C# Exception Optimization

This C# optimization article tests the performance of exceptions. It uses code motion to improve exception handling speed.
Exception handling can be made faster. If you have an exception handling construct (try-catch) in an inner loop, you could hoist it to the outside of the loop. We demonstrate this code motion. We also provide benchmarks.
Example. This program introduces two methods we benchmark: Method1 and Method2. These methods are semantically different in only one way—if an exception is thrown, the entire loop terminates in Method2 but not in Method1.

Note: The try-catch block is inside the inner loop in Method1, and outside the loop in Method2.

C# program that optimizes exception construct using System; using System.Diagnostics; class Program { const int _max = 1000000; static void Main() { var s1 = Stopwatch.StartNew(); for (int i = 0; i < _max; i++) { Method1(); } s1.Stop(); var s2 = Stopwatch.StartNew(); for (int i = 0; i < _max; i++) { Method2(); } s2.Stop(); Console.WriteLine(((double)(s1.Elapsed.TotalMilliseconds * 1000 * 1000) / _max).ToString("0.00 ns")); Console.WriteLine(((double)(s2.Elapsed.TotalMilliseconds * 1000 * 1000) / _max).ToString("0.00 ns")); Console.Read(); } static void Method1() { for (int i = 0; i < 1000; i++) { try { int value = i * 100; if (value == -1) { throw new Exception(); } } catch { } } } static void Method2() { try { for (int i = 0; i < 1000; i++) { int value = i * 100; if (value == -1) { throw new Exception(); } } } catch { } } } Output 2555.43 ns: Method1 674.29 ns: Method2
Because no exceptions are thrown, the catch blocks are never reached. Method2, which has the try-catch outside the loop, is faster than Method1. If it doesn't affect runtime, hoisting exception handling outside a hot loop helps.TryCatch
Summary. Exception handling is relatively slow even if no exceptions are thrown. Code motion, which is a subset of optimization that includes hoisting expressions outside of loops, yields a performance gain.

However: There is a notable difference in the program semantics. The drawbacks must be weighed against the benefits.

© 2007-2019 Sam Allen. Every person is special and unique. Send bug reports to info@dotnetperls.com.
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