From 72b3fff72f6bb9cf5796bbcd50e9a490d4e02b4b Mon Sep 17 00:00:00 2001 From: Mike Pall Date: Sun, 23 Jan 2011 14:23:21 +0100 Subject: FFI: Simplify initializer rules. Clarify docs. --- doc/ext_ffi.html | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) (limited to 'doc/ext_ffi.html') diff --git a/doc/ext_ffi.html b/doc/ext_ffi.html index e8e2a62b..f496b51b 100644 --- a/doc/ext_ffi.html +++ b/doc/ext_ffi.html @@ -73,8 +73,8 @@ The FFI library is tightly integrated into LuaJIT (it's not available as a separate module). The code generated by the JIT-compiler for accesses to C data structures from Lua code is on par with the code a C compiler would generate. Calls to C functions can -be inlined in the JIT-compiled code, unlike calls to functions bound -via the classic Lua/C API. +be inlined in JIT-compiled code, unlike calls to functions bound via +the classic Lua/C API.

This page gives a short introduction to the usage of the FFI library. @@ -253,14 +253,17 @@ would consume 40 Megabytes in plain Lua (on x64). Next, performance: the pure Lua version runs in 9.57 seconds (52.9 seconds with the Lua interpreter) and the FFI version runs in 0.48 seconds on my machine (YMMV). That's a factor of 20x faster (110x -faster than with plain Lua). +faster than the Lua interpreter).

The avid reader may notice that converting the pure Lua version over to use array indexes for the colors ([1] instead of .red, [2] instead of .green etc.) ought to be more compact and faster. This is certainly true (by a factor of -~1.7x), but the resulting code would be less idiomatic and rather +~1.7x). Switching to a struct-of-arrays would help, too. +

+

+However the resulting code would be less idiomatic and rather error-prone. And it still doesn't get even close to the performance of the FFI version of the code. Also, high-level data structures cannot be easily passed to other C functions, especially I/O functions, -- cgit v1.2.3-55-g6feb