Re: [OMPI users] Can't compile C++ program with extern "C" { #include mpi.h }
On Mon, 2007-12-31 at 20:01 -0700, Brian Barrett wrote:
> On Dec 31, 2007, at 7:26 PM, Adam C Powell IV wrote:
>
> > Okay, fair enough for this test example.
> >
> > But the Salomé case is more complicated:
> > extern "C"
> > {
> > #include
> > }
> > What to do here? The hdf5 prototypes must be in an extern "C" block,
> > but hdf5.h #includes a file which #includes mpi.h...
> >
> > Thanks for the quick reply!
>
> Yeah, this is a complicated example, mostly because HDF5 should
> really be covering this problem for you. I think your only option at
> that point would be to use the #define to not include the C++ code.
>
> The problem is that the MPI standard *requires* mpi.h to include both
> the C and C++ interface declarations if you're using C++. There's no
> way for the preprocessor to determine whether there's a currently
> active extern "C" block, so there's really not much we can do. Best
> hope would be to get the HDF5 guys to properly protect their code
> from C++...
Okay. So in HDF5, since they call MPI from C, they're just using the C
interface, right? So should they define OMPI_SKIP_MPICXX just in case
they're #included by C++ and using OpenMPI, or is there a more MPI
implementation-agnostic way to do it?
Thanks again and happy new year!
-Adam
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[OMPI users] Tracing the library using gdb and xterm
Hi, I have been tracing the interactions between the PERUSE and MPI library,on one machine. I have been using gdb along with xterm to have two windows open at the same time as I step through the code. I wish to get a better glimpse of the working of the point to point calls, by launching the job on two machines and by tracing the flow in a similar manner. This is where I stand as of now : mpirun --prefix /usr/local -hostfile machines -np 2 xterm -e gdb peruse_ex1 xterm Xt error: Can't open display: xterm: DISPLAY is not set I tried using the display option for xterm and setting the value as 0.0, that was not of much help. If someone can guide me as to where the DISPLAY parameter has to be set to allow the remote machine to open the xterm window, it will be of great help. Thanks, Krishna -- In the middle of difficulty, lies opportunity
Re: [OMPI users] Tracing the library using gdb and xterm
Krishna, When you log in to the remote system, use ssh -X or ssh -Y which will export the xterm back thru the ssh connection. Jeff Pummill University of Arkansas Krishna Chaitanya wrote: Hi, I have been tracing the interactions between the PERUSE and MPI library,on one machine. I have been using gdb along with xterm to have two windows open at the same time as I step through the code. I wish to get a better glimpse of the working of the point to point calls, by launching the job on two machines and by tracing the flow in a similar manner. This is where I stand as of now : mpirun --prefix /usr/local -hostfile machines -np 2 xterm -e gdb peruse_ex1 xterm Xt error: Can't open display: xterm: DISPLAY is not set I tried using the display option for xterm and setting the value as 0.0, that was not of much help. If someone can guide me as to where the DISPLAY parameter has to be set to allow the remote machine to open the xterm window, it will be of great help. Thanks, Krishna -- In the middle of difficulty, lies opportunity ___ users mailing list us...@open-mpi.org http://www.open-mpi.org/mailman/listinfo.cgi/users
Re: [OMPI users] Can't compile C++ program with extern "C" { #include mpi.h }
On Jan 1, 2008, at 12:47 AM, Adam C Powell IV wrote: On Mon, 2007-12-31 at 20:01 -0700, Brian Barrett wrote: Yeah, this is a complicated example, mostly because HDF5 should really be covering this problem for you. I think your only option at that point would be to use the #define to not include the C++ code. The problem is that the MPI standard *requires* mpi.h to include both the C and C++ interface declarations if you're using C++. There's no way for the preprocessor to determine whether there's a currently active extern "C" block, so there's really not much we can do. Best hope would be to get the HDF5 guys to properly protect their code from C++... Okay. So in HDF5, since they call MPI from C, they're just using the C interface, right? So should they define OMPI_SKIP_MPICXX just in case they're #included by C++ and using OpenMPI, or is there a more MPI implementation-agnostic way to do it? No, they should definitely not be disabling the C++bindings inside HDF5 -- that would be a situation worse than the current one. Consider the case where an application uses both HDF5 and the C++ MPI bindings. It includes hdf5.h before mpi.h. The hdf5.h includes mpi.h, without the C++ bindings. The application then includes mpi.h, wanting the C++ bindings. But the multiple inclusion protection in mpi.h means nothing happens, so no C++ bindings. My comment about HDF5 was that it would be easiest if it protected its declarations with extern "C" when using C++. This is what most packages that might be used with C++ do, and it works pretty well. I'd actually be surprised if modern versions of HDF5 didn't already do that. Now that it's not New Years eve, I thought of what's probably the easiest solution for you. Just include mpi.h (outside your extern "C" block) before hdf5.h. The multiple inclusion protection in mpi.h will mean that the preprocessor removes everything from the mpi.h that's included from hdf5.h. So the extern "C" around the hdf5.h shouldn't be too much of a problem. Hope this helps, Brian -- Brian Barrett Open MPI developer http://www.open-mpi.org/
Re: [OMPI users] Tracing the library using gdb and xterm
Krishna, If you are using ssh to connect to the second machine you need to be sure that ssh X11 forwarding is enabled and you may need to have mpi use ssh -X or ssh -Y to connect to the second machine. That is how the DISPLAY gets set using ssh. Doug Reeder On Jan 1, 2008, at 8:11 AM, Krishna Chaitanya wrote: Hi, I have been tracing the interactions between the PERUSE and MPI library,on one machine. I have been using gdb along with xterm to have two windows open at the same time as I step through the code. I wish to get a better glimpse of the working of the point to point calls, by launching the job on two machines and by tracing the flow in a similar manner. This is where I stand as of now : mpirun --prefix /usr/local -hostfile machines -np 2 xterm -e gdb peruse_ex1 xterm Xt error: Can't open display: xterm: DISPLAY is not set I tried using the display option for xterm and setting the value as 0.0, that was not of much help. If someone can guide me as to where the DISPLAY parameter has to be set to allow the remote machine to open the xterm window, it will be of great help. Thanks, Krishna -- In the middle of difficulty, lies opportunity ___ users mailing list us...@open-mpi.org http://www.open-mpi.org/mailman/listinfo.cgi/users
