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fortran
.HLP
Directs the compiler to select the standard version of the math
library routines used to implement vectorized references to the
ATAN, COS, EXP, LOG, LOG10, SIN, SQRT and TAN intrinsics as well
as the exponentiation operator ** for real data types. This
version gives the most accurate result. For certain ranges of
input values, the selected routine can execute more slowly than
the alternate version specified by FAST. This keyword is not
negatable.

Directs the compiler to select the Fast Vector Math version of
library routines used to implement vectorized references to the
ATAN, COS, EXP, LOG, LOG10, SIN, SQRT and TAN intrinsics as well
as the exponentiation operator ** for real data types. This
version gives the highest execution performance. For certain
ranges of input values, the selected routine may not give a
result that is as accurate as the version specified by ACCURATE.
Accuracy reduction will be at most 2 bits for single-precision
routines, and at most 4 bits for double-precision routines. This
keyword is not negatable.

Controls whether the compiler restricts its use of math library
routines to those provides in OpenVMS VAX V5.4. If V5 is specified,
the compiler does not use optimized versions of the math library
routines for scalar references to the AMOD, ATAN, ATAN2, CABS,
CCOS, CEXP, CLOG, COSH, CSIN, CSQRT, SIGN, SINH and TANH intrinsic
functions nor does it vectorize references to the ATAN2, CCOS,
CEXP, COSH, CSIN, CSQRT, MOD, SINH and TANH intrinsic functions.
The default is NOV5 which enables the above optimizations and
vectorizations, making use of new math library routines which are
provided with the DEC Fortran product but which are not present
in OpenVMS VAX versions V5.4 through V6.0.