6.3.2 IEEE Extreme Value Functions (Sun Studio 12: Fortran Programming Guide)

Sun Studio 12: Fortran Programming Guide

6.3.2 IEEE Extreme Value Functions

The compilers provide a set of functions that can be called to return a special IEEE extreme value. These values, such as infinity or minimum normal, can be used directly in an application program.

Example: A convergence test based on the smallest number supported by the hardware would look like:

      IF ( delta .LE. r_min_normal() ) RETURN

The values available are listed in the following table:

Table 6–3 Functions Returning IEEE Values


IEEE Value	Double Precision	Single Precision
`infinity`	`d_infinity()`	`r_infinity()`
`quiet NaN`	`d_quiet_nan()`	`r_quiet_nan()`
`signaling NaN`	`d_signaling_nan()`	`r_signaling_nan()`
`min normal`	`d_min_normal()`	`r_min_normal()`
`min subnormal`	`d_min_subnormal()`	`r_min_subnormal()`
`max subnormal`	`d_max_subnormal()`	`r_max_subnormal()`
`max normal`	`d_max_normal()`	`r_max_normal()`

The two NaN values (quiet and signaling) are unordered and should not be used in comparisons such as IF(X.ne.r_quiet_nan())THEN... To determine whether some value is a NaN, use the function ir_isnan(r) or id_isnan(d).

The Fortran names for these functions are listed in these man pages:

libm_double(3f)
libm_single(3f)
ieee_functions(3m)

Also see:

ieee_values(3m)
The floatingpoint.h header file and floatingpoint(3f)