Fortran - Type Declarations using kind

Author

Type Declarations using kind

luis

2005-02-07, 4:03 pm

my type declaration statement for real is:
real(4) or real(8)

in a public code i found

integer(4),parameter :: k = kind(0.0d0)
real(kind=k)::xc

What does "0.0d0" means

Thanks in advance

Luis Solis

beliavsky@aol.com

2005-02-07, 4:03 pm

luis wrote:
> my type declaration statement for real is:
> real(4) or real(8)
>
> in a public code i found
>
> integer(4),parameter :: k = kind(0.0d0)
> real(kind=k)::xc
>
> What does "0.0d0" means

It means 0.0 as a double precision constant. For a compiler where the
default real has kind of 4 (most common),

print*,kind(0.0),kind(0.0d0)

gives

4 8

Jan Vorbrüggen

2005-02-08, 9:01 am

> integer(4),parameter :: k = kind(0.0d0)
> real(kind=k)::xc
>
> What does "0.0d0" means

That having been explained, let me note that while the above code goes
in the right direction, it gets a crucial detail wrong: The declaration
of k should not contain the (4). The whole point of this construct is
to make it indepedent of whatever KIND numbering system the compiler
uses, but the (4) selects one such system again. Just get rid of it
- KIND numbers are defined to be of default integer kind in any case
(I hope just for the above reason 8-)).

Jan

luis

2005-02-08, 9:01 am

Jan Vorbrüggen wrote:
>
>
> That having been explained, let me note that while the above code goes
> in the right direction, it gets a crucial detail wrong: The declaration
> of k should not contain the (4). The whole point of this construct is
> to make it indepedent of whatever KIND numbering system the compiler
> uses, but the (4) selects one such system again. Just get rid of it
> - KIND numbers are defined to be of default integer kind in any case
> (I hope just for the above reason 8-)).
>
> Jan
ok
integer,parameter :: DP = kind(0.0d0)
real(kind=DP)::xc

Could i declare integer(1), integer(4) or integer(8) in a similar way ?

Luis

Michael Metcalf

2005-02-08, 9:01 am

"luis" <lsolis@mu.intecsa-inarsa.es> wrote in message
news:cJ0Od.225560$A7.322425@telenews.teleline.es...
> integer,parameter :: DP = kind(0.0d0)
> real(kind=DP)::xc
>
> Could i declare integer(1), integer(4) or integer(8) in a similar way ?
>

Here's what we suggest in "Fortran 90/95 Explained" (Section 5.5), if you
really need to specify kinds that are not default:

module numeric_kinds
! named constants for 4, 2, and 1 byte integers:
integer, parameter :: &
i4b = selected_int_kind(9), &
i2b = selected_int_kind(4), &
i1b = selected_int_kind(2)
! and for single, double and quadruple precision reals:
integer, parameter :: &
sp = kind(1.0), &
dp = selected_real_kind(2*precision(1.0_sp)), &
qp = selected_real_kind(2*precision(1.0_dp))
end module numeric_kinds

If you use exclusively default kinds (usually 4 bytes), you don't need any
kind specification.

Regards,

Mike Metcalf

Sponsored Links