Understanding Fortran Templates and Compiler-Driven Design Goals

Delve into the world of Fortran templates through a primer on generics, showcasing design goals set by the compiler. Explore syntax examples and motivating examples such as the AXPY subroutine, offering insight into the self-consistent nature of templates and their flexibility in parameter combinations.

• Fortran
• Templates
• Compiler
• Generics
• Design Goals

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1. Fortran Templates A Primer J3 Generics Subgroup

2. Template Design Goals Compiler ensures the template is: Self consistent Specifies what makes a valid combination of parameters Work with derived and intrinsic types Template doesn t dictate spelling

3. Some Example Syntax REQUIREMENT fizz(T, buzz) TYPE, DEFERRED :: T FUNCTION buzz( ) END FUNCTION END REQUIREMENT TEMPLATE foo(bar, baz, ) REQUIRES fizz(bar, baz) END TEMPLATE INSTANTIATE foo(integer, operator(+), ), ONLY: a, b => c,

4. A Motivating Example: AXPY subroutine axpy(a, x, y) real, intent(in) :: a real, intent(in) :: x(:) real, intent(inout) :: y(:) y = a * x + y end subroutine

5. A Motivating Example: AXPY (cont) template axpy_tmpl(k) integer, parameter :: sp = kind(1.0), dp = kind(1.d0) private instantiate axpy_tmpl(sp) public :: axpy instantiate axpy_tmpl(dp) integer, constant :: k real(sp) :: a, x(10), y(10) interface axpy real(dp) :: da, dx(10), dy(10) procedure axpy_ end interface call axpy(a, x, y) contains call axpy(da, dx, dy) subroutine axpy_(a, x, y) real(k), intent(in) :: a real(k), intent(in) :: x(:) real(k), intent(inout) :: y(:) y = a * x + y end subroutine end template

6. A Motivating Example: AXPY (cont) template axpy_tmpl(T, plus, times) requirement bin_op(T, op) private type, deferred :: T integer, parameter :: sp = kind(1.0), dp = kind(1.d0) public :: axpy elemental function op(a, b) instantiate axpy_tmpl(real(sp), operator(+), operator(*)) requires bin_op(T, plus) type(T), intent(in) :: a, b instantiate axpy_tmpl(real(dp), operator(+), operator(*)) requires bin_op(T, times) type(T) :: op instantiate axpy_tmpl(integer, operator(+), operator(*)) interface axpy end function real(sp) :: a, x(10), y(10) procedure axpy_ end requirement real(dp) :: da, dx(10), dy(10) end interface integer :: ia, ix(10), iy(10) contains subroutine axpy_(a, x, y) call axpy(a, x, y) type(T), intent(in) :: a call axpy(da, dx, dy) type(T), intent(in) :: x(:) call axpy(ia, ix, iy) type(T), intent(inout) :: y(:) y = plus(times(a, x), y) end subroutine end template

7. A Motivating Example: AXPY subroutine axpy(a, x, y) real, intent(in) :: a real, intent(in) :: x(:) real, intent(inout) :: y(:) y = a * x + y end subroutine

8. A Motivating Example: AXPY (cont) template axpy_tmpl(T, U, V, plus, times) requirement bin_op(T, U, V, op) integer, parameter :: sp = kind(1.0), dp = kind(1.d0) private type, deferred :: T, U, V instantiate axpy_tmpl( & public :: axpy elemental function op(a, b) real(sp), integer, real(dp), operator(+), operator(*)) requires bin_op(T, U, U, times) type(T), intent(in) :: a real(sp) :: a requires bin_op(U, V, V, plus) type(U), intent(in) :: b integer :: x(10) interface axpy type(V) :: op real(dp) :: y(10) procedure axpy_ end function end interface end requirement call axpy(a, x, y) contains subroutine axpy_(a, x, y) type(T), intent(in) :: a type(U), intent(in) :: x(:) type(V), intent(inout) :: y(:) y = plus(times(a, x), y) end subroutine end template

9. Thank You