Dear Ioannis, this is my experience with offloading using omp4... it is slightly out of date but i suspect syntax did not change. in the module that contains the data (i suspect in reality is a glorified common block) you need things like this ``` !$omp declare target(xxx,yyy,zzz,vxx,vyy,vzz,fxx,fyy,fzz) ``` then of course you will need to sync the data to device before the call of the routine ``` !$omp target map(to: imcon) & !$omp map(to: xxx,yyy,zzz) ``` Regards, Alin Without Questions there are no Answers! ______________________________________________________________________ Dr. Alin Marin ELENA http://alin.elena.space/ ______________________________________________________________________ On Sat, 5 Sep 2020 at 15:35, Ioannis E. Venetis <venetis@xxxxxxxxxxxxxxx> wrote: > > Any comment on this? Are global variables defined in a module and used > in subroutines in the target region supported through the declare target > link mechanism currently on gcc? If so, am I doing something wrong on > how to use that mechanism? If not, is there any other approach I could > follow without too many changes in the code? In the real code I have > about 20 such variables and the call tree in the target region goes up > to 3 subroutines deep. > > Ioannis E. Venetis > > On 3/9/2020 9:36 μ.μ., Ioannis E. Venetis wrote: > > Hello everyone, > > > > I have a larger program that I am trying to convert so that the > > computationally intensive part will run on an NVidia GPU using OpenMP. > > However, I am running into trouble when compiling the program. The > > part of the program to run on the GPU contains calls to subroutines, > > where variables declared in a separate module are used. This seems to > > be creating issues. I have reduced the problem to the attached files. > > > > I compile as follows: > > > > gfortran test_link.f90 common_vars.f90 parameters.f90 -O0 -fopenmp > > -Wall -Wextra -o test_link > > > > With the file test_link.f90 as attached, the program compiles and runs > > without a problem. > > > > If I remove the comments for the subroutine TEST() and comment out > > line 31 in test_link.f90 (the line "I = NR") the compilation gives the > > following error: > > > > ptxas /tmp/ccw3FqJD.o, line 52; error : Illegal operand type to > > instruction 'ld' > > ptxas /tmp/ccw3FqJD.o, line 52; error : Unknown symbol > > '__common_vars_MOD_nr$linkptr' > > ptxas fatal : Ptx assembly aborted due to errors > > nvptx-as: ptxas returned 255 exit status > > mkoffload: fatal error: > > /home/myself/apps/gcc-10.2.0/bin/x86_64-pc-linux-gnu-accel-nvptx-none-gcc > > returned 1 exit status > > compilation terminated. > > lto-wrapper: fatal error: > > /home/myself/apps/gcc-10.2.0/libexec/gcc/x86_64-pc-linux-gnu/10.2.0//accel/nvptx-none/mkoffload > > returned 1 exit status > > compilation terminated. > > /usr/bin/ld: error: lto-wrapper failed > > collect2: error: ld returned 1 exit status > > > > Is this a bug in gfortran or have I misunderstood how DECLARE TARGET > > LINK works in combination with using subroutines? > > > > And a last point: If I use -O3 during compilation the program compiles > > and runs fine in both cases. I assume that TEST() is inlined in this > > case and the error disappears? > > > > Any help to overcome this issue is more than welcome. > > > > Best regards, > > > > Ioannis E. Venetis > > > > PS1: The problem happens with gcc 10.2 that I compiled myself: > > > > $ ~/apps/gcc-10.2.0/bin/gfortran -v > > Using built-in specs. > > COLLECT_GCC=/home/myself/apps/gcc-10.2.0/bin/gfortran > > COLLECT_LTO_WRAPPER=/home/myself/apps/gcc-10.2.0/libexec/gcc/x86_64-pc-linux-gnu/10.2.0/lto-wrapper > > > > OFFLOAD_TARGET_NAMES=nvptx-none > > Target: x86_64-pc-linux-gnu > > Configured with: ../gcc-10.2.0/configure > > --enable-offload-targets=nvptx-none > > --with-cuda-driver-include=/usr/local/cuda/include > > --with-cuda-driver-lib=/usr/local/cuda/lib64 --disable-bootstrap > > --disable-multilib --enable-languages=c,c++,fortran,lto > > --prefix=/home/myself/apps/gcc-10.2.0 > > Thread model: posix > > Supported LTO compression algorithms: zlib > > gcc version 10.2.0 (GCC) > > > > > > PS2: Same problem also happens with gcc 9.3 as installed on Ubuntu > > 16.04 from apt: > > > > $ gfortran -v > > Using built-in specs. > > COLLECT_GCC=gfortran > > COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/9/lto-wrapper > > OFFLOAD_TARGET_NAMES=nvptx-none:hsa > > OFFLOAD_TARGET_DEFAULT=1 > > Target: x86_64-linux-gnu > > Configured with: ../src/configure -v --with-pkgversion='Ubuntu > > 9.3.0-10ubuntu2~16.04' > > --with-bugurl=file:///usr/share/doc/gcc-9/README.Bugs > > --enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++,gm2 > > --prefix=/usr --with-gcc-major-version-only --program-suffix=-9 > > --program-prefix=x86_64-linux-gnu- --enable-shared > > --enable-linker-build-id --libexecdir=/usr/lib > > --without-included-gettext --enable-threads=posix --libdir=/usr/lib > > --enable-nls --enable-clocale=gnu --enable-libstdcxx-debug > > --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new > > --enable-gnu-unique-object --disable-vtable-verify --enable-plugin > > --with-system-zlib --with-target-system-zlib=auto > > --enable-objc-gc=auto --enable-multiarch --disable-werror > > --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 > > --enable-multilib --with-tune=generic > > --enable-offload-targets=nvptx-none,hsa --without-cuda-driver > > --enable-checking=release --build=x86_64-linux-gnu > > --host=x86_64-linux-gnu --target=x86_64-linux-gnu > > Thread model: posix > > gcc version 9.3.0 (Ubuntu 9.3.0-10ubuntu2~16.04) > >
