Optimization: flags setting

From: Vladimir Prus (ghost_at_[hidden])
Date: 2004-12-17 08:44:33

Summary: the toolset.set-target-variables rule was pretty slow and is 
optimised a bit now.

Details: setting variables on targets includes two parts: deciding what flags 
are applicable and applying the flags. The first part requires checking 
property sets and is pretty slow. It's optimised by cacheing.

Compatibility: only Boost.Build update is needed

Performance: results on two testcases (each run 3 times) are below. Not very 
great change, but still significant.

Femtown (reference Boost.Build)
Real: min 39:600, max 44:420, avg 42:86
User: min 36:240, max 37:340, avg 36:833

Femtown (CVS Boost.Build)
Real: min 35:250, max 43:270, avg 39:370
User: min 32:360, max 34:60, avg 33:430

TBLib (reference Boost.Build)
Real: min 19:60, max 25:370, avg 22:730
User: min 17:150, max 19:70, avg 18:203

TBLib (CVS Boost.Build)
Real: min 16:450, max 19:230, avg 17:576
User: min 14:540, max 15:420, avg 14:903

- Volodya