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|Title: ||Contraint solving on massively parallel systems|
|Authors: ||Roque, Pedro Miguel da Silva|
|Advisors: ||Abreu, Salvador Luís de Bethencourt Pinto de|
Pedro, Vasco Fernando de Figueiredo Tavares
|Keywords: ||Constraint solving|
|Issue Date: ||3-Jul-2020|
|Publisher: ||Universidade de Évora|
Applying parallelism to constraint solving seems a promising approach and it has been done with varying
degrees of success. Early attempts to parallelize constraint propagation, which constitutes the core of
traditional interleaved propagation and search constraint solving, were hindered by its essentially sequential
nature. Recently, parallelization efforts have focussed mainly on the search part of constraint solving. A
particular source of parallelism has become pervasive, in the guise of GPUs, able to run thousands of parallel
threads, and they have naturally drawn the attention of researchers in parallel constraint solving.
This thesis addresses the challenges faced when using multiple devices for constraint solving, especially
GPUs, such as deciding on the appropriate level of parallelism to employ, load balancing and inter-device
communication. To overcome these challenges new techniques were implemented in a new constraint
solver, named Parallel Heterogeneous Architecture Constraint Toolkit (PHACT), which allows to use one
or more CPUs, GPUs, Intel Many Integrated Cores (MIC) and any other device compatible with OpenCL
to solve a constraint problem.
Several tests were made to measure the capabilities of some GPUs to solve constraint problems, and
the conclusions of these tests are described in this thesis. PHACT’s architecture is presented and its
performance was measured in each one of five machines, comprising eleven CPUs, six GPUs and two MICs.
The tests were made using 10 constraint satisfaction problems, consisting in counting all the solutions,
finding one solution or optimizing. Each of the problems has been instantiated with up to three different
dimensions. PHACT’s performance was also compared with the ones of Gecode, Choco and OR-Tools.
In the end, these tests allowed to detect which techniques implemented in PHACT were already achieving
the expected results, and to point changes that may improve PHACT’s performance.|
|Appears in Collections:||BIB - Formação Avançada - Teses de Doutoramento|
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