Performance and Complexity

Performance的三個要素是時間, 空間, 網路; Complexity是用來衡量Performance的指標

1. Performance

• Consuming more of one resource can help consume less of another

• Measure of performance

  • Time

    • The mount of processing or number of operations code has to perform to accomplish it's objective

  • Space

    • This is both memory needed by code to store information at runtime as well as disk space needed by code for persistent storage

  • Network

    • The bandwidth code uses to pass information to client or other machines

  • Efficient code uses fewer resource along all these axes

• The amount of resource used determines code's performance

2. Complexity

• Focus here is on space and time complexity

• Complexity is a measure of how resource requirement change as the size of the problem gets larger

  • 當input size 變大時, complexity很重要

  • We also focus on the worst case performance

  • What is the maximum number of basic operations that might have to be performed on the input

• The higher the complexity of a problem the lower the performance