How to determine a good partition plan to ensure CPU balance in JSR 352?

Question

JSR 352 - Packaged applications for the Java platform provide a parallelism function using partitions. Batch runtime can perform a step in different sections to speed things up. JSR 352 also introduces a definition threads: we can determine the number of threads used, for example

<step id="Step1">
    <chunk .../>
        <partition>
            <plan partitions="3" threads="2"/>
        </partition>
    </chunk>
</step>

Then I feel embarrassed: how do I give an estimated partition plan so that each thread is busy and ensures CPU balance?

For example, there is a table A, B, C, and their rows are respectively 1 billion, 1 million, 1 thousand. The goal is to process these objects in documents, one organization moved to one document. The procedure for producing documents is not important. The CPU time for these objects is 1 s, 2 s, 5 s, respectively. The number of threads is 4.

If there are 3 sections, one for the table type, then the step will take 1 * 10^9seconds, because:

• Section A will take 1 * 10^9 * 1s = 1 * 10^9s, run in thread 2
• Section B will take 1 * 10^6 * 2s = 2 * 10^6s, start in thread 3
• Section C will take 1 * 10^3 * 5s = 5 * 10^3s, run in stream 4

However, although thread 2 is busy, thread 3 is free, since 2 * 10^6sthread 4 is free as well 5 * 10^3s. Obviously, this is not a good partition plan.

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