8.2.25 _gfortran_caf_co_max — Collective maximum reduction

Description:

Calculates the for the each array element of the variable a the maximum value for that element in the current team; if result_image has the value 0, the result shall be stored on all images, otherwise, only on the specified image. This function operates on numeric values and character strings.

Syntax:

void _gfortran_caf_co_max (gfc_descriptor_t *a, int result_image, int *stat, char *errmsg, int a_len, int errmsg_len)

Arguments:
a intent(inout) And array descriptor with the data to be breoadcasted (on source_image) or to be received (other images).
result_image The ID of the image to which the reduced value should be copied to; if zero, it has to be copied to all images.
stat intent(out) Stores the status STAT= and may be NULL.
errmsg intent(out) When an error occurs, this will be set to an error message; may be NULL
a_len The string length of argument a.
errmsg_len the buffer size of errmsg.
NOTES

If result_image is nonzero, the value on all images except of the specified one become undefined; hence, the library may make use of this.

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https://gcc.gnu.org/onlinedocs/gcc-6.4.0/gfortran/_005fgfortran_005fcaf_005fco_005fmax.html