I'd like to be able to use MPI_Datatypes to send e.g. 4 GiB messages. Right now, even 2 GiB fails. Code is here https://github.com/jeffhammond/HPCGloves/tree/master/examples/mpi64. Test machine is in MCS. Thanks, Jeff [jhammond@protos mpi64]$ ./test_type_contig.x 15 count = 32768 ocount = 32768 [jhammond@protos mpi64]$ ./test_type_contig.x 20 count = 1048576 ocount = 1048576 [jhammond@protos mpi64]$ ./test_type_contig.x 25 count = 33554432 ocount = 33554432 [jhammond@protos mpi64]$ ./test_type_contig.x 30 count = 1073741824 ocount = 1073741824 [jhammond@protos mpi64]$ ./test_type_contig.x 31 count = 2147483648 Assertion failed in file ../src/mpid/common/datatype/dataloop/segment_packunpack.c at line 133: FALSE memcpy argument memory ranges overlap, dst_=0x254b310 src_=0x7f6ad81f3010 len_=-2147483648 internal ABORT - process 0 [jhammond@protos mpi64]$ ./test_type_contig.x 32 count = 4294967296 ocount = 0 -- Jeff Hammond Argonne Leadership Computing Facility University of Chicago Computation Institute [email protected] / (630) 252-5381 http://www.linkedin.com/in/jeffhammond https://wiki.alcf.anl.gov/parts/index.php/User:Jhammond ALCF docs: http://www.alcf.anl.gov/user-guides