Results

The results of optimising the evaluation of the Van Der Waal's forces are shown in table [].

Table: Timing comparison of different runs with Bak on XT4, XE6 and optimised vdw_forces on XE6

Nb. Procs	Bak XT4	Bak XE6	Opt vdw
16	199.154	218.722	212.913
32	106.790	98.113	94.590
64	63.129	57.494	56.761
128	42.036	39.360	35.121
256	27.471	29.492	25.631
512	22.137	25.951	21.641

The optimised version of vdw_forces shows a speed up of in average over all runs.A peak is observed at speed up compare to the Bak version on XE6 for 512 processes run.

Table: Variation rate of different runs of optimised vdw_forces on XE6 with Bak on XT4 and XE6

<#1177#>	Opt vdw comp. to
		Bak XT4	Bak XE6
16	6.91	-2.66
32	-11.42	-3.59
64	-10.09	-1.27
128	-16.45	-10.77
256	-6.7	-13.09
512	-2.24	-16.61
Average	-6.67	-8.00