bugGNU Octave - Bugs: bug #55077, automatic broadcasting for dot...


bug #55077: automatic broadcasting for dot product

Submitter:  CarnĂ« Draug <carandraug>
Submitted:  Fri 23 Nov 2018 11:56:37 AM UTC
Category:  Octave Function Severity:  1 - Wish
Priority:  3 - Low Item Group:  Feature Request
Status:  Confirmed Assigned to:  None
Originator Name:  Open/Closed:  * Open
Release:  * dev Operating System:  * Any
Fixed Release:  None Planned Release:  None
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Sat 24 Nov 2018 02:51:36 AM UTC, comment #1: 

Matlab doesn't broadcast (https://www.mathworks.com/help/matlab/ref/dot.html), but I think your interpretation makes a lot of sense.

It would be nicer to use a for loop in dot.cc, rather than repmat which would require more memory usage (if only temporarily).

Rik <rik5>
Project Administrator
Fri 23 Nov 2018 11:56:37 AM UTC, original submission:  

I'm thinking it would be nice if automatic broadcasting also worked in the dot function, so it would compute dot product between one and many vectors. Like so:

>> a = [1; 2];
>> b = [4; 5];
>> c = [6; 7];
>> dot (a, b, 1)
ans =  14
>> dot (a, c, 1)
ans =  20
>> dot (a, [b c], 1) # currently it fails
error: dot: sizes of X and Y must match

>> dot (repmat (a, 1, 2), [b c], 1) # could work like this
ans =

   14   20

## And for this very simple case, this already works if we don't use dot at all
>> a' * [b c]
ans =

   14   20

Carnë Draug <carandraug>
Project Member


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    Follow 3 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2018-11-24 rik5 Severity3 - Normal 1 - Wish
        Priority5 - Normal 3 - Low
        StatusNone Confirmed

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