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copied!<h1>Test case 1: <code>a</code> and <code>b</code> both global, no embedding.</h1> <pre><code>$ cat junk.lua ; time lua junk.lua function a(n) return n + 1 end function b(n) return a(n) end for c = 1, 10000000 do b(c) end real 0m1.743s user 0m1.740s sys 0m0.000s </code></pre> <p>User time: <strong>1.74s</strong>.</p> <h1>Test case 2: <code>a</code> local, <code>b</code> global, no embedding.</h1> <pre><code>local function a(n) return n + 1 end function b(n) return a(n) end for c = 1, 10000000 do b(c) end real 0m1.388s user 0m1.390s sys 0m0.000s </code></pre> <p>User time <strong>1.39s</strong>.</p> <h1>Test case 3: <code>a</code> and <code>b</code> both local, no embedding.</h1> <pre><code>$ cat junk.lua ; time lua junk.lua local function a(n) return n + 1 end local function b(n) return a(n) end for c = 1, 10000000 do b(c) end real 0m1.194s user 0m1.200s sys 0m0.000s </code></pre> <p>User time <strong>1.2s</strong>.</p> <h1>Test case 4: <code>a</code> embedded in <code>b</code>, <code>a</code> global, <code>b</code> local.</h1> <pre><code>$ cat junk.lua ; time lua junk.lua local function b(n) function a(n) return n + 1 end return a(n) end for c = 1, 10000000 do b(c) end real 0m2.804s user 0m2.790s sys 0m0.000s </code></pre> <p>User time: <strong>2.79s</strong>. (!)</p> <h1>Test case 5: <code>a</code> embedded in <code>b</code>, both local.</h1> <pre><code>$ cat junk.lua ; time lua junk.lua local function b(n) local function a(n) return n + 1 end return a(n) end for c = 1, 10000000 do b(c) end real 0m2.540s user 0m2.530s sys 0m0.000s </code></pre> <p>User time: <strong>2.53s</strong>.</p> <h1>Result summary:</h1> <ol> <li>It's easy to write tests to confirm or deny intuitions about performance. You should probably do this instead of relying on crowd-sourcing the answer. (The crowd is often wrong, you see.)</li> <li>Making functions local instead of global has a significant positive impact on function call overhead. (About 30% better in this set of test cases when both functions were local.)</li> <li>Embedding a function in another function has a serious negative impact on function call overhead. (About 110% worse in this set of test cases when both functions were local.)</li> <li>Did I mention that testing is probably a good idea in lieux of trusting the crowd?</li> </ol>

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