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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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