On Saturday, January 18, 2003, at 07:36 PM, Daniel Yerushalmi wrote:
<SNIP>A Cray is optimized for peak-floating point performance even for out-of-cache codes and optimized for that and not for compile time. There are several reasons why it is slow:
I'll try to do it at least once to see which parts of boost we can use,
and see how much CPU time this gobbles up. If it is not too much, I
will talk to our sysadmins if they would allow me to do it about once a
month. I don't think that testing more often would be possible, since
already compiling only the filesystem library takes about 15 minutes.
</SNIP>
?
How come? on my lowly PC it take less then a minute... (compiling just the
filesystem)
/Daniel Yerushalmy
i) in order to optimize the runtime performance the machine does not use virtual memory for a process, which makes dynamic allocation very slow. If I need more memory than was allocated initially, the whole process is swapped out and has to wait for a later time slice when more memory can be allocated. This is common when compiling template-heavy code.
ii) the fast vector units do not help anything for compiling the code.
iii) the optimizer is very aggressive, checking every piece of code for vectorization and parallelization possibilities, which makes it even slower. I don't think your PC compiler does that.
And finally, it actually only takes about 10 minutes to compile :)
Matthias
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