vrda_cos: Array double precision Cosine

• C Prototype:
  • void vrda_cos (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:
    • Cosine for each x value, filled into the y array.
• Fortran Subroutine Interface:
  • SUBROUTINE VRDA_COS(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 Cosines of input values.
• Notes:
  • vrda_cos computes the Cosine function for each element of an array of input arguments.
    This routine accepts an array of double precision input values, computes cos(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 cos, 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 2 ulp over the valid input range.
• Special case return values:

  • Input	Output
    QNaN	same QNaN
    SNaN	same NaN converted to QNaN
    +infinity	QNaN
    -infinity	QNaN

• Performance:
  • 172 cycles for most valid inputs < 5e5 (43 cycles per value), n = 24.