IO-Performance of Mathematica 4.1
- To: mathgroup at smc.vnet.net
- Subject: [mg44659] IO-Performance of Mathematica 4.1
- From: Marko Kastens <Kastens at Hamburg.baw.de>
- Date: Thu, 20 Nov 2003 03:16:25 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
Hi!
I'am searching for a good (fast) way to import big datasets in Mathematica 4.1.
What I've done so far:
- The read-in from the _orignal_ (ASCII)file needs 97 sec. (a 5xxxx x 2
matrix)
- Exporting my matrix using Export[] with "List" or "Table" needs
(nearly) infinity of time :-(
- Exporting the matrix with the HDF (Hierarchy Data Format): 7 seconds
:-) Great, but...
- Importing the matrix with HDF: fast but wrong: the HDF seems to
supports only Real64. My first column is a 10-digit-Integer representing
the MM-time-format. By converting this to yyExx the last digits get lost
and my time is doing funny jumps...
- using the Experimental-Functions like this:
<< Experimental`
t0 = AbsoluteTime[];
strm = OpenWrite["tmp0.bin", DOSTextFormat -> False];
BinaryExport[strm, Length[data], "Integer32"]
For[i = 1, i < Length[data] + 1,
{
BinaryExport[strm, data[[i]], {"Integer64", "Real64", "Integer64"}]
}; i++]
Close[strm];
Print[AbsoluteTime[] - t0];
it takes 415 seconds to export and 247 seconds to import. Even worser
than importing the original.
Only the good old ASCII-way is better:
t0 = AbsoluteTime[];
strm = OpenWrite["tmp1.dat"];
Write[strm, Length[data]]
For[i = 1, i < Length[data] + 1,
{
Write[strm, data[[i, 1]]],
Write[strm, data[[i, 2]]],
Write[strm, data[[i, 3]]]
}; i++]
Close[strm];
Print[AbsoluteTime[] - t0];
It takes 32 seconds to export and 16 seconds to import.
Hmm, normaly binary-import/export is faster than ascii-import/export.
Does anybody know a proper and fast method? Thanks a lot.
marko