I will tweet https://twitter.com/fortrantip about the block construct, a neat feature of Fortran 2008. A similar feature to discuss is the internal procedure. I don't use internal procedures often, since with host association it is not clear what the
inputs and outputs are, and since they don't foster modularity when they cannot be called except from the enclosing unit.

What are the benefits of internal procedures? What are some common use cases?

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"Beliavsky" wrote in message news:5c3eb8e9-e3b6-41d8-81e2-b353296381f7n@googlegroups.com...

I will tweet https://twitter.com/fortrantip about the block construct, a
neat
feature of Fortran 2008. A similar feature to discuss is the internal procedure.
I don't use internal procedures often, since with host association it is
not
clear what the inputs and outputs are, and since they don't foster
modularity when they cannot be called except from the enclosing unit.

What are the benefits of internal procedures? What are some common use
cases?

A common use case for me is to perform integration of a parameterized integrand. The enclosing subprogram sets the parameters in its local
variables and passes a procedure pointer to the internal function as an
actual argument to the integration procedure. When that procedure
invokes the internal procedure it gets the values of the parameters via
host association. This works in parallel code as well, provided the local variables don’t have the SAVE attribute.

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On Tuesday, March 1, 2022 at 12:06:14 AM UTC-5, James Van Buskirk wrote:

"Beliavsky" wrote in message

What are the benefits of internal procedures? What are some common use cases?

A common use case for me is to perform integration of a parameterized integrand. The enclosing subprogram sets the parameters in its local variables and passes a procedure pointer to the internal function as an actual argument to the integration procedure. When that procedure
invokes the internal procedure it gets the values of the parameters via
host association. This works in parallel code as well, provided the local variables don’t have the SAVE attribute.

Thanks. It will be fun to learn about procedure pointers and demonstrate
what you wrote :).

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James Van Buskirk <not_valid@comcast.net> schrieb:

"Beliavsky" wrote in message news:5c3eb8e9-e3b6-41d8-81e2-b353296381f7n@googlegroups.com...

I will tweet https://twitter.com/fortrantip about the block construct, a
neat
feature of Fortran 2008. A similar feature to discuss is the internal
procedure.
I don't use internal procedures often, since with host association it is
not
clear what the inputs and outputs are, and since they don't foster
modularity when they cannot be called except from the enclosing unit.

What are the benefits of internal procedures? What are some common use
cases?

A common use case for me is to perform integration of a parameterized integrand. The enclosing subprogram sets the parameters in its local variables and passes a procedure pointer to the internal function as an actual argument to the integration procedure. When that procedure
invokes the internal procedure it gets the values of the parameters via
host association. This works in parallel code as well, provided the local variables don’t have the SAVE attribute.

One problem is that this does not work from a normal module procedure.

For passing along info to integration routines, zero finders and so
on, my usual style is something like

module x
implicit none
type zero_type
real :: a, b, c
end type zero_type
contains
recursive function to_zero(x,parm) result(r)
real, intent(in) :: x
class(*), intent(in) :: parm
real :: r
select type(parm)
type is(zero_type)
r = parm%a + x*(parm%b+x*parm%c)
class default
error stop
end select
end function to_zero
end module x

If I'm worried about inefficiencies, LTO to the rescue :-)

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On Monday, February 28, 2022 at 8:38:20 PM UTC-8, Beliavsky wrote:

(snip)

What are the benefits of internal procedures? What are some common use cases?

Sometimes it is nice to have them near, even while not using or needing
host association. That is especially true when they are small, and forcing someone to search through a large project to find one isn't needed.

It isn't so obvious that they are more or less efficient than external procedures.

But yes, host association is nice sometimes.

Using internal procedures for actual arguments is a relatively new addition
to the standard, as internal procedures have been there much longer.

Before internal procedures, COMMON was used to get parameters into
routines passed as actual arguments. Well, until they were allowed as
actual arguments.

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"Thomas Koenig" wrote in message news:svkfea$p06$1@newsreader4.netcologne.de...

James Van Buskirk <not_valid@comcast.net> schrieb:

A common use case for me is to perform integration of a parameterized integrand. The enclosing subprogram sets the parameters in its local variables and passes a procedure pointer to the internal function as an actual argument to the integration procedure. When that procedure
invokes the internal procedure it gets the values of the parameters via host association. This works in parallel code as well, provided the
local
variables don’t have the SAVE attribute.

One problem is that this does not work from a normal module procedure.

Unless you are allowed the use of thread local storage...

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James Van Buskirk <not_valid@comcast.net> schrieb:

"Thomas Koenig" wrote in message news:svkfea$p06$1@newsreader4.netcologne.de...

James Van Buskirk <not_valid@comcast.net> schrieb:

A common use case for me is to perform integration of a parameterized
integrand. The enclosing subprogram sets the parameters in its local
variables and passes a procedure pointer to the internal function as an
actual argument to the integration procedure. When that procedure
invokes the internal procedure it gets the values of the parameters via
host association. This works in parallel code as well, provided the
local
variables don’t have the SAVE attribute.

One problem is that this does not work from a normal module procedure.

Unless you are allowed the use of thread local storage...

I'm not quite sure what use case you have in mind. TLS implies
multithreading, which standard Fortran does not have. Fortran
has either coarrays or, as an extension, OpenMP or OpenACC.

For the use case of recursively calling an integration routine
along several dimensions, for example, using TLS will not help.

What do you have in mind?

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