[ncl-talk] sparse_matrix_mult

[Mary Haley]

Hi Mark,

It turns out the documentation was incorrect. I think when this function
was initially implemented, the thinking on missing values was a little
different and we documented it this way. However, when we actually released
the function, we decided that just because a column of X contained one more
missing values, this didn't mean that the whole addition should be missing.

I've fixed the two examples and added a new one.  Hopefully this makes more
sense.  I'm sorry for the confusion!

--Mary


On Thu, Dec 21, 2017 at 1:58 PM, Mary Haley <haley at ucar.edu> wrote:

> Hi Mark,
>
> I wanted to get back to you on this sooner.  This is definitely puzzling.
> I will take a closer look at the function to see if the documentation or
> the calculation is wrong.
>
> Thanks for bringing this up.  I will put a high priority on this
> (NCL-2708).
>
> --Mary
>
>
> On Mon, Dec 18, 2017 at 2:50 PM, mark collier via ncl-talk <
> ncl-talk at ucar.edu> wrote:
>
>> Hi,
>>
>> I've been testing out some features/applications of sparse_matrix_mult
>> and curious why the example doesn't replicate documentation, it could be
>> that the documentation is out of date.
>>
>>
>>
>> If I run example 1 from https://www.ncl.ucar.edu/
>> Document/Functions/Built-in/sparse_matrix_mult.shtml
>>
>>
>> I get:
>>
>>
>>
>>      bash-4.1$ ncl test_sparse.ncl
>>  Copyright (C) 1995-2017 - All Rights Reserved
>>  University Corporation for Atmospheric Research
>>  NCAR Command Language Version 6.4.0
>>  The use of this software is governed by a License Agreement.
>>  See http://www.ncl.ucar.edu/ for more details.
>>
>>    3.   6.   9.
>>   16.  20.  24.
>>   91. 104. 117.
>> ***************
>>
>>
>> Variable: y
>> Type: float
>> Total Size: 48 bytes
>>             12 values
>> Number of Dimensions: 2
>> Dimensions and sizes:   [4] x [3]
>> Coordinates:
>> Number Of Attributes: 1
>>   _FillValue :  9.96921e+36
>> (0,0)    3
>> (0,1)    6
>> (0,2)    9
>> (1,0)   16
>> (1,1)   20
>> (1,2)   24
>> (2,0)   91
>> (2,1)   104
>> (2,2)   117
>> (3,0)   9.96921e+36
>> (3,1)   9.96921e+36
>> (3,2)   9.96921e+36
>> bash-4.1$ ncl -V
>> 6.4.0
>> bash-4.1$ uname -a
>> Linux raijin1 3.10.0-693.5.2.el6.x86_64 #1 SMP Tue Oct 24 10:37:43 AEDT
>> 2017 x86_64 x86_64 x86_64 GNU/Linux​
>>
>> I have been using this function in relation to ESMF regridding, the
>> regridding seems to be working using this call but I am porting the weights
>> application to a python based approach and need to understand exactly what
>> the matrix multiplication is doing.
>>
>> Thanks for any advice
>> Mark.
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>
>
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