如何将过程指针用于具有不同参数个数的子例程 [英] How to use procedure pointers for subroutines with different number of arguments

问题描述

我正在开发Fortran计算科学计划。我想使用过程指针来分配问题中的边界条件，如下面的主程序所示：

 程序main 
使用边界
隐式无
 
 bc1 => boundaryA 
 bc2 =>边界B 
 bc3 => boundaryC 
 
 call comp_boundary 
 
结束程序
  

我在边界模块中定义了所有边界操作boundaryA / B / C

  module boundary 
 implicit none 
 
 procedure（boundary_type），pointer :: bc1，bc2，bc3 
 
抽象接口
子程序boundary_type（i）
 integer :: i 
结束子程序
结束接口
 
包含
 
子程序boundaryA（i）
 integer :: i 
 print *，'Boundary A at'，i 
结束子程序
 
子程序boundaryB（i）
整数:: i 
 print *，'边界B at'，i 
结束子程序
 
子程序boundaryC（i）
整数:: i 
 print *，'边界C at'，
结束子程序
 
子程序comp_boundary 
调用bc1（1）
调用bc2（2）
调用bc3（3）
结束子程序
 
结束模块
  

这个效果很好。

但是我的问题是，如果说 boundaryC 没有一个输入参数，而是两个，那么我的定义对于抽象接口 boundary_type 现在不起作用。

有可能使用过程指针来处理这种情况吗？或者任何其他方式？

解决方案

您可以通过 OPTIONAL 论据。这更多的是一种学术解决方案，因为总会有痛苦的节节。正如高性能Mark 指出，您决定使用一个或两个参数需要在某个地方完成。

尽管如此，可选参数需要添加这个全部的子程序，因此可能并不是真正的解决方案，因为所有的子程序都发生了根本性的变化。这与您给出的解决方案基本相同，只是使用了不同的过程参数集。

 模块边界
 IMPLICIT NONE 
 
 PROCEDURE（boundary_type），POINTER :: bc1，bc2 
 
抽象接口
 SUBROUTINE boundary_type（i，j）
 INTEGER :: i 
 INTEGER，可选:: j 
 END SUBROUTINE boundary_type 
 END INTERFACE 
 
 CONTAINS 
 
子程序boundaryA（i，j）
 INTEGER： ：i 
 INTEGER，可选:: j 
 PRINT *，'边界A at'，i 
 END SUBROUTINE boundaryA 
 
子程序boundaryB（i，j）
 INTEGER :: i 
 INTEGER，OPTIONAL :: j 
 PRINT *，'边界B at'，i，j 
 END子程序boundaryB 
 
子程序comp_boundary 
 CALL bc1（1）
 CALL bc2（2,3）
 END SUBROUTINE comp_boundary 
 
 END MODULE boundary 
  

注意： th e子程序 boundaryB must always 被两个参数调用，因为没有检查 j （使用 PRESENT ）

I'm developing a Fortran program for scientific computing. I want to use procedure pointers to assign the boundary conditions in the problem, shown in the following main program

program main
use boundary
implicit none

  bc1 => boundaryA
  bc2 => boundaryB
  bc3 => boundaryC

  call comp_boundary

end program

I define all the boundary operations "boundaryA/B/C" in a "boundary" module

module boundary
implicit none

procedure(boundary_type), pointer :: bc1,bc2,bc3

abstract interface
  subroutine boundary_type(i)
    integer :: i
  end subroutine
end interface

contains

subroutine boundaryA(i)
integer :: i
  print*, 'Boundary A at ',i
end subroutine

subroutine boundaryB(i)
integer :: i
  print*, 'Boundary B at ',i
end subroutine

subroutine boundaryC(i)
integer :: i
  print*, 'Boundary C at',i
end subroutine

subroutine comp_boundary
  call bc1(1)
  call bc2(2)
  call bc3(3)
end subroutine

end module

This works well.

But my question is that if, say, boundaryC has not one input argument, but two, then my definition for the abstract interface boundary_type doesn't work now.

Is that possible to use the procedure pointer to deal with this case? Or any other way around?

解决方案

You could achieve this with an OPTIONAL argument. This is more an academic solution as there is always conservation of misery. As the comment of High Performance Mark states, your decision to use one or two arguments will need to be made somewhere.

Nonetheless, the OPTIONAL argument would require to add this too all subroutines and could therefore be not really the solution you request as all subroutines are essentially changed. It is essentially the same solution you gave, with just different set of procedure arguments.

MODULE boundary
  IMPLICIT NONE

  PROCEDURE(boundary_type), POINTER :: bc1,bc2

  ABSTRACT INTERFACE
     SUBROUTINE boundary_type(i,j)
       INTEGER           :: i
       INTEGER, OPTIONAL :: j
     END SUBROUTINE boundary_type
  END INTERFACE

CONTAINS

  SUBROUTINE boundaryA(i,j)
    INTEGER           :: i
    INTEGER, OPTIONAL :: j
    PRINT *, 'Boundary A at ',i
  END SUBROUTINE boundaryA

  SUBROUTINE boundaryB(i,j)
    INTEGER           :: i
    INTEGER, OPTIONAL :: j
    PRINT *, 'Boundary B at ',i,j
  END SUBROUTINE boundaryB

  SUBROUTINE comp_boundary
    CALL bc1(1)
    CALL bc2(2,3)
  END SUBROUTINE comp_boundary

END MODULE boundary

Note: the subroutine boundaryB must always be called with both arguments as no check is done for the availability of j (using PRESENT)

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