Hello, everybody who abstained or voted against the proposal, please read ticket #33 and discuss any open issue or question either here or with me. I would be happy to answer any questions or address any doubts. A new implementation for all versions of the proposed scalable graph interface is attached to ticket #33 (virtual_graph_scal.cpp) (https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/33). This version does not implement the new interface on top of the old interface and thus reduces the memory consumption per process from O(N*N) to O(N) (assuming a reasonable specification). The implementation is trivial (took me about 2 hours) and the most complex function has 76 lines of code. The whole proposal including an example has 199 lines of code (many of this are interface definitions). As discussed, the communication overhead for the adjacent interface is zero and the worst-case communication overhead for the general interface is O(N) per process, however, the expected case is O(1) (constant). The attached implementation now achieves all goals of ticket #33, it increases the scalability of the graph interface by reducing the memory on the user-side to a lower complexity class and the communication is optimized. Ths significance of improvement is shown in the following table which lists the maximum memory consumption in bytes for different communicator sizes with the old and the new interface (assuming 8 byte integers). processes MPI-2.1 interface proposed interface 512 2 MiB 2 kiB 1024 8 MiB 8 kiB 4096 134 MiB 32 kiB 16384 2.1 GiB 131 kiB 65536 34.4 GiB 524 kiB This is an upper bound, if you are interested in sparse graphs, multiply both numbers by 0.01 (1% sparsity). The relative scaling remains the same. All issues related to process remapping are not part of the ticket and are not touched (the main intent of this ticket is to enable the use of virtual graph topologies at scale at all). However, if you are interested in this matter, there is an extensive body of research in this area: "Rank Reordering Strategy for MPI Topology Creation Functions" http://www.springerlink.com/content/f3hqq5u2v14tpu53/ "Topology mapping for Blue Gene/L supercomputer" http://portal.acm.org/citation.cfm?id=1188576 "Implementing the MPI process topology mechanism" http://portal.acm.org/citation.cfm?id=762761.762767 "Scheduling regular and irregular communication patterns on the CM-5" http://portal.acm.org/citation.cfm?id=147877.148034 Thanks & All the Best, Torsten -- bash$ :(){ :|:&};: --------------------- http://www.unixer.de/ ----- Torsten Hoefler, Ph.D. | Postdoctoral Fellow Open Systems Lab | Indiana University 150 S. Woodlawn Ave. | Bloomington, IN, 474045, USA Lindley Hall Room 135 | +01 (812) 855-3608