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• Detect Shift Overflow

  This is an intellectual exercise: when shifts a 32-bit unsigned integer in C++, how to detect whether the calculation overflows efficiently? Here is the function prototype. shl_overflow will return true if v << cl overflows (cl is between 0 and Read More... Posted Saturday, June 13, 2009 6:19 AM by xiangfan | 0 Comments Filed under: C++, VC, Optimization

• Optimize Your Code: Matrix Multiplication

  Matrix multiplication is common and the algorithm is easy to implementation. Here is one example: Version 1: template < typename T> void SeqMatrixMult1( int size, T** m1, T** m2, T** result) { for ( int i = 0; i < size; i++) { for ( int j = 0; Read More... Posted Tuesday, April 28, 2009 1:30 PM by xiangfan | 1 Comments Filed under: C++, Optimization

• Magic behind ValueType.Equals

  In "Effective C#", Bill Wagner says "Always create an override of ValueType.Equals() whenever you create a value type". His main consideration is the performance, because reflection is needed to compare two value types memberwisely. In fact, the framework Read More... Posted Monday, September 01, 2008 4:35 PM by xiangfan | 1 Comments Filed under: Optimization, Bug, C#