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    <h2>Test Results</h2> <p>10,000,000 iterations of <strong>Block 1</strong></p> <pre><code>myFlag = 0: 23.8ns per iteration myFlag = 1: 23.8ns per iteration </code></pre> <p>10,000,000 iterations of <strong>Block 2</strong></p> <pre><code>myFlag = 0: 23.8ns per iteration myFlag = 1: 46.8ns per iteration </code></pre> <p><strong>Block 2</strong> is 96% slower than <strong>Block 1</strong>. Makes sense, since <strong>Block 2</strong> does twice the work in the pessimistic case.</p> <blockquote> <p>i prefer either case, depending on the situation. If <code>myFlag</code> is <em>rarely ever</em> 1, then it want it to stand out as the edge case that we have to handle. If both are equally likely, i want the <code>if-else</code> syntax. But that's preference, not fact.</p> </blockquote> <hr> <p>Decades ago, the intel 80286 dual pipeline would stall if a conditional jump was taken, rather than falling through to the next instruction. By the time of the Pentium that went away; the CPU pre-fetches both branch paths. But in the back of my mind i still have a twinge of fear whenever i write code that has the most common outcome in the <code>else</code> clause. Every time i have to remind myself that it doesn't matter anymore.</p> <hr> <pre><code>Int32 reps = 10000000; private void Block1(int myFlag) { String width; String height; Stopwatch sw = new Stopwatch(); sw.Start(); for (int i = 0; i &lt; reps; i++) { if (myFlag == 1) { width = String.Format("{0:g}%", 60); height = String.Format("{0:g}%", 60); } else { width = String.Format("{0:g}%", 80); height = String.Format("{0:g}%", 80); } } sw.Stop(); Double time = (Double)sw.Elapsed.Ticks / Stopwatch.Frequency * 1000000000.0 / reps; MessageBox.Show(time.ToString() + " ns"); } private void Block2(int myFlag) { String width; String height; Stopwatch sw = new Stopwatch(); sw.Start(); for (int i = 0; i &lt; reps; i++) { width = String.Format("{0:g}%", 80); height = String.Format("{0:g}%", 80); if (myFlag == 1) { width = String.Format("{0:g}%", 60); height = String.Format("{0:g}%", 60); } } sw.Stop(); Double time = (Double)sw.Elapsed.Ticks / Stopwatch.Frequency * 1000000000.0 / reps; MessageBox.Show(time.ToString() + " ns"); } </code></pre> <ul> <li><code>String.Format</code> makes <code>IF</code> 96% slower</li> <li><code>GetPercentageString(0.60)</code> makes <code>IF</code> 96% slower</li> </ul> <hr> <pre><code>const reps = 10000000; procedure Block1(myflag: Integer); var width, height: string; i: Integer; t1, t2: Int64; time: Extended; freq: Int64; begin QueryPerformanceCounter(t1); for i := 1 to reps do begin if myFlag = 1 then begin width := '60%'; height := '60%'; end else begin width := '80%'; height := '80%'; end; end; QueryPerformanceCounter(t2); QueryPerformanceFrequency(freq); time := (t2-t1) / freq * 1000000000 / reps; ShowMessage(FloatToStr(time)+ 'ns'); end; procedure Block2(myflag: Integer); var width, height: string; i: Integer; t1, t2: Int64; time: Extended; freq: Int64; begin QueryPerformanceCounter(t1); for i := 1 to reps do begin width := '80%'; height := '80%'; if myFlag = 1 then begin width := '60%'; height := '60%'; end; end; QueryPerformanceCounter(t2); QueryPerformanceFrequency(freq); time := (t2-t1) / freq * 1000000000 / reps; ShowMessage(FloatToStr(time)+ 'ns'); end; </code></pre> <hr> <p>Doing twice the amount of work takes roughly twice the amount of time.</p> <p>Answer: IF does not perform better than IF-ELSE.</p> <hr> <p><img src="https://i.stack.imgur.com/CCQRH.png" alt="enter image description here"></p>
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    1. USIan Boyd
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    1. CO+1 for considering the burden of 1 extra assignment. Though we have advanced cpus, but we dont have them always everywhere. There are processors still running at 20MHz and everything makes sense there.
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      1. USAbhinav
    2. CO@abhinav: 20MHz is still **20 MILLION** operations per second. Even in that case, this is a pre-optimization, so unless this is a *known* performance bottleneck, it's not worth the time it takes to think about it.
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    3. CODon't bother to save battery power on my handheld when you don't have it. It's a free optimization that costs nothing to do. Granted, it would be useful if the compiler optimized the identical code blocks to the better case.
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