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MathGroup Archive 1998

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RE: Speeding up ReadList[]?



You can down load a copy of a package I wrote to read Excel files:
ftp://tea.fr.eu.org
The directory Mathematica/Spreadsheet contains a .m file and a .nb file
for documentation (in English).
Hope this helps,


**************************************** Jean-Marie THOMAS
Conseil et Audit en Inginierie de Calcul Strasbourg, France
****************************************

-----Original Message-----
From: John Sidles [mailto:sidles@u.washington.edu] To:
mathgroup@smc.vnet.net
Subject: [mg12028] [mg12020] Speeding up ReadList[]?


I use Mathematica to process Excel spreadsheets containing large arrays
({500,500}) of ASCII-coded floats.  To read in the lists, I use the
Mathematica function

      ReadList[stream, Number, RecordLists->True]

Everything works fine, except that as each new array, is read and
processed, ReadList[] gets slower and s l o w e r and
s...l...o...w...e...r.  The first ReadList[] takes only 40 seconds,
while the second ReadList[] can take 400 seconds or longer, and I don't
even know how long the third ReadList[] takes.

Each file is processed independently, and no large arrays are retained
in memory (they are stored as local variables inside Module[] blocks).
VIrtual memory is not used, and both the Kernel and the Notebook retain
plenty of unallocated memory.

Each file does generate a large Graphics[] object, but surprisingly,
Mathematica does not slow down while computing each graphic.  Thus,
ReadList[] is the only function evidencing a slowdown.

Neither the MathSource nor the FAQ seem to address this problem.  Has
anyone else run into this slowdown, and  how can it be avoided?

Thanks ... JAS





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