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AbsoluteTime[] runs slowly?
*To*: mathgroup at smc.vnet.net
*Subject*: [mg122286] AbsoluteTime[] runs slowly?
*From*: Robert McHugh <bob_mchugh_2000 at yahoo.com>
*Date*: Sun, 23 Oct 2011 06:25:28 -0400 (EDT)
*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com
*Reply-to*: Robert McHugh <bob_mchugh_2000 at yahoo.com>
The following code takes over a minute to run on my machine. Is this expected behavior?
t = {"14-May-10 09:58:05", {"Day", "-", "MonthNameShort", "-", "YearShort", " ", "Hour", ":", "Minute", ":", "Second"}};
tList = Table[t, {i, 100000}];
a = Timing[AbsoluteTime[#] & /@ tList ;]
For reference, an operation like the following takes less than a tenth of a second. (Of course this second example needs quite a bit of modification to provide a correct answer, but it does show how fast the program can operate on a large list.)
t = {14, 5, 10, 9, 58, 05};
tList = Table[t, {i, 100000}];
a = Timing[( ((#[[3]] 0 + #[[2]] 30 + #[[1]]24) + #[[4]]) 60 + #[[5]]) 60 + #[[6]] & /@ tList;]
Some background: am analyzing some historical data (about 500 000 records, one data point a minute for about a year) and am making a few utilities to retrieve the data for any given time interval. My original plan was to change the time stamp to absolute time and then use a select statement. This step in the above example, changing the time stamps to absolute time, is the rate limiting step in the code (everything else runs in about 5 seconds).
Was wondering if someone could explain why AbsoluteTime[] is relatively slow operation and perhaps some faster operations for date and time comparisons.
Thanks
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