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[en] PIPELINE TRANSPORTATION PLANNERS / [pt] PLANEJADORES PARA TRANSPORTE EM POLIDUTOSFREDERICO DOS SANTOS LIPORACE 20 April 2006 (has links)
[pt] Oleodutos têm um papel importante no transporte de
petróleo e de seus derivados, pois são a maneira mais
eficaz de transportar grandes volumes por longas
distâncias. A motivação deste trabalho é que uma parte não
negligenciável do preço final de um derivado de petróleo é
influenciada pelo custo de transporte. Apesar disso, até
onde sabemos, apenas alguns autores trabalharam neste
problema específico, a maioria utilizando técnicas de
programação inteira. Este trabalho analisa a utilização de
técnicas de inteligência artificial, arcabouços de
software e simulação discreta orientada a eventos para a
construção de planejadores automáticos capazes de lidar
com instâncias reais de problemas de transporte em
oleodutos. A primeira contribuição dessa tese é a
especificação de um novo domínio para problemas de
planejamento, denominado PIPESWORLD. Este domínio é
inspirado no problema de transporte em oleodutos e
especificado em PDDL. Por sua estrutura original, ele foi
incorporado ao benchmark oficial da 4th International
Planner Competition, evento bi-anual que compara o
desempenho de diversos planejadores automáticos de
propósito geral. Mesmo sendo uma simplificação do problema
original, o PIPESWORLD se mostra um domínio bastante
desafiador para o estado da arte dos planejadores. É
demonstrado também que problemas de decisão derivados de
diversas configurações do Pipesworld são NP-Completos. A
segunda contribuição dessa tese é o arcabouço de software
PLANSIM. Este framework incorpora uma máquina de busca que
pode utilizar diversas estratégias, e define uma estrutura
que facilita a construção de planejadores automáticos
baseados em busca heurística direta que utilizam como
modelo do processo a ser planejado simuladores orientados
a eventos discretos. São apresentadas instanciações do
PLANSIM para a construção de planejadores para problemas
clássicos de como o das Torres de Hanoi e Blocksworld. A
terceira contribuição da tese é a instanciação do PLANSIM
para a construção de um planejador automático capaz de
tratar instâncias reais de planejamento de transporte em
oleodutos, denominado PLUMBER 05. A utilização de técnicas
de simulação discreta orientada a eventos para a
representação do modelo do sistema a ser planejado permite
que este seja bastante fiel ao problema original. Isto
somado ao uso do PLANSIM facilita a construção de
planejadores capazes de lidar com instâncias reais. / [en] Pipelines have an important role in oil and its
derivatives transportation,
since they are the most effective way to transport high
volumes through
long distances. The motivation for this work is that a non
negligible part
of the final price for those products are due to
transportation costs. Few
authors have addressed this problem, with most of the
previous work using
integer programming techniques. This work analyses the use
of Artificial
Intelligence techniques, discrete event simulators and
software frameworks
for building automated planners that are able to deal with
real-world oil
pipeline transportation instances. The first contribution
of this thesis is the
specification of a new planning domain called PIPESWORLD.
This domain
is inspired by the oil pipeline transportation problem,
and is defined
in PDDL. Due to its original structure, the PIPESWORLD
domain has
been incorporated to the 4th International Planning
Competition benchmark.
Even being a simplification of the original problem,
PIPESWORLD
instances in the benchmark are challenging to state of art
solvers. It is also
shown that decision problems based on PIPESWORLD
configurations are
NP-Hard. The second contribution of this thesis is the
PLANSIM opensource
framework. This framework incorporates a search engine
that may
use several different strategies, and defines a structure
that facilitates the
construction of automated planners based on heuristic
forward search that
use discrete event simulators as the model for the process
to be planned. The
third contribution of this thesis is a PLANSIM
instantiation that results in
an automated planner able to deal with real-world oil
pipeline transportation
instances, called PLUMBER 2. The use of discrete event
simulation
techniques for the model of the system to be planned
allows this model to
be very close to the original problem. This, in
conjunction with PLANSIM
usage, facilitates the construction of planners that are
able to cope with
real-world instances.
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Throughput Constrained and Area Optimized Dataflow Synthesis for FPGAsSun, Hua 21 February 2008 (has links) (PDF)
Although high-level synthesis has been researched for many years, synthesizing minimum hardware implementations under a throughput constraint for computationally intensive algorithms remains a challenge. In this thesis, three important techniques are studied carefully and applied in an integrated way to meet this challenging synthesis requirement. The first is pipeline scheduling, which generates a pipelined schedule that meets the throughput requirement. The second is module selection, which decides the most appropriate circuit module for each operation. The third is resource sharing, which reuses a circuit module by sharing it between multiple operations. This work shows that combining module selection and resource sharing while performing pipeline scheduling can significantly reduce the hardware area, by either using slower, more area-efficient circuit modules or by time-multiplexing faster, larger circuit modules, while meeting the throughput constraint. The results of this work show that the combined approach can generate on average 43% smaller hardware than possible when a single technique (resource sharing or module selection) is applied. There are four major contributions of this work. First, given a fixed throughput constraint, it explores all feasible frequency and data introduction interval design points that meet this throughput constraint. This enlarged pipelining design space exploration results in superior hardware architectures than previous pipeline synthesis work because of the larger sapce. Second, the module selection algorithm in this work considers different module architectures, as well as different pipelining options for each architecture. This not only addresses the unique architecture of most FPGA circuit modules, it also performs retiming at the high-level synthesis level. Third, this work proposes a novel approach that integrates the three inter-related synthesis techniques of pipeline scheduling, module selection and resource sharing. To the author's best knowledge, this is the first attempt to do this. The integrated approach is able to identify more efficient hardware implementations than when only one or two of the three techniques are applied. Fourth, this work proposes and implements several algorithms that explore the combined pipeline scheduling, module selection and resource sharing design space, and identifies the most efficient hardware architecture under the synthesis constraint. These algorithms explore the combined design space in different ways which represents the trade off between algorithm execution time and the size of the explored design space.
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