Altera opencl, Diff usage of Processors when using parallel compilation of Quartus.

I am using "Hello world" of example designs offered by Altera Opencl. (https://www.altera.com/products/desi...esign-examples)

I use the "aoc" command and get the .aocx file.

but I have a confusion:

in the file "top.sta.rpt", it have something like this:

• +------------------------------------------+
• ; Parallel Compilation ;
• +----------------------------+-------------+
• ; Processors ; Number ;
• +----------------------------+-------------+
• ; Number detected on machine ; 8 ;
• ; Maximum allowed ; 4 ;
• ; ; ;
• ; Average used ; 1.08 ;
• ; Maximum used ; 4 ;
• ; ; ;
• ; Usage by Processor ; % Time Used ;
• ; Processor 1 ; 100.0% ;
• ; Processors 2-3 ; 2.9% ;
• ; Processor 4 ; 2.2% ;
• +----------------------------+-------------+

Problem:
1. Why Processor 1 is using 100%, and other Processor only use nearly 3% ?
2. How can I increase the usage of Processor 2-4 ?

Thank you, wait for your apply~