5,911 research outputs found
Two novel evolutionary formulations of the graph coloring problem
We introduce two novel evolutionary formulations of the problem of coloring
the nodes of a graph. The first formulation is based on the relationship that
exists between a graph's chromatic number and its acyclic orientations. It
views such orientations as individuals and evolves them with the aid of
evolutionary operators that are very heavily based on the structure of the
graph and its acyclic orientations. The second formulation, unlike the first
one, does not tackle one graph at a time, but rather aims at evolving a
`program' to color all graphs belonging to a class whose members all have the
same number of nodes and other common attributes. The heuristics that result
from these formulations have been tested on some of the Second DIMACS
Implementation Challenge benchmark graphs, and have been found to be
competitive when compared to the several other heuristics that have also been
tested on those graphs.Comment: To appear in Journal of Combinatorial Optimizatio
Modeling the input history of programs for improved instruction-memory performance
When a program is loaded into memory for execution, the relative position of
its basic blocks is crucial, since loading basic blocks that are unlikely to be
executed first places them high in the instruction-memory hierarchy only to be
dislodged as the execution goes on. In this paper we study the use of Bayesian
networks as models of the input history of a program. The main point is the
creation of a probabilistic model that persists as the program is run on
different inputs and at each new input refines its own parameters in order to
reflect the program's input history more accurately. As the model is thus
tuned, it causes basic blocks to be reordered so that, upon arrival of the next
input for execution, loading the basic blocks into memory automatically takes
into account the input history of the program. We report on extensive
experiments, whose results demonstrate the efficacy of the overall approach in
progressively lowering the execution times of a program on identical inputs
placed randomly in a sequence of varied inputs. We provide results on selected
SPEC CINT2000 programs and also evaluate our approach as compared to the gcc
level-3 optimization and to Pettis-Hansen reordering
Alstroemeriaceae na região Sul do Brasil.
Resumo: Alstroemeriaceae compreende ervas perenes eretas ou volúveis, rizomatosas de folhas geralmente ressupinadas. É encontrada em quase todos os tipos de hábitats, de florestas a brejos e até desertos. A família está representada na Região Sul do Brasil pelo gênero Alstroemeria L., incluindo 9 espécies: Alstroemeria albescens M.C.Assis, A. amabilis M.C.Assis, A. apertiflora Baker, A. cunha Vell., A. inodora Herb., A. isabelleana Herb., A. malmeana Kraenzl., A. psittacina Lehm., A. sellowiana Seub. ex Schenk, e pelo gênero Bomarea Mirb. incluindo apenas a espécie B. edulis (Tussac) Herb. Neste trabalho são apresentadas nova sinonimização, chaves de identificação, descrição das espécies, ilustrações e comentários. Palavras-chave: Alstroemeria, Bomarea, flora, sistemática, Brasil Abstract: Alstroemeriaceae comprises perennial herbs that are erect or twining and rhizomatous. The leaves are generally resupinate. They are found in a wide range of habitats including cloud forests, swamps and desert areas. The family is represented at South of Brazil by 2 genus: Alstroemeria L. and Bomarea Mirb. Alstroemeria included 9 species: Alstroemeria albescens M.C.Assis, A. amabilis M.C.Assis, A. apertiflora Baker, A. cunha Vell., A. inodora Herb., A. isabelleana Herb., A. malmeana Kraenzl., A. psittacina Lehm., A. sellowiana Seub. ex Schenk. Bomarea included just one specie, B. edulis (Tussac) Herb. New synonym, key to genera and species, descriptions, illustrations and comments are presented
New species of Alstroemeria altroemeriaceae from the Brazilian Savannas.
Two new species of Alstroemeria (Alstroemeriaceae) from the Brazilian savannas are described: A. stenophylla M. C. Assis, which is characterized by its narrow linear-lanceolate leaves, concentrated on the distal region of the vegetative stem, and for its ruby-spotted inner tepals, close to A. gardneri Baker and A. plantaginea Martiuse x Schultes & Schultesf .; and A . tombolatoana M. C. Assis, which may be recognized by its coriaceous leaves, outer tepals oblong-spatulate, without patterning, but the inner tepals spatulate and ruby-maculates, sympatric with A. gardneri. Descriptions, comments, and illustrations are presented
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