fastsin: fast double precision Sine

• Weak alias: sin
• C Prototype:
  • double fastsin (double x);
  • Inputs:
    • double x - the double precision input value.
  • Outputs:
    • Sine of x.
• Fortran Function Interface:
  • DOUBLE PRECISION FASTSIN(X)
  • Inputs:
    • DOUBLE PRECISION X - the double precision input value.
  • Return Value:
    • Sine of X.
• Notes:
  • fastsin computes the Sine function of its argument x.
    
    This is a relaxed version of sin, suitable for use with fastmath compiler flags or applications not requiring full error handling. Denormal inputs may produce unpredictable results. Error 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
    +infinity	QNaN
    -infinity	QNaN

• Performance:
  • 88 cycles for most valid inputs < 5e5.