mirror of https://github.com/BOINC/boinc.git
75 lines
2.5 KiB
PHP
75 lines
2.5 KiB
PHP
<?php
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require_once("docutil.php");
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page_head("Work distribution");
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echo "
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A host asks a project for work by including a
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".html_text("<work_req_seconds>X</work_req_seconds>")."
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element in a scheduler RPC request message.
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This asks the scheduler to return enough work to
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keep all the host's processors busy for X seconds,
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given the host's typical usage
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(i.e. the fraction of time it's turned off
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or BOINC is suspended, and the other processes that it executes).
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<p>
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BOINC's work distribution policy addresses the
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(sometimes conflicting) goals of keeping hosts as busy as possible,
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while minimizing the impact of
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<ul>
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<li> Hosts that repeatedly return results with error outcomes,
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due to a host-specific problem.
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<li> Malicious participants who attempt to obtain multiple
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results of the same workunit,
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in an attempt to obtain unearned credit
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or have erroneous results accepted as correct.
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</ul>
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Work distribution is constrained by a number of rules:
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<ul>
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<li> A result is sent only if an application version
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is available for the host's platform.
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<li>
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A result is not sent if its disk or memory requirements
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are not met by the host.
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<li>
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A result is not sent if the estimated latency
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(based on the host's CPU speed and usage parameters)
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exceeds the workunit's latency bound.
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<li>
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A result is not sent if the project has specified a
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<a href=configuration.php>one result per user per workunit</a>
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flag, and a result of the same workunit has already been
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sent to a host belonging to the same user.
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<li>
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A result is not sent if the project has specified a
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<a href=configuration.php>daily result quota</a> per host,
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and the host has already been sent that many results.
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<li>
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A project can specify a limit on the
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<a href=configuration.php>number of results sent per RPC</a>.
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<li>
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A result is not sent if
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<a href=homogeneous_redundancy.php>homogeneous redundancy</a>
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is enabled and another result of the same workunit
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has been sent to a different type of host.
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<li>
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No results are sent of the core client has a different
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major version than the scheduling server.
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</ul>
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In general, the BOINC scheduler responds to a work request
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by enumerating unsent results from the database,
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filtering them by the above criteria,
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sending them to the host,
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and continuing until requested duration X is reached.
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<p>
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For projects that have very large input files,
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each of which is used by many workunit,
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BOINC offers an alternative work distribution policy
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called <a href=sched_locality.php>locality scheduling</a>.
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";
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page_tail();
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?>
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