Vedran Coralic wrote: > Hello, > > In my Fortran 90 code I use several custom defined derived types. > Amongst them is a vector of arrays, i.e. v(:)%f(:,:,:). I am wondering > what the proper way of sending this data structure from one processor to > another is. Is the best way to just restructure the data by copying it > into a vector and sending that or is there a simpler way possible by > defining an MPI derived type that can handle it? > > I looked into the latter myself but so far, I have only found the > solution for a scalar fortran derived type and the methodology that was > suggested in that case did not seem naturally extensible to the vector case. >
It depends on how your data is distributed in memory. If the arrays are evenly distributed, like what would happen in a multidimensional-array, the derived datatypes will work fine. If you can't guarantee the spacing between the arrays that make up the vector, then using MPI_Pack/MPI_Unpack (or whatever the Fortran equivalents are) is the best way to go. I'm not an expert MPI programmer, but I wrote a small program earlier this year that created a dynamically created array of dynamically created arrays. After doing some research into this same problem, it looked like packing/unpacking was the only way to go. Using Pack/Unpack is easy, but there is a performance hit since the data needs to be copied into the packed buffer before sending, and then copied out of the buffer after the receive. -- Prentice
