Graphical representation of scalability

OS and hardware description

Myricom's private Opteron cluster, dual processor (single core) AMD Opteron 248, 2.2 GHz, TYAN S2891 baseboard with nVidia nForce Professional 2200 chipset, 4 GB DDR 333 RAM, 16 nodes, interconnect: Myri-10G network card with CX4 port (10G-PCIE-8A-C), Myri-10G switch, MX-10G version 1.2.0i (Myrinet Express), MPICH-MX 1.2.7.4 using MX_RCACHE=1 flag, Linux 2.6.17.11 (Ubuntu)

Test 1, single-point direct DFT (B3LYP) energy plus gradient for medium-size system (623 basis functions). View image

Test 3, single-point direct MP2 energy for medium-size system (623 basis functions, the same system as one used for Test 1). View image

Test 5, single-point direct CASSCF(12,12) for medium-size system (retinal molecule, cc-pVDZ, 565 Cartesian basis functions) using ALDET code. View image

Test 6, single-point direct CIS energy plus gradient of first excited state of medium-size system (porphyrin molecule, cc-pVTZ (aug-cc on Nitrogens), 1130 Cartesian basis functions, D_2h group). View image

All tests were run in standard parallel mode using dynamic load balancing over p2p interface, with two processes per each dual-CPU node. Wall clock times are given on master node in seconds. Test 5 is the most communication intensive and would scale better for larger job. For these tests, the most commonly used MPI calls are MPI_Allreduce and MPI_Bcast.