Automap & Autolink : Tools for Communicating Complex and Dynamic Data-structures Using Mpi Automap : Generating New Mpi Types out of Data Structures 1 Data-types 1.2 Dynamic Data-type

More and more applications, business or scientiic, require intensive and complex processing of data along with computing power. Yet the development of real distributed applications has been hindered so far by programming diiculties. The Message Passing Interface standard (MPI) for message passing programs makes development easier through its portability and its high level language facilities (in C and Fortran). However, the MPI Standard functions support complex data types only indirectly. Users may create new MPI data-types out of basic data data-types for use with MPI functions but the process is tedious. Hence our idea to create high level tools that would enable the user to automatically create MPI data-types from user-deened C structures, and which enable the user to send and receive complex and dynamic data structures easily. Our tools consist of a program called AutoMap and a library called AutoLink. AutoMap parses a le of user-deened data-structures and generates new MPI types out of basic and previously deened MPI data-types. It also creates speciic routines for use by the AutoLink library. AutoLink is a library that allows transfer of complex, dynamically linked, and possibly heterogeneous structures through MPI. Outline The remainder of the paper is organized as follows. In the rst part we present AutoMap, and explain complex and dynamic data-types. We show how to create an MPI data-type from a user type, acknowledging that AutoMap does it automatically , as shown. Then, as we know what a dynamic data-structure is, we will see how AutoLink handles it to send such data. Finally, we will discuss performance, and then applications. The MPI library MPI94, MPI97] can only transfer types that it knows about. The C implementation of MPI knows about the basic types in C. Complex data-types (i.e. struct) can only be sent and received if they are described to the MPI library. AutoMap performs this service for the programmer. 1.1 Complex data-type In the C language, there are basic data-types such as int, char, long, double (.. .), for which an MPI type exists, like MPI_INT, MPI_CHAR, MPI_LONG, MPI_DOUBLE (.. .). But the user may want to be able to use a composition of such data-types. In C, such a composition may be created using the struct operand. A complex data-type is such a user-deened structure, as long as the user doesn't use pointers to other structures or components inside the structure. So, an example of a complex …