boinc/doc/credit.html

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<title>Computation credit</title>
<body bgcolor=ffffff>
<h2>Computation credit</h2>
<p>
Each project gives you <b>credit</b> for the computations your
computers performs for the project.
These credits are used to generate web-site "leaderboards" showing
individuals, teams, and categories (countries, CPU types, etc.)
ranked by credit.
<p>
BOINC's credit system is based on a "reference computer" that does
<ul>
<li>1 billion floating-point multiply/adds per second
<li>1 billion integer multiply/adds per second
<li>4 billion bytes per second of traffic to and from main memory
(sequential, half reads and half writes)
</ul>
BOINC's unit of credit, the <b>Cobblestone</b>,
is one day of CPU time on the reference computer.
(Credit should ideally reflect network transfer and disk storage as well
as computation.
But it's hard to verify these activities,
so for now they aren't included.)
<p>
Each project maintains two types of credit:
<ul>
<li> <b>Total credit</b>:
The total number of Cobblestones performed.
<li> <b>Recent average credit</b>:
The average number of Cobblestones per day performed recently.
This average decreases by a factor of two every week.
</ul>
<p>
Both types of credit (total and recent average)
are maintained for each user and host.