start_watch

START_WATCH

starts a StopWatch watch

SYNOPSIS
subroutine start_watch (watch, clock, err)

type (watchtype), intent(IN) :: watch

OR

type (watchtype), intent(IN) :: watch(:)

OR

type (watchgroup), intent(IN) :: watch

character(len=*), optional, intent(IN) :: clock

OR

character(len=*), optional, intent(IN) :: clock(:)

integer, optional, intent(OUT) :: err

DESCRIPTION
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.

DIAGNOSTICS
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:

0

No errors; execution successful.

1

Watch needs to be created. This error occurs if you attempt to start a watch that has been destroyed. The watch must first be created again. See also the comment about watches that have never been created in the BUGS section.

2

Watch is in the wrong state for this operation. This occurs when you attempt to start a watch that is currently running or paused.

4

Watch is in an unknown state. This occurs if StopWatch does not recognize the state (running, stopped, etc.) that the watch is in. This error should not occur, and indicates an internal bug in StopWatch .

8

Invalid clock type. This occurs if clock is present and one of the specified clocks is not supported by the implementation. See inquiry_stopwatch(3) to determine what clocks are available.

512

Failed to allocate required memory. When start_watch is called with an array or group of watches, temporary memory is allocated. This error occurs if the Fortran allocate statement returns a nonzero status indicating that memory could not be allocated. Avoid memory leaks by always destroying watches and groups before recreating them, and destroying local variable watches and groups before returning from a subroutine.

1024

Error occurred while deallocating memory. This error occurs if the Fortran deallocate statement returns a nonzero status while deallocating temporary memory used for an array or group of watches. The watches are started, but be aware that other problems could develop as a result of the deallocate error.

In addition to the run time diagnostics generated by StopWatch , the following problem may arise:

In Fortran 90, the character strings in an array constructor must all have the same length. Pad three letter clock names with a blank on the right to make a four character string, for example, 'cpu '.

EXAMPLES
type (watchtype) w1, w2(3)
type (watchgroup) g1
integer errcode

call start_watch(w1)
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.

BUGS
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.