title: What's the relative speed of floating point add vs. floating point multiply
body: <p>A decade or two ago, it was worthwhile to write numerical code to avoid using multiplies and divides and use addition and subtraction instead.  A good example is using <a href="http://mathworld.wolfram.com/ForwardDifference.html" rel="noreferrer">forward differences</a> to evaluate a polynomial curve instead of computing the polynomial directly. </p>
  
  <p>Is this still the case, or have modern computer architectures advanced to the point where *,/ are no longer many times slower than +,- ?</p>
  
  <p>To be specific, I'm interested in compiled C/C++ code running on modern typical x86 chips with extensive on-board floating point hardware, not a small micro trying to do FP in software.  I realize pipelining and other architectural enhancements preclude specific cycle counts, but I'd still like to get a useful intuition.  </p>