projects / thirdparty / gcc.git / blame
| Commit | Line | Data |
|---|---|---|
| c63539ff ML |
1 | .. |
| 2 | Copyright 1988-2022 Free Software Foundation, Inc. | |
| 3 | This is part of the GCC manual. | |
| 4 | For copying conditions, see the copyright.rst file. | |
| 5 | ||
| 6 | .. _co_max: | |
| 7 | ||
| 8 | CO_MAX --- Maximal value on the current set of images | |
| 9 | ***************************************************** | |
| 10 | ||
| 11 | .. index:: CO_MAX, Collectives, maximal value | |
| 12 | ||
| 13 | .. function:: CO_MAX(A, RESULT_IMAGE, STAT, ERRMSG) | |
| 14 | ||
| 15 | ``CO_MAX`` determines element-wise the maximal value of :samp:`{A}` on all | |
| 16 | images of the current team. If :samp:`{RESULT_IMAGE}` is present, the maximum | |
| 17 | values are returned in :samp:`{A}` on the specified image only and the value | |
| 18 | of :samp:`{A}` on the other images become undefined. If :samp:`{RESULT_IMAGE}` is | |
| 19 | not present, the value is returned on all images. If the execution was | |
| 20 | successful and :samp:`{STAT}` is present, it is assigned the value zero. If the | |
| 21 | execution failed, :samp:`{STAT}` gets assigned a nonzero value and, if present, | |
| 22 | :samp:`{ERRMSG}` gets assigned a value describing the occurred error. | |
| 23 | ||
| 24 | :param A: | |
| 25 | shall be an integer, real or character variable, | |
| 26 | which has the same type and type parameters on all images of the team. | |
| 27 | ||
| 28 | :param RESULT_IMAGE: | |
| 29 | (optional) a scalar integer expression; if | |
| 30 | present, it shall have the same value on all images and refer to an | |
| 31 | image of the current team. | |
| 32 | ||
| 33 | :param STAT: | |
| 34 | (optional) a scalar integer variable | |
| 35 | ||
| 36 | :param ERRMSG: | |
| 37 | (optional) a scalar character variable | |
| 38 | ||
| 39 | Standard: | |
| 40 | Technical Specification (TS) 18508 or later | |
| 41 | ||
| 42 | Class: | |
| 43 | Collective subroutine | |
| 44 | ||
| 45 | Syntax: | |
| 46 | .. code-block:: fortran | |
| 47 | ||
| 48 | CALL CO_MAX(A [, RESULT_IMAGE, STAT, ERRMSG]) | |
| 49 | ||
| 50 | Example: | |
| 51 | .. code-block:: fortran | |
| 52 | ||
| 53 | program test | |
| 54 | integer :: val | |
| 55 | val = this_image () | |
| 56 | call co_max (val, result_image=1) | |
| 57 | if (this_image() == 1) then | |
| 58 | write(*,*) "Maximal value", val ! prints num_images() | |
| 59 | end if | |
| 60 | end program test | |
| 61 | ||
| 62 | See also: | |
| 63 | :ref:`CO_MIN`, | |
| 64 | :ref:`CO_SUM`, | |
| 65 | :ref:`CO_REDUCE`, | |
| 3ed1b4ce | 66 | :ref:`CO_BROADCAST` |