Re: [boost] [uuid] uuid::create() is extremely slow

From: Peter Dimov (pdimov_at_[hidden])
Date: 2007-06-01 14:24:40

Dave Jenkins wrote:
> Andy,
> You did a nice job speeding up the uuid::create(engine) function to
> 0.4 seconds for 1 million UUIDs.  But now the uuid::create() function
> is extremely slow - 131 seconds for 1 million UUIDs (source code
> below).

The requirement for uuid::create to be fast conflicts with the requirement 
that it needs to create a "universally unique identifier", that is, a 
high-quality random number. Typically, high-quality randomness is more 
important than performance, as one rarely needs to create one million UUIDs. 
One could argue that the high-performance case is adequately addressed by 
the engine-taking overload.

> Can you change it to use a static mt19937 engine?

This introduces thread safety issues.

All that said, the current uuid::create throws away most of the randomness 
produced by the random digest helper function and uses only 32 bits of it as 
a seed, so it's not really high quality. :-)