[Bug]: sum_rows() and sum_cols are reversed about dlib HOT 13 CLOSED

Maybe I can break it for you:

M:
1 2 3 
4 5 6 
7 8 9 

M has three rows:

1. 1 2 3
2. 4 5 6
3. 7 8 9

In order to sum the rows, we have to add the first row to the second row and then to the third row.

That means adding
1+4+7, 2+5+8, 3+6+9

If you take the first row (1 2 3) and add the elements together, you are not adding the rows, you are adding the columns. If you write the loops to do that, you'll see that when you do the addition, the row index stays constant, and the column index changes: you are adding the columns.

from dlib.

This?

M:
1 2 3 
4 5 6 
7 8 9 

Sum of Rows:
12 15 18 

Sum of Cols:
 6 
15 
24 

That's the right output. sum_rows() adds all the row vectors together, which gives the result you have there from your program.

from dlib.

I am very glad how kind you respond to my issue! (I also made ..let's say, "other experiences".) I feel very sorry, that I flagged my issue directly as "Bug". I should have started a discussion or opened a normal issue.

from dlib.

Yeah, updated the docs. Can't rename the functions though, too much code and people are using the current names :D

from dlib.

After reading the documentation, it seems to me like it's working as intended.

from dlib.

I read

    const matrix_exp sum_rows (
        const matrix_exp& m
    );
    /*!
        requires
            - m.size() > 0
        ensures
            - returns a row matrix that contains the sum of all the rows in m. 
            - returns a matrix M such that
                - M::type == the same type that was in m
                - M.nr() == 1
                - M.nc() == m.nc()
                - for all valid i:
                    - M(i) == sum(colm(m,i)) 
    !*/

especially sum(colm(m, i)) as a sum over column i of matrix m, although the function is called sum_rows and the first sentence says that it "returns a row matrix that contains the sum of all the rows in m." I can't exclude mistakes on my side. I'm glad for clarification.

Source:

from dlib.

Yep, it's doing what it's supposed to do :)

from dlib.

Then I'm puzzled. When sum_rows() and sum_cols() work appropriately, am I reading the output of my example program incorrectly?

from dlib.

Although I closed the issue, I want to give some feedback—you can freely decide, what you will do with it!

For me "sum of all the rows" still sounds more like I thought in the first place (but I am obviously biased). Hence, the documentation, ie. sum(colm(m, i)), looked contradictory. I would advocate for a less ambiguous description. In case you agree, I can try my best and submit a PR.

from dlib.

No worries.

What if it said "sum of all the row vectors", that clearer?

from dlib.

Yes, definitely! 🚀

(In my opinion, sum_row_vectors() additionally as function name would be even better but I guess this is not feasible due to backwards compatibility, ie. deleting/changing the name sum_rows() is a big nono. 😄)

from dlib.

Nice!

... As mentioned, I can fully understand a renaming is out of scope.. but we all have hopes and wishes! :D

To conclude: Thank you for the nice conversation on my fake bug! :)

from dlib.

My pleasure :D

from dlib.