More threads -> Slower program ??

[Adam D. Ruppe via Digitalmars-d-learn]

On Wednesday, 12 August 2015 at 23:06:32 UTC, Yuxuan Shui wrote:
> What is wrong here?

I didn't look too closely, but there's some memory allocations 
going on there which have the potential of locking all the 
threads any time one of them tries to allocate.

Parallelism's benefits are largely erased by the memory allocator 
lock and can be set back by the cache being invalidated as it 
jumps around that allocated memory, so you generally want to make 
sure the threads are doing work on local variables only.

This restricts what you can do with strings, since most the 
std.string functions allocate new strings for their return 
values...