Test Case 4

The system simulated is PbO with 24 k-points. This simulation involves Hartee-Fock exchange calculations. Optical properties are also examined.

Table: Scaling of Test Case 4.

Test Case 6	Cores	Time (secs)	Speedup
VASP 5.2.2	256	14674.49	1
KPAR=2	512	7578.614	1.936
KPAR=3	768	4979.435	2.947
KPAR=4	1024	3790.061	3.871
KPAR=6	1536	2552.615	5.749
KPAR=8	2048	1944.401	7.548
KPAR=12	3072	1399.796	10.953
KPAR=24	6144	1053.134	13.93411

The original code failed to run on 512 cores or more. Hence the only way to run efficiently this problem is to employ the k-point parallelized version. This runs efficiently for this test case on up to 3072 cores.

Figure 4: Speedup of Test Case 4 (where Speedup is taken to be 1 for 256 cores.)