/MATH_LIBRARY=option (Alpha only) D=/MATH_LIBRARY=ACCURATE

 /MATH_LIBRARY

 Controls selection of math library routines to provide accurate or
 fast results for VSI Fortran intrinsic functions, such as SQRT.

 The default is /MATH_LIBRARY=ACCURATE.

 This qualifier applies only to IEEE data types (when you specify
 /FLOAT=IEEE_FLOAT).

 You can only specify one of the qualifier options.

 ACCURATE
   Causes the compiler to produce the very accurate results and
   error checking expected of quality compiler products.  It uses
   the standard set of math library routines for the applicable
   intrinsics.

   The standard math library routines are designed to obtain very
   accurate "near correctly rounded" results and provide the
   robustness needed to check for IEEE exceptional argument values,
   rather than achieve the fastest possible run-time execution
   speed.  Using /MATH_LIBRARY=ACCURATE allows user control of
   arithmetic exception handling with the /IEEE_MODE qualifier.

 FAST
   Causes the compiler to use versions of certain math library
   routines that perform faster computations than the standard, more
   accurate math library routines, but with slightly less fractional
   accuracy and less reliable arithmetic exception handling.  Using
   /MATH_LIBRARY=FAST allows certain math library functions to get
   significant performance improvements when the applicable
   intrinsic function is used.

   If you specify /MATH_LIBRARY=FAST, the math library routines do
   not necessarily check for IEEE exceptional values and the
   /IEEE_MODE qualifier is ignored.

   When you use MATH_LIBRARY=FAST, you should carefully check the
   calculated output from your program to verify it is not relying
   on the full fractional accuracy of the floating-point data type
   to produce correct results.  You should also verify that the
   calculated output is not producing unexpected exceptional values
   (exception handling is indeterminate).

   Programs that do not produce acceptable results with
   /MATH_LIBRARY=FAST and single-precision data might produce
   acceptable results if they are modified (or compiled) to use
   double-precision data.

   The specific intrinsic routines that have special fast math
   routines depend on the version of the OpenVMS Alpha operating
   system in use.  Allowed error bounds vary with each routine.