Xiao Liu PhD Thesis.pdf - Faculty of Information and Communication ...

segment is read in to increase the size of local workflow segment and the input
information is updated accordingly (Line 7 to Line 8). Afterwards, as the iteration
process carries on, ACOWR will optimise additional workflow segments until the
time deficit is entirely removed. In practice, according to our experimental results as
will be demonstrated in Section 8.6, two consecutive workflow segments are usually
more than enough to compensate the occurred time deficits for recoverable temporal
violations. Therefore, ACOWR will normally be applied no more than twice in the
PTDA+ACOWR strategy for handling level III temporal violations. Finally, the
optimised integrated Task-Resource list will be returned and deployed (Line 9).
8.5 Comparison of GA and ACO based Workflow Rescheduling
Strategies
8.5.1 Experimental Settings
In this section, comprehensive simulation and comparison experiments are
conducted to evaluate GA and ACO based workflow rescheduling strategies from
four important perspectives, including: the optimisation rates for the makespan; the
optimisation rates for the cost; the time deficit compensation rates; and the CPU
time of itself. All the program code as well as the experimental results can be found
online 9 .
A: Settings for Workflows
The basic experiment settings are presented in Table 8.1. Similar to the one
shown in Figure 8.2, workflow processes in the integrated Task-Resource list are
randomly generated as DAG task graphs with a random size of 3 to 5 activities. The
mean duration of each task is randomly selected from 30 to 3,000 basic time units
and its standard deviation is defined as 33% of its mean (a large standard deviation
for valid normal distribution models where the samples are all positive numbers
according to the “3 σ ” rule) to represent the highly dynamic performance of
underlying resources. Each resource contains three attributes including resource ID,
the execution speed and the execution cost. Here, the execution speed is defined as
9 http://www.ict.swin.edu.au/personal/xliu/doc/HandlingFramework.rar
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