starts a StopWatch
subroutine start_watch (watch, clock, err)
Starts the specified clocks of the specified watches. Any time previously accumulated in the clock is NOT cleared before starting. (Use reset_watch to clear accumulated time.)
One or more watches must be specified. The argument watch can be a single variable of type watchtype (see stopwatch(3)) to start one watch, an array of type watchtype to start several watches, or a variable of type watchgroup (see stopwatch(3)) to start the watches in a group.
The optional argument clock specifies which clocks to start on the specified watch(es). If omitted, the current default clocks (see option_stopwatch(3)) are started. If present, clock must be a character string containing 'cpu', 'user', 'sys', or 'wall', or an array of such character strings.
If present, the optional intent OUT integer argument err returns a status code. The code is the sum of the values listed below.
An error message will be printed to a specified I/O unit (unit 6 by default) if print_errors is TRUE (default is TRUE). The error message contains more detail about the cause of the error than can be obtained from just the status code, so you should set print_errors to TRUE if you have trouble determining the cause of the error.
If abort_errors is TRUE (default is FALSE), the program will terminate on an error condition. Otherwise, the program will continue execution but the watch(es) will not be started.
See option_stopwatch(3) for further information on print_errors, abort_errors and I/O units.
The relevant status codes and messages are:
In addition to the run time diagnostics generated by StopWatch
, the following
problem may arise:
type (watchtype) w1, w2(3)
type (watchgroup) g1
call start_watch(w2, err=errcode)
call start_watch(g1, (/'cpu ', 'wall'/), errcode)
The first call starts the default clocks on a single watch. The second call starts the default clocks on three watches given as an array and returns an status code. The third call starts the cpu and wall clocks on the watches in the group g1, and returns a status code.
It cannot be determined whether or not a watch variable or watch group has been created (passed as an argument to create_watch or create_watchgroup). If a watch or watch group that has never been created is passed into start_watch, it might generate a Fortran error due to passing a pointer with undefined association status to the Fortran intrinsic function associated. Some compilers will allow this as an extension to the Fortran 90 standard and recognize that the pointer is not associated, in which case the ``Watch needs to be created'' error message is generated.