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Re: (Partial) implementation of new math encodings
- To: firstname.lastname@example.org
- Subject: Re: (Partial) implementation of new math encodings
- From: "Nelson H. F. Beebe" <email@example.com>
- Date: Wed, 23 Apr 1997 11:18:03 -0600 (MDT)
- Cc: firstname.lastname@example.org
Matthias Clasen <email@example.com> writes:
>> I was really thinking of a comparison of the graphical output: perhaps
>> more along the lines of using pstopnm on a ps file and then comparing
>> the resulting pbm files with pnmarith -difference. I don't know if that
>> will produce any useful information (as I haven't tried it yet).
Several months ago, I set up a test suite for ghostscript (for
which I'm an alpha tester) to do this sort of thing: produce
a bitmap representation of the output for a substantial collection
of PostScript files, and then check for differences. It turned
out to be infeasible: even a change in optimization level on
the same machine could produce substantial differences in the
output that made the diffs useless. A visual comparision of
the screen images from the two versions would not uncover
any differences. I discussed this with L. Peter Deutsch,
the ghostscript developer, but we did not find a suitable
solution. There is one commercial test suite for PostScript,
but its cost is too high for the ghostscript developers.
Thus, I'm sceptical that diff'ing bitmaps would produce
output that a human could reasonably interpret. Even though
TeX works internally almost exclusively in 32-bit integer
arithmetic, PostScript renderers have a LOT of floating-point,
and this may lead to more differences than would be expected.
I therefore think a comparison of the output of dvitype or
dv2dt would be a better way, since that would avoid the
introduction of machine-sensitive floating-point arithmetic.
This approach also has the advantage of not requiring software
that is not part of standard TeX distributions.
Nelson H. F. Beebe Tel: +1 801 581 5254
Center for Scientific Computing FAX: +1 801 581 4148
Department of Mathematics, 105 JWB Internet: firstname.lastname@example.org
University of Utah URL: http://www.math.utah.edu/~beebe
Salt Lake City, UT 84112, USA