From e075c846fff22c677a06cc94bd2326c1cf615714 Mon Sep 17 00:00:00 2001
From: Mitja Felicijan <mitja.felicijan@gmail.com>
Date: Fri, 11 Apr 2025 22:03:18 +0200
Subject: New note: Lua performance

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+---
+title: Lua performance in different environments
+url: lua-performance-in-different-environments.html
+date: 2025-04-11T16:13:13+02:00
+type: note
+draft: false
+tags: []
+---
+
+A quick look into difference in performance when running Lua normally vs Luajit
+vs Lua embedded in C program. 
+
+You can also check code on GitHub
+[@mitjafelicijan/probe/c-luajit](https://github.com/mitjafelicijan/probe/tree/master/c-luajit).
+
+Do not take this data as a benchmark, it's just a naive quick checkup.
+
+## Naive and intentionally slow implementation of Fibonacci sequence
+
+```lua
+-- Naive recursive implementation to increase the time of computation.
+function fibonacci(n)
+    if n == 0 then
+        return 0
+    elseif n == 1 then
+        return 1
+    else
+        return fibonacci(n - 1) + fibonacci(n - 2)
+    end
+end
+
+local n = 40
+local result = fibonacci(n)
+print("The " .. n .. "th Fibonacci number is: " .. result)
+```
+
+## Embedded Lua primer
+
+```sh
+#include <lua.h>
+#include <lualib.h>
+#include <lauxlib.h>
+
+int main(void) {
+    lua_State *L = luaL_newstate();
+    luaL_openlibs(L);
+
+    if (luaL_loadfile(L, "fibonacci.luac") || lua_pcall(L, 0, 0, 0)) {
+        fprintf(stderr, "Error: %s\n", lua_tostring(L, -1));
+        return 1;
+    }
+
+    lua_close(L);
+    return 0;
+}
+```
+
+## Quick results
+
+| Lua    | Luajit | Lua embedded in C |
+|--------|--------|-------------------|
+| 6.006s | 1.065s | 1.065s            |
+
+## Test script
+
+```sh
+#!/usr/bin/env bash
+
+ITERATIONS=120
+
+# Just Lua interpreter
+for i in $(seq 1 $ITERATIONS); do
+    echo "> lua run #$i/$ITERATIONS"
+    /usr/bin/time -f "%e,%U,%S" lua fibonacci.lua > /dev/null 2>> out.lua.txt
+done
+
+# Using Luajit
+for i in $(seq 1 $ITERATIONS); do
+    echo "> luajit run #$i/$ITERATIONS"
+    /usr/bin/time -f "%e,%U,%S" luajit fibonacci.lua > /dev/null 2>> out.luajit.txt
+done
+
+# With C and Luajit
+for i in $(seq 1 $ITERATIONS); do
+    echo "> cluajit run #$i/$ITERATIONS"
+    /usr/bin/time -f "%e,%U,%S" ./fibonacci > /dev/null 2>> out.cluajit.txt
+done
+```
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