Good day, I'm studying the impact of MPI process binding on communication costs in my project, and would like to use hwloc-bind to achieve fine-grained mapping control. I install hwloc 1.1.1 on a 2-socket 4-core machine (with 2 dual-core dies in each socket), and run hwloc-ps to verify the binding: $ mpirun -Vmpirun (Open MPI) 1.5.1$ mpirun -np 4 hwloc-bind socket:0.core:0-3 ./test hwloc-ps shows the following output: $ hwloc-ps -p1497 Socket:0 ./test1498 Socket:0 ./test1499 Socket:0 ./test1500 Socket:0 ./test$ hwloc-ps -l1497 Socket:0 ./test1498 Socket:0 ./test1499 Socket:0 ./test1500 Socket:0 ./test$ hwloc-ps -c1497 0x00000055 ./test1498 0x00000055 ./test1499 0x00000055 ./test1500 0x00000055 ./test
Questions: 1. Does hwloc-bind map the processes *sequentially* on *successive* cores of the socket?2. How could hwloc-ps help verify this binding, i.e., process 1497 (rank 0) on socket.0:core.0process 1498 (rank 1) on socket.0:core.1process 1499 (rank 2) on socket.0:core.2process 1500 (rank 3) on socket.0:core.3 Equivalently, does the binding of `socket:0.core:0-1 socket:1.core:0-1' with hwloc-ps showing $ hwloc-ps -l1315 L2Cache:0 L2Cache:2 ./test1316 L2Cache:0 L2Cache:2 ./test1317 L2Cache:0 L2Cache:2 ./test1318 L2Cache:0 L2Cache:2 ./test indicate the the following? I.e., process 1315 (rank 0) on socket.0:core.0process 1316 (rank 1) on socket.0:core.1process 1317 (rank 2) on socket.1:core.0process 1318 (rank 3) on socket.1:core.1 The topology of the machine is as follows: $ hwloc-info -ldepth 0: 1 Machine (type #1) depth 1: 2 Sockets (type #3) depth 2: 4 Caches (type #4) depth 3: 8 Caches (type #4) depth 4: 8 Cores (type #5) depth 5: 8 PUs (type #6) $ lstopoMachine (16GB) Socket L#0 L2 L#0 (4096KB) L1 L#0 (32KB) + Core L#0 + PU L#0 (P#0) L1 L#1 (32KB) + Core L#1 + PU L#1 (P#2) L2 L#1 (4096KB) L1 L#2 (32KB) + Core L#2 + PU L#2 (P#4) L1 L#3 (32KB) + Core L#3 + PU L#3 (P#6) Socket L#1 L2 L#2 (4096KB) L1 L#4 (32KB) + Core L#4 + PU L#4 (P#1) L1 L#5 (32KB) + Core L#5 + PU L#5 (P#3) L2 L#3 (4096KB) L1 L#6 (32KB) + Core L#6 + PU L#6 (P#5) L1 L#7 (32KB) + Core L#7 + PU L#7 (P#7) Thanks.Chan ____________________________________________________________________________________ Never miss an email again! Yahoo! Toolbar alerts you the instant new Mail arrives. http://tools.search.yahoo.com/toolbar/features/mail/
