set_ieee_rounding_mode(3I)

NAME
     SET_IEEE_ROUNDING_MODE - Alters current floating-point rounding mode
     state and restores the floating-point rounding mode before exiting a
     procedure

SYNOPSIS
     SET_IEEE_ROUNDING_MODE ([ROUNDING_MODE=]rounding_mode)

IMPLEMENTATION
     UNICOS/mk and IRIX systems

     CRAY T90 systems that support IEEE arithmetic

STANDARDS
     CF90 and MIPSpro 7 Fortran 90 compiler extension to Fortran 90

     IEEE Standard for Binary Floating-point Arithmetic

DESCRIPTION
     The SET_IEEE_ROUNDING_MODE intrinsic subroutine is typically used to
     alter the current floating-point rounding mode state and to restore
     the caller's floating-point rounding mode just before exiting a
     procedure.  It accepts the following argument:

     rounding_mode
               Must be scalar and of an integer type that occupies a full
               word.  It is an INTENT(IN) argument.

               The floating-point rounding mode is set to the rounding mode
               indicated by rounding_mode.

               rounding_mode must have one of the values represented by the
               following named constants:

               * IEEE_RM_NEAREST

               * IEEE_RM_POS_INFINITY

               * IEEE_RM_ZERO

               * IEEE_RM_NEG_INFINITY

               rounding_mode is assumed to have been set through an
               invocation of GET_IEEE_ROUNDING_MODE(3I).

     The IEEE_REAL(3I) and IEEE_INT(3I) functions are the only routines
     supplied by Cray Research that examine the setting of the rounding
     mode on CRAY T90 systems that support IEEE arithmetic, UNICOS/mk
     systems, and IRIX systems.

     The name of this intrinsic cannot be passed as an argument.

NOTES
     The IEEE intrinsic procedures use the named constants contained in a
     system module, so you must include one of the following statements in
     your program:

     * On UNICOS and UNICOS/mk systems:  USE CRI_IEEE_DEFINITIONS

     * On UNICOS, UNICOS/mk, and IRIX systems:  USE FTN_IEEE_DEFINITIONS

     The CRI_IEEE_DEFINITIONS module is obsolescent.  It will be removed
     for the CF90 4.0 release.

EXAMPLES
        ! Assume the following code is executing on a machine where default
        ! integer occupies a full word.

        INTEGER  save_rounding_mode

        ! Save the current rounding mode then change the rounding mode
        ! to round to positive infinity.

        CALL GET_IEEE_ROUNDING_MODE(save_rounding_mode)
        CALL SET_IEEE_ROUNDING_MODE(IEEE_RM_POS_INFINITY)

        ! Calculate the upper bound on sum.

        DO i = 1, n
           xup(i)  = y(i) + z(i)
        END DO

        ! Reset to round to negative infinity mode.

        CALL SET_IEEE_ROUNDING_MODE(IEEE_RM_NEG_INFINITY)

        ! Calculate lower bound on sum.

        DO i = 1, n
           xdn(i) = y(i) + z(i)
        END DO

        ! Restore original rounding mode and return to the caller.

        CALL SET_IEEE_ROUNDING_MODE(save_rounding_mode)

SEE ALSO
     GET_IEEE_ROUNDING_MODE(3I)

     Intrinsic Procedures Reference Manual, publication SR-2138, for the
     printed version of this man page.