Question: The OpenAcc directive "!$acc parallel loop" does not work in Community Edition 19.4

Accelerated Computing HPC Compilers Legacy PGI Compilers
1

The Community Edition 19.4 was just installed. A small test on OpenAcc was performed:

program testOpenAcc
implicit none

integer::i
integer::N
real(8)::a(10000)
a=0.0D+00
N=1000
write(*,*)a(1:5)
write(*,*)'Hello world!'
	!$acc data copyin(N,i,a(1:N))
	!$acc parallel loop
	do i=1,N
		a(i)=1.0D+00
	enddo
	!$acc end parallel loop
	
	!$acc update self(a(1:N))
	!$acc end data
write(*,*)a(1:5)
end program testOpenAcc

The output was as follows:

0.000000000000000 0.000000000000000 0.000000000000000
0.000000000000000 0.000000000000000
Hello world!
Failing in Thread:1
call to cuStreamSynchronize returned error 719: Launch failed (often invalid pointer dereference)

Failing in Thread:1
call to cuMemFreeHost returned error 719: Launch failed (often invalid pointer dereference)

The directive ‘!$acc parallel loop’ can work on Community Edition 18.4, but it can not work on the present version, i.e., Community Edition 19.4.

Can you help find the reason?

Thanks a lot!

Jingbo

2

Hi Jingbo,

It looks like a problem where the compiler isn’t ignoring the “i” in the data clause. It should since the loop index variable is implicitly private and making it shared (the default behavior of a data clause) would cause this type of runtime error. I added a problem report TPR#27410 and sent it to our engineers to investigate.

The work around is to remove “i” from the copyin clause (N isn’t needed either so I removed it as well).

% cat test.f90
program testOpenAcc
implicit none

integer::i
integer::N
real(8)::a(10000)
a=0.0D+00
N=1000
write(*,*)a(1:5)
write(*,*)'Hello world!'
        !$acc data copyin(a(1:N))
        !$acc parallel loop
        do i=1,N
                a(i)=1.0D+00
        enddo
        !$acc end parallel loop

        !$acc update self(a(1:N))
        !$acc end data
write(*,*)a(1:5)
end program testOpenAcc
% pgf90 test.f90 -ta=tesla -Minfo=accel -V19.4; a.out
testopenacc:
     11, Generating copyin(a(:n))
     12, Generating Tesla code
         13, !$acc loop gang, vector(128) ! blockidx%x threadidx%x
     18, Generating update self(a(:n))
    0.000000000000000         0.000000000000000         0.000000000000000
    0.000000000000000         0.000000000000000
 Hello world!
    1.000000000000000         1.000000000000000         1.000000000000000
    1.000000000000000         1.000000000000000

Hope this helps,
Mat

3

Dear Mat,

Thank you for your comments!

It works very well!

Regards,

Jingbo

4

TPR 27410 is resolved w/20.1