MinGW and 3-digit exponents

[Rik]

11/12/13

I worked around the problem of failing tests because of 3-digit exponents
here (http://hg.savannah.gnu.org/hgweb/octave/rev/6a381b9ae055).

However, I went on to investigate whether PRINTF_EXPONENT_DIGITS carries a
performance penalty as claimed.  I found something like a 5% penalty, not a
300-400% penalty, so this might be a worthwhile option to turn on.

I used

x = rand (1e6, 1);
fid = fopen ("tst.txt", "wt");
tic; fprintf (fid, "%g\n", x); toc
fclose (fid)

Then I did the same test after using

setenv ("PRINTF_EXPONENT_DIGITS", "2")

I was running in a virtual machine and the timing precision on MinGW isn't
great, but the measured difference was small (~5%) with three runs for each
scenario.

I filed a report so that this doesn't get lost
(https://savannah.gnu.org/bugs/index.php?40562)

Cheers,
Rik