Re: Fast integer arithmetic
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- Subject: Re: Fast integer arithmetic
- From: Enrico Colombini <erix@...>
- Date: 2008年2月20日 14:34:35 +0100
John D. Ramsdell wrote:
A compile option to produce Lua binaries without
floating point instructions would create this faster version of Lua.
I just put this at the end of luaconf.h. It may not be perfect, but it
works (some of the redefinitions are identical to the originals, I put
them in for clarity).
Re-reading it, I'm not sure about LUAI_MAXNUMBER2STR. Should I count the
terminator? I'll have to check.
Enrico
-----------------------------------------------------------------
/*
* Notes:
* - pow() still uses double and is therefore slow
* - string.format('%f') converts to double with decimal part = 0
*/
/* this line switches LUA_NUMBER from double to int */
#define LUA_NUMBER_INT
/* patch starts here */
#ifdef LUA_NUMBER_INT
#undef LUA_NUMBER_DOUBLE
#undef LUA_NUMBER
#define LUA_NUMBER int
#undef LUAI_UACNUMBER
#define LUAI_UACNUMBER int
#undef LUA_NUMBER_SCAN
#undef LUA_NUMBER_FMT
#undef LUAI_MAXNUMBER2STR
#undef lua_str2number
#define LUA_NUMBER_SCAN "%d"
#define LUA_NUMBER_FMT "%d"
#define LUAI_MAXNUMBER2STR 12 /* 10 digits, sign, point, and 0円 */
#define lua_str2number(s,p) strtol((s), (p), 10)
#undef luai_nummod
#undef luai_numpow
#define luai_nummod(a,b) ((a) % (b))
#define luai_numpow(a,b) (int)(pow((double)a,(double)b) + 0.5)
#undef lua_number2int
#undef lua_number2integer
#define lua_number2int(i,d) ((i)=(int)(d))
#define lua_number2integer(i,d) ((i)=(lua_Integer)(d))
#endif /*LUA_NUMBER_INT*/
/* patch ends here */