float
/fp:strict
FLT_EVAL_METHOD
fp_contract
http://stackoverflow.com/questions/10713195/ieee-754-floating-point-computations-equality-and-narrowing
http://randomascii.wordpress.com/2012/03/21/intermediate-floating-point-precision/
http://stackoverflow.com/questions/6423547/fpprecise-vs-fpstrict-performance
http://stackoverflow.com/questions/12514516/difference-between-fpstrict-and-fpprecise
http://nyaruru.hatenablog.com/entries/2006/06/15