IWR6843ISK: What does cmn_DIVDP do?

Hi,

In my understanding, "cmn_DIVDP"(in mathlib_c674_3_1_2_1/packages/ti/mathlib/src/common/c674/common.h)  divides a by b.

So, what is the defference between "cmn_DIVDP(a, b)" and "a / b"? 

#define cmn_DIVDP(a,b) {  \
  double  TWO = 2.0;      \
  double  X;              \
  X = _rcpdp((b));        \
  X = X*(TWO - (b)*X);    \
  X = X*(TWO - (b)*X);    \
  X = X*(TWO - (b)*X);    \
  X = (a)*X;              \
  return (X);             \
}

Best regards.