[Octave-bug-tracker] [bug #40562] Consider using PRINTF_EXPONENT_DIGITS on MinGW

[Rik]

URL:
  <http://savannah.gnu.org/bugs/?40562>

                 Summary: Consider using PRINTF_EXPONENT_DIGITS on MinGW
                 Project: GNU Octave
            Submitted by: rik5
            Submitted on: Tue 12 Nov 2013 08:34:09 PM PST
                Category: Libraries
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Feature Request
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: dev
        Operating System: Microsoft Windows

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Details:

I worked around the problem of failing tests on MinGW 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.




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