# Bad but Short Mathematica Programs

Posted 4 months ago
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 Here are two programs. One of them is worse than the other. Which one is it? Manipulate[FactorInteger[a], {a, 1, 100000000, 1}] Manipulate[factored[[a]], {a, 1, 100000000, 1}, Initialization :> (factored = Table[FactorInteger[a], {a, 1, 100000000}]),SynchronousInitialization -> False] Hypothetically, the second program will perform slightly faster than the first. Realistically, the second program takes a long time to initialize. The first is rather zippy anyways. We can thus say that the second program is worse than the first. The lesson here is to not make a lot of unnecessary calculations.What are some other examples of short, bad programs, and their superior replacements?
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Posted 4 months ago
 Not using "nested Dynamics": Manipulate[ ContourPlot[Sin[5 x] Cos[7 y], {x, y} \[Element] Rectangle[], Epilog -> {AbsolutePointSize@12, Point[t {1, 1}]} ], {t, 0, 1} ] vs Manipulate[ ContourPlot[Sin[5 x] Cos[7 y], {x, y} \[Element] Rectangle[], Epilog -> {AbsolutePointSize@12, Point[Dynamic[t] {1, 1}]} ], {t, 0, 1} ] The second one is much smoother because the FrontEnd does not need to care about anything but t, when for the first case the whole ContourPlot is recalculated.