Concurrency and program speed

[Joseph Rushton Wakeling]

On 02/28/2013 03:15 PM, Joseph Rushton Wakeling wrote:
> The times reported here are for programs compiled with GDC, but using LDC or DMD
> produces similar behaviour.

Come to that, so does a C example put together using pthreads -- just in case 
anyone thought I was holding D responsible.  But I'm somewhat curious as to why.

More general question: when using spawn(), is there a means to control the 
maximum number of simultaneous threads, other than not spawning them?  Something 
akin to std.parallelism's totalCPUs.