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Top Forums UNIX for Advanced & Expert Users Help optimizing sort of large files Post 302925065 by achenle on Thursday 13th of November 2014 05:59:06 PM
Old 11-13-2014
Generally it's possible to beat default page-cached IO by 10-20% - but only if you can accurately predict your access pattern. And if you screw up and the data isn't accessed in the pattern you thought it would be, you can really destroy performance, especially on RAID5/6 disk systems.

Basically, the default IO is pretty darn good almost all the time. Don't try to beat it unless you really have to - for example, a $600 million system where there's more data to process then you ever could and the amount you process is limited by your IO speed.
 

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LinPred(3)						User Contributed Perl Documentation						LinPred(3)

NAME
PDL::Filter::LinPred - Linear predictive filtering SYNOPSIS
$a = new PDL::Filter::LinPred( {NLags => 10, LagInterval => 2, LagsBehind => 2, Data => $dat}); ($pd,$corrslic) = $a->predict($dat); DESCRIPTION
A filter by doing linear prediction: tries to predict the next value in a data stream as accurately as possible. The filtered data is the predicted value. The parameters are NLags Number of time lags used for prediction LagInterval How many points each lag should be LagsBehind If, for some strange reason, you wish to predict not the next but the one after that (i.e. usually f(t) is predicted from f(t-1) and f(t-2) etc., but with LagsBehind => 2, f(t) is predicted from f(t-2) and f(t-3)). Data The input data, which may contain other dimensions past the first (time). The extraneous dimensions are assumed to represent epochs so the data is just concatenated. AutoCovar As an alternative to Data, you can just give the temporal autocorrelation function. Smooth Don't do prediction or filtering but smoothing. The method predict gives a prediction for some data plus a corresponding slice of the data, if evaluated in list context. This slice is given so that you may, if you wish, easily plot them atop each other. The rest of the documentation is under lazy evaluation. AUTHOR
Copyright (C) Tuomas J. Lukka 1997. All rights reserved. There is no warranty. You are allowed to redistribute this software / documenta- tion under certain conditions. For details, see the file COPYING in the PDL distribution. If this file is separated from the PDL distribu- tion, the copyright notice should be included in the file. perl v5.8.0 2000-05-23 LinPred(3)
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