Log2 seems inefficient
KENNON J CONRAD via Cygwin <[email protected]>
| Newsgroups | gmane.os.cygwin |
|---|---|
| Message-ID | <[email protected]> |
Hello, I am not an experienced cygwin user but have been using it to compile code on Windows (gcc), so I may be leaving out some key details. My issue is that for every log2 call in my code there is a divide that follows a log library call in the assembly code. It appears to be related to these lines in math.h: #if !defined(__cplusplus) #define log2(x) (log (x) / _M_LN2) #endif My questions are: If log(x) is used, wouldn't it be faster to multiply by constant (1/LN2) instead of divide by constant (LN2)? And wouldn't it be even more efficient to compute log2 directly instead of computing the natural log and then converting it to log2? I realize this is not a "bug", it just doesn't seem very optimal from an speed standpoint. Best Regards, Kennon Conrad -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple