Re: Floating point performance (was Re: compiling LUA for uClinux)

[Mike Pall <mikelu-0504@...>]

Hi,

Adam D. Moss wrote:
> On a similar note, poking around in luaconf.h I tried turning
> lua_number2str()'s sprintf() into a gcvt() to see if that
> gained anything.  But it was actually slightly slower than
> sprintf() (which was a bit surprising because intuitively sprintf
> has to do more work, but sprintf has probably been subject to more
> optimization).

$ man gcvt | ul -Tunknown | grep -A2 NOTES
NOTES
       This function is obsolete. Instead, sprintf() is recommended.

$ tail -9 glibc-2.3.3/misc/efgcvt.c
char *
APPEND (FUNC_PREFIX, gcvt) (value, ndigit, buf)
     FLOAT_TYPE value;
     int ndigit;
     char *buf;
{
  sprintf (buf, "%.*" FLOAT_FMT_FLAG "g", MIN (ndigit, NDIGIT_MAX), value);
  return buf;
}

Bye,
     Mike