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Dynamic load balancing. Overview.


Dynamic load balancing. Overview. Simulation of combustion problems using multiprocessor computer systems For the – PowerPoint PPT presentation

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Title: Dynamic load balancing. Overview.

Dynamic load balancing.Overview.
  • Simulation of combustion problems using
    multiprocessor computer systems
  • For the "chemical part" of the problem the
    computational costs are very expensive and each
    point depends strongly on values of temperature
    and species concentration and can not be
    predetermined before calculation. In our case the
    calculation of chemical reactions requires more
    than 90 of total computational time. The reason
    of such fact is that in some of chemical
    processes the time of reactions is very small in
    comparison to gas dynamic time.
  • Many of the species exist and react only in the
    quite narrow region - in the flame front. The
    equal number of numerical points per processor
    does not imply the load balancing automatically
    therefore the special software was developed. The
    modified "processor farm" principles with master
    controlled data exchange between worker-nodes
    were used to achieve load balancing for chemical
    kinetic part.

The combustion zone
CH4 concentration
CO concentration
Dynamic load balancing. Problem statement.
  • The system of equations, governing gas-dynamic
    and chemical kinetic processes under combustion,
  • expressed in operator form is the following
  • Here A is a nonlinear operator, ? - density,
  • y(i) - mass fraction of the i-th species,
  • u, v - components of velocity along x and y
  • p - pressure, E - total energy,
  • ?I - mass velocity of formation of substance in
    all responses.
  • I. Gasdynamic block (GD)
  • GD block is approximated via half-implicit
    finite-difference scheme

Dynamic load balancing.Goals.
  • The main goal was to develop a library for
    dynamic load balancing of loosely coupled
    distributed tasks when using a heterogeneous
    multiprocessor systems
  • Independent tasks are assigned to the nodes of
    the mesh, which is distributed over processors
    according to the domain decomposition method

When a task is processed, the result should be
returned to the corresponding processor
regardless where it was obtained
Dynamic load balancing.Issues.
  • Algorithm is based on collective farm, but is
    devoid of its
  • shortcoming. It is achieved due to a great
    reduction of traffic as each processing node
    possesses equal controlling features.Two (or
    more) processes are executed on each node -
    communication (control) process and operating
    process (or processes).
  • Algorithm for load balancing is based on the
    following principles
  • each processor primarily operates its local
    points (that are
  • stored in its memory)
  • the processor can request points from the others
    provided that
  • a) all local points are calculated or
    transferred for handling to other processors
  • b) transmission of points for handling to
    otherprocessors and handling of local pointsare
    fulfilled simultaneously.

Dynamic load balancing. Status.
  • The dynamic load balancing library was developed.
    The library allows to efficiently schedule the
    stream of tasks, which are distributed according
    to the domain decomposition method.
  • The library provides efficient use of
    metacomputers. The mesh may be stored within one
    or both clusters
  • An approach is offered to the integration of
    more than two clusters forsolving combustion

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