Speeding up ReadList[]?
- To: mathgroup@smc.vnet.net
- Subject: [mg12020] Speeding up ReadList[]?
- From: sidles@u.washington.edu (John Sidles)
- Date: Fri, 17 Apr 1998 03:40:55 -0400
- Organization: University of Washington, Seattle
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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