mirror of https://github.com/BOINC/boinc.git
50 lines
1.6 KiB
PHP
50 lines
1.6 KiB
PHP
<?
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require_once("docutil.php");
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page_head("Back end functions");
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echo "
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<p>
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The general functions of a project back end include:
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<ul>
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<li> <b>Generate work</b>.
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<p>
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<li> <b>Reissue results</b>.
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Hosts may fail to return results for various reasons;
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such results are 'lost'.
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Lost and erroneous results may prevent
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finding a canonical result for a workunit.
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The 'result reissue' mechanism generates additional
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results as needed to find a canonical result.
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<p>
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<li> <b>Select canonical results</b>.
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Communication from the core client can easily be altered or forged.
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Output files may be wrong.
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This can result from tampering or hardware failures.
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This problem can be addressed
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by <b>redundant computing</b>
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In this approach, each workunit is processed at least twice.
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The project back end waits until a minimum number of results have been returned,then compares the results and decides which are considered correct.
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The notion of equality of results,
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and the policy for deciding which are correct, are project-specific.
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<p>
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<li> <b>Grant credit</b>.
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Some users will attempt to get undeserved credit by falsifying their CPU
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metrics or CPU times. Each project and application can have its own
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credit-granting algorithm, for example granting the minimum or the mean of
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the median of all claimed credits (during validation time). The granted
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credit is assigned to all correct results. This ensures that as long as a
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reasonable majority of participants don't falsify credit, almost all credit
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accounting will be correct.
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<p>
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<li> <b>Assimilate results</b>.
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<p>
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<li> <b>Delete files</b>.
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<p>
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<li> <b>Detect 'problem' workunits</b>.
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</ul>
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";
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page_tail();
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?>
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