Dear Gilles et al,
You are correct. I solved the problem based on an email I got
privately based on the same idea. I have just posted that private
reply so the solution will be more widely known among us amateurs.
Thanks,
George Reeke
On Tue, 2017-01-31 at 09:07 +0900, Gilles Gouaillardet wrote:
> George,
>
>
> at first glance, it seems GHtyp is initialized too early with
>
> uninitialized types MPHdr and MPBlk.
>
>
> can you try to initialize GHtyp *after* both types are commited ?
>
>
> if it still does not work, could you please post a self contained and
> simple reproducer ?
>
>
> Cheers,
>
>
> Gilles
>
>
> On 1/31/2017 6:31 AM, George Reeke wrote:
> > Dear colleagues,
> > I am trying MPI_Type_create_struct for the first time.
> > I want to combine a small structure (two ints) with a vector of
> > variable length to send in a single message. Here is a simplified
> > extract of the relevant C code. The MPI_Type_create_struct call
> > gives a segfault. The nearest I can see to what is wrong is that
> > the argument I called GHtyp has as its first element a small
> > integer (0x53) which the function ompi_datatype_create_struct
> > is trying to use as a pointer. But I thought I created it with
> > an MPI_Type_contiguous call:
> >
> > /* The next three variables are passed in from other
> > * calculations and have reasonable values per gdb. */
> > char *pv = /* Pointer to my data array */
> > int lblk = /* Length of one element of my data array */
> > int nblks = /* Number of these blocks in the data vector */
> > MPI_Datatype MPHdr,MPBlk,MPPkt;
> > struct GHdr_t {
> > int odat, nblk; /* Code to set these values not shown */
> > } sGHdr;
> > int GHect[2] = { 1, 0 }; /* Second count inserted below */
> > MPI_Datatype GHtyp[2] = { MPHdr, MPBlk };
> > MPI_Aint GHoff[2];
> > /* Executable code */
> > MPI_Type_contiguous(2, MPI_UNSIGNED, &MPHdr);
> > MPI_Type_commit(&MPHdr);
> > MPI_Type_contiguous(lblk, MPI_UNSIGNED_CHAR, &MPBlk);
> > MPI_Type_commit(&MPBlk);
> > GHect[1] = nblks;
> > MPI_Get_address(pv, GHoff+1);
> > MPI_Get_address(&sGHdr, GHoff);
> > MPI_Type_create_struct(2, GHect, GHoff, GHtyp, &MPPkt);
> > ----segfault on this call-never gets to the following commit----
> >
> > Any suggestions would be most welcome.
> > Thanks,
> > George Reeke
> >
> >
> >
> >
> >
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