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From "Martin Desruisseaux (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (SIS-384) (Affine → Passthrough → Affine) should be simplified as (Affine → Passthrough) or (Passthrough → Affine)
Date Sun, 07 Jan 2018 18:20:00 GMT

     [ https://issues.apache.org/jira/browse/SIS-384?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Martin Desruisseaux updated SIS-384:
------------------------------------
    Summary: (Affine → Passthrough → Affine) should be simplified as (Affine → Passthrough)
or (Passthrough → Affine)  (was: (Affine → Passthrough → Affine) should be simplified
as (Affine → Passthrough))

> (Affine → Passthrough → Affine) should be simplified as (Affine → Passthrough)
or (Passthrough → Affine)
> --------------------------------------------------------------------------------------------------------
>
>                 Key: SIS-384
>                 URL: https://issues.apache.org/jira/browse/SIS-384
>             Project: Spatial Information Systems
>          Issue Type: Improvement
>          Components: Referencing
>    Affects Versions: 0.5, 0.6, 0.7, 0.8
>            Reporter: Martin Desruisseaux
>            Priority: Minor
>              Labels: performance
>             Fix For: 1.0
>
>
> Below is an example of concatenated math transform. An "Affine" operation appears twice:
before and after the "Passthrough" operation:
> {noformat}
> Concat_MT[
>   Param_MT["Affine",
>     Parameter["num_row", 5],
>     Parameter["num_col", 5],
>     Parameter["elt_0_0", 0.025],
>     Parameter["elt_0_4", 3.0125],
>     Parameter["elt_1_1", -0.025],
>     Parameter["elt_1_4", 44.9875]],
>   PassThrough_MT[2, 1, Param_MT["Interpolation 1D",
>       Parameter["values", {2.0, 10.0, 20.0, 35.0, 50.0, 75.0, 100.0}]]],
>   Param_MT["Affine",
>     Parameter["num_row", 5],
>     Parameter["num_col", 5],
>     Parameter["elt_3_3", 3600000.0],
>     Parameter["elt_3_4", 1.5127128E12]]]
> {noformat}
> The last "Affine" operates only on passthrough coordinates. Consequently it could be
moved before the "Passthrouh" operation, which would allow concatenation with the first "Affine"
operation. It should not change the operation result, but can improve performance.
> This optimization is possible only for "Affine" that operate only on pass-through coordinates.
If the last "Affine" does not comply with this condition, maybe the first "Affine" does. So
we will need to test both.



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