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h2. Purpose of the Experiment
The workflow presented above is embedded in a new workflow in order to generate a test series. A list of 40 values, ranging from 10 to 400 in steps of 10 files to be processed per invocation is given as input to the “num_files_per_invocation” parameter. [Taverna|http://www.taverna.org.uk/] will then automatically iterate over the list of input values by combining the input values as a cross product and launching 40 workflow runs for the embedded workflow.
5 ARC container files with a total size of 481 Megabytes and 42223 individual files were used as input for this experiment. The 40 workflow cycles were completed in around 24 hours and led to the result shown in figure 3. !execution_time_vs_number_of_files_per_invokation.png|border=1,width=503,height=253!
_Figure 3: Execution time vs. number of files processed per invocation._
The experiment shows a range of values with the execution time stabilising at about 30 minutes. Additionally, the evolution of the execution time of the average and worst performing task is illustrated in figure 4 and can be taken into consideration to choose the right parameter value. !average_and_worst_performing_tasks.png|border=1!
_Figure 4: Average and worst performing tasks._
Based on this preparatory experiment, the parameter to set the number of lines per ToMaR invocation was set to 250.