From: | Bruno Wolff III <bruno(at)wolff(dot)to> |
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To: | Christopher Browne <cbbrowne(at)acm(dot)org> |
Cc: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: What about utility to calculate planner cost constants? |
Date: | 2005-03-22 15:17:07 |
Message-ID: | 20050322151707.GA5486@wolff.to |
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Thread: | |
Lists: | pgsql-performance |
On Tue, Mar 22, 2005 at 08:09:40 -0500,
Christopher Browne <cbbrowne(at)acm(dot)org> wrote:
>
> Are you certain it's a linear system? I'm not. If it was a matter of
> minimizing a linear expression subject to some set of linear
> equations, then we could model this as a Linear Program for which
> there are some perfectly good solvers available. (Few with BSD-style
> licenses, but we could probably get some insight out of running for a
> while with something that's there...)
For less than 100 equations and 100 unknowns, you should be able to use
naive solvers. After that you don't get very accurate answers without
being more careful. I still have my numerical analysis text books around
and can look algorithms up for doing this without too much trouble.
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