the need of generic families of
parallel algorithms:
1- For systolic algorithms based on nested loops operating on arrays,
the network developed must be a regular systolic grid;
2- For the divide-and-conquer algorithms, it must be a set of
encapsulated membranes representing the dynamic tree of
divide-and-conquer calls.
During this talk, we will present the rule implementing membranes, and
increasingly complex examples of developments. In particular we will
show the development of the regular grid.
The behavior is mathematically correct when the network of PEs in the
computing medium is a maximal planar graph. For the moment, though, we
have simulation running only for Hexagonal Cellular Automata (CA) which
are easier and quicker to simulate than the general case. The resulting
rule is quite complex: 77 bits of state and 13878 gates per PEs, up to
now. This implied the development of a compiler of CA-rules to reach an
acceptable simulation speed.
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