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Restrict size 1 limitation to source field in regridding#249

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davidhassell merged 10 commits intoNCAS-CMS:masterfrom
ThibHlln:support-one-element-grid
Sep 30, 2021
Merged

Restrict size 1 limitation to source field in regridding#249
davidhassell merged 10 commits intoNCAS-CMS:masterfrom
ThibHlln:support-one-element-grid

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@ThibHlln ThibHlln commented Aug 24, 2021 •
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resolves #250

Hi David, Hi Sadie,

With the simple change contained in this PR, the code below would work, which is not currently the case (i.e. a regridding towards a single grid cell domain).

import cf
import numpy

# source field (2x3 grid)
fld1 = cf.Field()
fld1.set_construct(
    cf.DimensionCoordinate(
        properties={'standard_name': 'longitude',
                    'units': 'degrees_east',
                    'axis': 'X'},
        data=cf.Data([5, 15, 25]),
        bounds=cf.Bounds(data=cf.Data([[0, 10], [10, 20], [20, 30]]))
    ),
    axes=fld1.set_construct(cf.DomainAxis(size=3))
)
fld1.set_construct(
    cf.DimensionCoordinate(
        properties={'standard_name': 'latitude',
                    'units': 'degrees_north',
                    'axis': 'Y'},
        data=cf.Data([55, 65]),
        bounds=cf.Bounds(data=cf.Data([[50, 60], [60, 70]]))
    ),
    axes=fld1.set_construct(cf.DomainAxis(size=2))
)

# destination field (1x1 grid)
fld2 = cf.Field()
fld2.set_construct(
    cf.DimensionCoordinate(
        properties={'standard_name': 'longitude',
                    'units': 'degrees_east',
                    'axis': 'X'},
        data=cf.Data([15]),
        bounds=cf.Bounds(data=cf.Data([[0, 30]]))
    ),
    axes=fld2.set_construct(cf.DomainAxis(size=1))
)
fld2.set_construct(
    cf.DimensionCoordinate(
        properties={'standard_name': 'latitude',
                    'units': 'degrees_north',
                    'axis': 'Y'},
        data=cf.Data([60]),
        bounds=cf.Bounds(data=cf.Data([[50, 70]]))
    ),
    axes=fld2.set_construct(cf.DomainAxis(size=1))
)

# set some data
fld1.set_data(numpy.arange(6).reshape(2, 3), axes=('Y', 'X'))
fld2.set_data(numpy.ones((1, 1)), axes=('Y', 'X'))

# test regridding on all existing methods
for m in ['linear', 'conservative', 'conservative_2nd', 
          'patch', 'nearest_stod', 'nearest_dtos']:
    
    fld3 = fld1.regrids(fld2, method=m)
    
    print(fld3.data)

@ThibHlln ThibHlln changed the title restrict size 1 limitation to source grid restrict size 1 limitation to source grid in regridding Aug 24, 2021
@ThibHlln ThibHlln changed the title restrict size 1 limitation to source grid in regridding restrict size 1 limitation to source field in regridding Aug 24, 2021
@ThibHlln ThibHlln changed the title restrict size 1 limitation to source field in regridding Restrict size 1 limitation to source field in regridding Aug 24, 2021
@davidhassell
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davidhassell commented Aug 25, 2021

Hi Thibault,

Would you mind copying the above into an issue and referencing that issue from this PR? (https://ncas-cms.github.io/cf-python/contributing.html#preparing-pull-requests) - I'll reply over there ...

Thanks, David

@davidhassell davidhassell mentioned this pull request Aug 25, 2021
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davidhassell reviewed Aug 25, 2021
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@ThibHlln
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ThibHlln commented Aug 27, 2021

Hi David,

As discussed in #250, it seems that the source grid can be with size 1 dimensions for some of the methods.

My latest commit reflects that and also un-indent the check in regrid_get_latlon to cover both coords_2D = False and coords_2D = True. However, for it to work, I also needed to remove the squeeze on src_data in regrids, I am not sure whether this is a problem?

The testing script below should work now (same fields as above):

for m in ['conservative_1st', 'conservative_2nd', 'nearest_stod', 'nearest_dtos']:
    fld3 = fld2.regrids(fld1, method=m)
    print(fld3.array)

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davidhassell commented Sep 28, 2021

Hi @ThibHlln, I wasn't sure that anything would happen here, but I've managed to push to this PR of yours. This commit (7dfb455) tidies up the removal of the "squeeze", which needs to go back in sometimes to get rid of size 1 dimensions that are not being regridded. Hope that's OK! (this commit can always be nuked, of course).

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davidhassell commented Sep 29, 2021

Hi @ThibHlln - I think we can merge this, now. I'll await your OK, though ...

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ThibHlln commented Sep 30, 2021 •
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Hi @davidhassell,

I was not sure what the squeezing was for, but I was guessing it would require more than just removing it.
Thank you for your help with this.

Yes, I think it can be merged now, I ran the tests above successfully after your commits.
So, it looks all good to me.

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davidhassell commented Sep 30, 2021

Hi @ThibHlln - I think the squeezing is all about making sure we pass the correctly shaped numpy array down to the ESMF layer. Thanks for your help with this. We expect a release of 3.11.0 in a couple of weeks (ish). Merging now ...

@davidhassell davidhassell merged commit f739b68 into NCAS-CMS:master Sep 30, 2021
@davidhassell davidhassell added this to the 3.11.0 milestone Sep 30, 2021
ThibHlln pushed a commit to ThibHlln/unifhy that referenced this pull request Oct 20, 2021
change dependency version for cf-python
c0c1b82 
This version includes:
- fix for memory leak due to ESMF objects NCAS-CMS/cf-python#225
- lift for size 1 restriction on grid NCAS-CMS/cf-python#249
- fix bug preventing cyclic domain (e.g. global runs) NCAS-CMS/cf-python#237
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Restrict size 1 dimension to source field in regridding

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@ThibHlln @davidhassell @sadielbartholomew