Vectors revisited

This code creates a datatype for an arbitrary number of element in a row of an array stored in Fortran order (column first).

int blens[2], displs[2]; 
MPI_Datatype types[2], rowtype; 
blens[0]  = 1; 
blens[1]  = 1; 
displs[0] = 0; 
displs[1] = number_in_column * sizeof(double); 
types[0]  = MPI_DOUBLE; 
types[1]  = MPI_UB; 
MPI_Type_struct( 2, blens, displs, types, &rowtype ); 
MPI_Type_commit( &rowtype ); 

MPI_Send( buf, n, rowtype, ... );