Amdahl’s Law

• Maximum expected improvement to an overall system when only part of the system is improved
• Theoretical maximum speedup using multiple processors
• $Speedup=\frac{\text{Execution time before improvement}}{\text{Execution time after improvement}}$
• $Speedup=((1-f_E)+(\frac{f_E}{f_I}){)}^{-1}$
  • $f_E$ is fraction enhanced
  • $f_I$ is factor of improvement
  • $S_e$ is speedup enhanced
• $ExecutionTim{e}_{new}=ExecutionTim{e}_{old}\times [(1-f_E)+f_E/S_e]$
• $MaximumSpeedupp=n/(1+(n-1)f)$
  • n is no of processors