Intel® Fortran Compiler Classic and Intel® Fortran Compiler Developer Guide and Reference

ID 767251
Date 3/22/2024
Public

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Document Table of Contents

qopt-streaming-stores, Qopt-streaming-stores

Enables generation of streaming stores for optimization.

Syntax

Linux:

-qopt-streaming-stores=keyword

-qno-opt-streaming-stores

Windows:

/Qopt-streaming-stores:keyword

/Qopt-streaming-stores-

Arguments

keyword

Specifies whether streaming stores are generated. Possible values are:

always

Enables generation of streaming stores for optimization. The compiler optimizes under the assumption that the application is memory bound.

When this option setting is specified, it is your responsibility to also insert any memory barriers (fences) as required to ensure correct memory ordering within a thread or across threads. See the Examples section for one way to do this.

never

Disables generation of streaming stores for optimization. Normal stores are performed.

This setting has the same effect as specifying -qno-opt-streaming-stores or /Qopt-streaming-stores-.

auto

Lets the compiler decide which instructions to use.

Default

-qopt-streaming-stores=auto
or /Qopt-streaming-stores:auto

The compiler decides whether to use streaming stores or normal stores.

Description

This option enables generation of streaming stores for optimization. This method stores data with instructions that use a non-temporal buffer, which minimizes memory hierarchy pollution.

This option may be useful for applications that can benefit from streaming stores.

IDE Equivalent

None

Alternate Options

None

Example

The following example shows one way to insert memory barriers (fences) when specifying -qopt-streaming-stores=always or /Qopt-streaming-stores:always. It uses the procedure interface for_sfence from the module IFCORE, which maps to the C/C++ function _mm_sfence:

program main
  implicit none

  INTEGER, PARAMETER :: dp = selected_real_kind(15, 307)
  integer, parameter :: k5 = selected_int_kind(5)
  integer, parameter :: k15 = selected_int_kind(15)
  integer (kind=k5), parameter  :: i5 = 10
  integer (kind=k15) :: i15
  integer (kind=k15) :: sizeof
  REAL (KIND=dp) :: a(i5)
  REAL (KIND=dp) :: b(i5)
  REAL (KIND=dp) :: c(i5)

  sizeof = size(a) 
  call sub1(a,b,c,sizeof,sizeof,sizeof)

  contains
    
  subroutine sub1(a, b, c, lent, n1, n2)
  use IFCORE, only : for_sfence
  integer (kind=k15) lent, n1, n2, i, j
  REAL (KIND=dp) a(lent), b(lent), c(lent), d(lent)
  !$omp parallel do
  do j = 1, n1
      a(j) = 1.0 *j
      b(j) = 2.0 * j*j
      c(j) = 3.0 *j * j*j
  enddo
  !$omp end parallel do
  call for_sfence()
  !$omp parallel do
  do i = 1, n2
      a(i) = a(i) + b(i) * c(i)
      write(*,*)a(i)
  enddo
  !$omp end parallel do
  end subroutine

  end

See Also