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Re: timing of Table operation - a functional form


 
Further to Todd Gayley's reply to Jeff MacKie-Mason's enquiry

Timings with version 2.1 on a Mac IIfx

Needs["Statistics`ContinuousDistributions`"]

We start as before:

rdist = NormalDistribution[(1.1^(1/240)-1),(0.2/240)]

        NormalDistribution[0.000397205, 0.000833333]

Timing[ Short[ y = Table[Random[rdist],{240}] ] ]

       {3.73333 Second, {-0.000170285, -0.00148865, 0.000980608, <<236>>,

        0.000995661}}
        
But instead of 

Timing[ Product[(1+y[[i]]),{i,1,240}]-1 ]

       {0.583333 Second, 0.0949357}

use

Timing[ Times@@(1+y)-1 ]

       {0.35 Second, 0.0949357}
       
       
We can also write a ONE STEP FUNCTIONAL VERSION:

Timing[ 
       (Times@@(1+#)-1)&[Table[Random[rdist],{240}]] 
]
       
       {4. Second, 0.130792}

--- slightly quicker than the two step form.


Allan Hayes
Department of Mathematics
The University
Leicester LE1 7RH
U.K.
hay at leicester.ac.uk





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