[Octave-bug-tracker] [bug #38085] image package: fails to build with --enable-64 (entropyfilt)

[Carnë Draug]

Follow-up Comment #12, bug #38085 (project octave):

> After some trials, it was possible to get the code to compile on Linux amd64
+ gcc-4.9.2 changing those two lines to:
>
> hist (((int)((int)(vals (i)))) + ((int)add)) ++;
>
> hist ((((int)(int)(vals (i)))) + ((int)add)) /= (double)len; 

More important than being able to compile the code, does it still return
correct results? That function doesn't have any tests so it's hard for me to
test it. I have confirmed that it is not Matlab compatible but that is by
design (and will have to be fixed later).

You seem to care about this function so I can assume that you have test cases
for this function. Can you please confirm that the function still behaves
properly?

> As additional info, using bwlabeln needs 19 Gbytes of working mem RAM to be
capable of processing 1,3 GigaVoxel grayscale (uint8) data. bwconncomp ++
labelmatrix needs "only" 5 Gbytes. Does it seem reasonable?

bwlabeln is known to use more memory as it uses union-find (it is meant to be
faster than bwconncomp on specific types of images but I haven't come across
of such type yet).  It also returns a matrix of class double (required for
Matlab compatibility) so the return value of such image will be 10.4Gbytes.
The way we work around border elements required a duplicate of the image. 
There are other approaches but they'll be slower. I would appreciate if you
could implement alternatives.

If bwconncomp is faster and more memory efficient for you, use it.

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