(CC: fortran@ as it relates to Fortran.)
Hi all,
On 1/7/20 12:16 PM, Tobias Burnus wrote:
in terms of the check, it looks fine to me – but I am not sure about
the spec.
* [OpenACC] Actually, I simply missed the bit (here: OpenACC 3; OpenACC
2.6 is same): “Any array or subarray in a data clause, including Fortran
array pointers, must be a contiguous block of memory, except for dynamic
multidimensional C arrays.” (2.7.1 under Restrictions).
* OpenMP (quoting TR8): “If a list item is an array section, it must
specify contiguous storage.” (2.22.7.1 map Clause under Restrictions).
However, that one seems to miss the case: “non_cont_ptr => A(::2); !$omp
... map(non_cont_ptr)” as non_cont_ptr is noncontiguous and an array but
not an array section.
In any case, those are restrictions imposed on the user – which the
compiler may or may not report. (A good one will, I presume. Although,
one can also regard it as implementation defined/vendor extension as GCC
will properly handle those – by mapping also the gaps.)
Cheers,
Tobias
At least the following test case seems to work fine:
integer :: A(10,10), out(12)
A = reshape([(i, i=0,100)], shape(A))
!$omp target map(A(3:6,3:5), out)
!$acc parallel copy(A(3:6,3:5), out)
out = reshape(A(3:6,3:5), shape(out))
A(3:6,3:5) = 4
!$acc end parallel
!$omp end target
print '(4i3)', out
print '(10i3)', A
end
The reason that it works is that the stride is included in the length
calculation:
#pragma omp target num_teams(1) thread_limit(0) map(tofrom:MEM[(c_char
*)_6] [len: _5])
Has for the section (with A(3:6,3:5) -> parm(1:4,1:3)):
parm.1.dim[0].lbound = 1;
parm.1.dim[0].ubound = 4;
parm.1.dim[0].stride = 1;
parm.1.dim[1].lbound = 1;
parm.1.dim[1].ubound = 3;
parm.1.dim[1].stride = 10;
And instead of doing '(4-1+1) * (3-1+1)' = 12 (i.e. multiplying the
extends),
the code does: 'stride * (3-1+1)' = 30.
Cheers,
Tobias
PS: It also works if one puts the stride on the ptr, i.e.:
integer,target :: A(10,10), out(12)
integer, pointer :: ptr(:,:)
A = reshape([(i, i=0,100)], shape(A))
ptr => A(3:6,3:5)
!$omp target map(ptr, out)
!$acc parallel copy(ptr, out)
out = reshape(ptr, shape(out))
ptr = 4
!$acc end parallel
!$omp end target
print '(4i3)', out
print '(10i3)', A
end
On 1/4/20 3:25 AM, Julian Brown wrote:
This patch tightens up error checking for array references used in
OpenACC clauses such that they must now be contiguous. I believe this
matches up to the spec (as of 2.6). I've tried to make it so an error
only triggers if the compiler is sure that a given array expression must
be non-contiguous at compile time, although this errs on the side
of potentially allowing the user to shoot themselves in the foot at
runtime: at least one existing test in the testsuite appears to expect
that behaviour.
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