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Metaparallelism - Sensitivity to Probabilities

IP.com Disclosure Number: IPCOM000105834D
Original Publication Date: 1993-Sep-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 4 page(s) / 140K

Publishing Venue

IBM

Related People

Ekanadham, K: AUTHOR [+2]

Abstract

Metaparallelism is a process that determines the form of parallelism that is to be used in a specific application. Metaparallelism has two interfaces:

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Metaparallelism -  Sensitivity to Probabilities

      Metaparallelism is a process that determines the form of
parallelism that is to be used in a specific application.
Metaparallelism has two interfaces:

o   Information derived from prior executions.
o   Explicit statements made in the program or compiler output that
    bear on the form of parallelism.

Metaparallelism uses aspects of program behavior as it relates to the
capabilities of the Metaparallel Processor to cope with this behavior
to determine the type of parallelism that is to be pursued.
Metaparallelism employes speculation, that is, allocation of
resources to computations without a guarantee that these computations
are required, in order to complete the application in the faster
time.

The choice of parallelisms that metaparallelism can select from are:

o   Path-oriented forms of parallelism.
o   Path-oriented forms of parallelism with speculation.
o   Computation oriented parallelism with bifurcation at branches.
o   A set of independent paths that intercommunicate by sending
    messages to each other.
o   A combination of the above.

Metaparallelism employs means at its disposal to alter the form of
parallelism specified by the programmer/compiler at the source level
and to notify the programmer about significant aspects that interfere
with the parallelization of the application.

      The means of judging efficiency in non-deterministic situations
is to consider the probability measure associated with specific
outcomes.  The questions that relate to probabilities within
Metaparallelism include the sensitivity of the efficiency to specific
probabilities and to the manner in which the non-determinism is cast.
Within the deterministic behavior of programs, the needs of
parallelism and other expedients force relevant information to be
ignored and the action of the branch relative to a prediction
mechanism employed by the processor makes branch action appear
random.  The probability of error on a branch prediction depends on
the means employed to predict the branch and the actual pattern of
action of the branch.  Thus the identification of which branches are
important contributors to efficiency is not a simple matter.  The
processor can identify these branches based on the execution of the
program which incorporates the efficacy of the predictive techniques
used and the actual branch actions.  Thus branches that remain
intractable and affect the efficiency of the parallelization can be
identified.  Reporting on such branches and the degree to which they
affect efficiency can offer the programmer or an external agent an
opportunity to ameliorate the situation.

      Within Metaparallelism and SPECULATION, we have already
considered several issues that relate to decisions that can be cast
in terms of probabilities which determine:

o   The circumstances in which both paths following a branch should
    be executed.
o   The means of defi...