vrda_exp: Array double precision exponential function

• C Prototype:
  • void vrda_exp (int n, double *x, double *y)

  • Inputs:

    • int	n	- the number of values in both the input and output arrays.
      double	*x	- pointer to the array of input values.
      double	*y	- pointer to the array of output values.

  • Outputs:
    • e raised to the power x (exponential of x) for each x value, filled into the y array.
• Fortran Subroutine Interface:
  • SUBROUTINE VRDA_EXP(N,X,Y)
  • Inputs:
    • INTEGER N - the number of values in both the input and output arrays.
    • DOUBLE PRECISION X(N) - array of double precision input values.
  • Outputs:
    • DOUBLE PRECISION Y(N) - array of exponentials (e raised to the power x) of input values.
• Notes:
  • vrda_exp computes the double precision exponential function for each element of an array of input arguments.
    This routine accepts an array of double precision input values, computes the e^x for each input value, and stores the result in the array pointed to by the y pointer input. It is the responsibility of the calling program to allocate/deallocate enough storage for the output array. This is a relaxed version of exp, suitable for use with fastmath compiler flags or applications not requiring full error handling. Denormal inputs may produce unpredictable results. Special case inputs produce C99 return values. The routine is accurate to better than 1 ulp over the valid input range.
• Special case return values:

  • Input	Output
    QNaN	same QNaN
    SNaN	same NaN converted to QNaN
    < -708.5	0
    > 709.8	+infinity

• Performance:
  • 33 cycles per value for valid inputs, n = 24.