reduce compilation times?

[Tim Prince]

John Love-Jensen wrote:
> Hi mahmoodn,
> 
>> I mean (I think):
>> "Allow N jobs at once"   !=    "reduce compile time"
> 
> Reduces my project's overall compile time on my machine, by a factor of 4.
> 
Might do that on a quad core. A dual core with HyperThreading enabled
approaches a factor of 3.  OP wants magic without qualification as to
platform.
Selective optimizations also are important; use -O3 only where it is useful.