taskGNU Astronomy Utilities - Tasks: task #16066, Match program should avoid...

 
 

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task #16066: Match program should avoid permutations

Submitter:  Mohammad Akhlaghi <makhlaghi>
Submitted:  Mon 01 Nov 2021 11:17:10 PM UTC
   
 
Should Start On:  Mon 01 Nov 2021 12:00:00 AM UTC Should be Finished on:  Mon 01 Nov 2021 12:00:00 AM UTC
Category:  Match Priority:  5 - Normal
Item Group:  Enhancement Status:  Done
Privacy:  Public Assigned to:  makhlaghi
Percent Complete:  100% Open/Closed:  Closed
Effort:  0.00

Mon 15 Nov 2021 02:11:40 AM UTC, comment #1: 

This task was completed in Commit 095c7888b225e.

Mohammad Akhlaghi <makhlaghi>
Group administrator
Mon 01 Nov 2021 11:17:10 PM UTC, original submission:  

Currently the Match program takes the fully input permutation, applies it over the full length of both inputs (even the non-matched rows), then only selects the top rows (this is how the permutation is defined).

However, when the inputs are large (for example 1 million rows), and only a small fraction match (for example 30000 rows), the permutation above will actually be slower than the actual matching!

So instead of permuting the whole array, its simpler to just allocate the output columns separately and fill them with the order specified in the permutation (only for the rows that matched).

This won't have any effect for a small input, but for a large input in the scenario above, it will lead to major speed improvements.

Mohammad Akhlaghi <makhlaghi>
Group administrator

 

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    Follow 4 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2021-11-15 makhlaghi StatusNone Done
        Percent Complete0% 100%
        Assigned toNone makhlaghi
        Open/ClosedOpen Closed

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