Commit dd0f4578 authored by Pedro Gonnet's avatar Pedro Gonnet
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added a brief description of how the space is decomposed.

parent 85c3e1ff
......@@ -347,7 +347,8 @@ techniques easier, we chose to implement our own task scheduler
in \swift, which has since been back-ported as the general-purpose
\qs task scheduler \cite{gonnet2013quicksched}.
This also allowed us to extend the scheduler with the concept of
task conflicts.
task conflicts and integrate the asynchronous communication
scheme described below.
Despite its advantages, and the variety of implementations,
task-based parallelism is rarely used in
......@@ -360,9 +361,19 @@ which is usually not an option for large and complex codebases.
Since we were re-implementing \swift from scratch, this was not an issue.
The tree-based neighbour-finding described above was replaced with a more
task-friendly approach as described in \cite{ref:Gonnet2015}.
task-friendly approach as described in \cite{ref:Gonnet2015}, in which
the domain is first decomposed into a grid of {\em cells} of edge length
larger or equal to the largest particle radius.
An initial set of interaction tasks is then defined over all neighbouring
pairs of cells such that if two particles are close enough to interact,
they are either in the same cell or they span a pair of neighbouring cells.
These initial interaction tasks are then refined by recursively
splitting cells that contain more than a certain number of particles
and replacing tasks that span a pair of split cells with tasks
spanning the neighboring sub-cells.
Particle interactions are computed within, and between pairs, of
hierarchical {\em cells} containing one or more particles.
hierarchical cells containing one or more particles.
The dependencies between the tasks are set following
equations \eqn{rho}, \eqn{dvdt}, and \eqn{dudt}, i.e.~such that for any cell,
all the tasks computing the particle densities therein must have
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