VMS Help FORTRAN, /MATH_LIBRARY  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  /[NO]MATH_LIBRARY=(option[,...])        D=/MATH_LIBRARY=(ACCURATE,NOV5)

  Specifies the selection of math library routines used to implement
  mathematical intrinsic functions.  The qualifier is not negatable
  and a value must be specified.  If the ACCURATE and FAST keywords
  are both specified, the last keyword is used.

  Additional Information (explode) :

• ACCURATE
• FAST
• V5