mirror of https://github.com/BOINC/boinc.git
45 lines
1.5 KiB
HTML
45 lines
1.5 KiB
HTML
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<title>Back end functions</title>
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<h2>Back end functions</h2>
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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
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by falsifying their CPU metrics or CPU times.
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The back end
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finds the minimum reported credit for the correct results of a given workunit,
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and assigns this amount of credit to all the correct results.
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This ensures that as long as a reasonable majority of participants
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don't falsify credit, almost all credit 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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