m_delay_file_access.f90

Go to the documentation of this file.

!>
!! @file
!! @brief Contains module m_delay_file_access
 
!> @brief Rank-staggered file access delays to prevent I/O contention on parallel file systems
module m_delay_file_access
    use m_precision_select
    implicit none
    private
 
    public :: delayfileaccess
 
    integer, private, parameter :: &
        n_processes_file_access = 128, &
        file_access_delay_unit = 10000
 
contains
 
    !> @brief Introduces a rank-dependent busy-wait delay to stagger parallel file access and reduce I/O contention.
    impure subroutine delayfileaccess(ProcessRank)
        integer, intent(in) :: processrank
 
        integer :: idelay, nfileaccessdelayiterations
        real(wp) :: number, dummy
 
        nfileaccessdelayiterations &
            = (processrank/n_processes_file_access)*file_access_delay_unit
 
        do idelay = 1, nfileaccessdelayiterations
            ! Wait my turn
            call random_number(number)
            dummy = number*number
        end do
 
    end subroutine delayfileaccess
 
end module m_delay_file_access