id,summary,reporter,owner,description,type,status,milestone,component,version,severity,resolution,keywords,cc
5158,speed up lowest_bit() for gcc 4.x compatibles,astukalov@…,"James E. King, III","The patch provides specialization of lowest_bit() template that utilizes  __builtin_ctz[l][l]() function, available for gcc 4.x-compatible compilers, instead of calculation-intensive path that makes use of integer_log2().

Since lowest_bit() is used in dynamic_bitset::find_first()/find_next(), the patch leads to significant speed up for bitset traversal.

The patch was tested on gcc 4.5.2 x86_64 and icc 11.1 x86_64.

Currently, the patch provides no checks, if __builting_ctz is available for current toolset. I can try to add this, given the overall positive feedback.
",Feature Requests,new,,dynamic_bitset,,Optimization,,,