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POBenchmarking: using `expression` `quote` or neither
 

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    <p>Generally, when I run benchmarks, I wrap my statements in <code>expression</code>. Recently, it was suggested to either (a) not do so or (b) use <code>quote</code> instead of expression. </p> <p>I find two advantages to wrapping the statements: </p> <ul> <li>compared to entire statements, they are more easily swapped out. </li> <li>I can lapply over a list of inputs, and compare those results</li> </ul> <p>However, in exploring the different methods, I noticed a discrepency between the three methods (wrapping in <code>expression</code>, wrapping in <code>quote</code>, or not wrapping at all) </p> <p><strong>The question is:</strong><br> Why the discrepency? <BR> (it appears that wrapping in <code>quote</code> does not actually evaluate the call.)</p> <h2>EXAMPLE:</h2> <pre><code># SAMPLE DATA mat &lt;- matrix(sample(seq(1e6), 4^2*1e4, T), ncol=400) # RAW EXPRESSION TO BENCHMARK IS: # apply(mat, 2, mean) # WRAPPED EXPRESSION: expr &lt;- expression(apply(mat, 2, mean)) quot &lt;- quote(apply(mat, 2, mean)) # BENCHMARKS benchmark(raw=apply(mat, 2, mean), expr, quot)[, -(7:8)] # test replications elapsed relative user.self sys.self # 2 expr 100 1.269 NA 1.256 0.019 # 3 quot 100 0.000 NA 0.001 0.000 # 1 raw 100 1.494 NA 1.286 0.021 # BENCHMARKED INDIVIDUALLY benchmark(raw=apply(mat, 2, mean))[, -(7:8)] benchmark(expr)[, -(7:8)] benchmark(quot)[, -(7:8)] # results # test replications elapsed relative user.self sys.self # 1 raw 100 1.274 1 1.26 0.018 # test replications elapsed relative user.self sys.self # 1 expr 100 1.476 1 1.342 0.021 # test replications elapsed relative user.self sys.self # 1 quot 100 0.006 1 0.006 0.001 </code></pre>
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