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| author | Janne Blomqvist <jb@gcc.gnu.org> | 2011-02-05 22:20:48 +0200 |
|---|---|---|
| committer | Janne Blomqvist <jb@gcc.gnu.org> | 2011-02-05 22:20:48 +0200 |
| commit | 4a9b1f8edc0c2e32ab238bfb28a8f14c8260f27c (patch) | |
| tree | 52835a001318abebf5837ab1091b95c7538024f5 /gcc/fortran | |
| parent | 9e7628863bc93aee7b54682e80401c2fc66a9b69 (diff) | |
| download | gcc-4a9b1f8edc0c2e32ab238bfb28a8f14c8260f27c.zip gcc-4a9b1f8edc0c2e32ab238bfb28a8f14c8260f27c.tar.gz gcc-4a9b1f8edc0c2e32ab238bfb28a8f14c8260f27c.tar.bz2 | |
PR 42434 Update SYSTEM_CLOCK documentation
From-SVN: r169854
Diffstat (limited to 'gcc/fortran')
| -rw-r--r-- | gcc/fortran/ChangeLog | 5 | ||||
| -rw-r--r-- | gcc/fortran/intrinsic.texi | 33 |
2 files changed, 29 insertions, 9 deletions
diff --git a/gcc/fortran/ChangeLog b/gcc/fortran/ChangeLog index 09606e1..b936715 100644 --- a/gcc/fortran/ChangeLog +++ b/gcc/fortran/ChangeLog @@ -1,3 +1,8 @@ +2011-02-05 Janne Blomqvist <jb@gcc.gnu.org> + + PR fortran/42434 + * intrinsic.texi (SYSTEM_CLOCK): Update documentation. + 2011-02-02 Janus Weil <janus@gcc.gnu.org> Paul Thomas <pault@gcc.gnu.org> diff --git a/gcc/fortran/intrinsic.texi b/gcc/fortran/intrinsic.texi index d8a97c5..f0287f6 100644 --- a/gcc/fortran/intrinsic.texi +++ b/gcc/fortran/intrinsic.texi @@ -11812,14 +11812,29 @@ and should considered in new code for future portability. @table @asis @item @emph{Description}: -Determines the @var{COUNT} of milliseconds of wall clock time since -the Epoch (00:00:00 UTC, January 1, 1970) modulo @var{COUNT_MAX}, -@var{COUNT_RATE} determines the number of clock ticks per second. -@var{COUNT_RATE} and @var{COUNT_MAX} are constant and specific to -@command{gfortran}. +Determines the @var{COUNT} of a processor clock since an unspecified +time in the past modulo @var{COUNT_MAX}, @var{COUNT_RATE} determines +the number of clock ticks per second. If the platform supports a high +resolution monotonic clock, that clock is used and can provide up to +nanosecond resolution. If a high resolution monotonic clock is not +available, the implementation falls back to a potentially lower +resolution realtime clock. + +@var{COUNT_RATE} and @var{COUNT_MAX} vary depending on the kind of the +arguments. For @var{kind=8} arguments, @var{COUNT} represents +nanoseconds, and for @var{kind=4} arguments, @var{COUNT} represents +milliseconds. Other than the kind dependency, @var{COUNT_RATE} and +@var{COUNT_MAX} are constant, however the particular values are +specific to @command{gfortran}. If there is no clock, @var{COUNT} is set to @code{-HUGE(COUNT)}, and -@var{COUNT_RATE} and @var{COUNT_MAX} are set to zero +@var{COUNT_RATE} and @var{COUNT_MAX} are set to zero. + +When running on a platform using the GNU C library (glibc), or a +derivative thereof, the high resolution monotonic clock is available +only when linking with the @var{rt} library. This can be done +explicitly by adding the @code{-lrt} flag when linking the +application, but is also done implicitly when using OpenMP. @item @emph{Standard}: Fortran 95 and later @@ -11832,11 +11847,11 @@ Subroutine @item @emph{Arguments}: @multitable @columnfractions .15 .70 -@item @var{COUNT} @tab (Optional) shall be a scalar of type default +@item @var{COUNT} @tab (Optional) shall be a scalar of type @code{INTEGER} with @code{INTENT(OUT)}. -@item @var{COUNT_RATE} @tab (Optional) shall be a scalar of type default +@item @var{COUNT_RATE} @tab (Optional) shall be a scalar of type @code{INTEGER} with @code{INTENT(OUT)}. -@item @var{COUNT_MAX} @tab (Optional) shall be a scalar of type default +@item @var{COUNT_MAX} @tab (Optional) shall be a scalar of type @code{INTEGER} with @code{INTENT(OUT)}. @end multitable |