Re: [Libmesh-users] Fwd: further data Re: weird problem

[Roy S. <roy...@ic...>]

On Wed, 27 Jan 2010, Yujie wrote:

> In "dbg", the problem is always there.

I hadn't noticed before that you were running in debug mode.  Bad
performance is inherent to METHOD=dbg; we turn off optimization, we
test every assertion, we sometimes even add extra "double-checking"
libMesh code, GNU libstdc++ turns every std::vector index into a
checked index... worst of all, the GNU libstdc++ debug mode checks on
std::set actually have asymptotically greater cost than the operations
they're checking!

Performance with METHOD=dbg will always be lousy.  The solution is,
when you need performance, compile with METHOD=opt.
---
Roy