[Octave-bug-tracker] [bug #46417] GL2PS info: OpenGL feedback buffer overflow when printing

[Rik]

Follow-up Comment #20, bug #46417 (project octave):

@Panxto: I think you're correct that the starting buffer size of 1MB is way
too small.  How about a starting size of 4MB?

Another question is whether the buffer size should grow linearly or
exponentially?  If the first round fails at 4MB is it really likely to succed
at 5 MB? or should we be increasing by a scale factor like 1.5 or 2 each time
through the loop?  From my earlier experiments, a pcolor plot requires a fixed
75 bytes per pixel.  Given that this is a 2-D image, a linear growth in the
length of a side of the image requires a squared growth in memory
requirements.  If we change the code to


buffsize *= 2;


Then Octave will be growing linearly in image size.  I think this will also
help the underlying malloc() call to have memory requirements that are aligned
to powers of 2.

To make it concrete,


starting_img_size = sqrt ((4 * 1024 * 1024) / 75) = 236 x 236
img_size_1 = sqrt ((8 * 1024 * 1024) / 75) = 334 x 334
img_size_2 = sqrt ((16 * 1024 * 1024) / 75) = 473 x 473
img_size_3 = sqrt ((32 * 1024 * 1024) / 75) = 669 x 669




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