fegetflushtozero(3M)													      fegetflushtozero(3M)

NAME

       fegetflushtozero() - get floating-point underflow mode

SYNOPSIS

DESCRIPTION

       The  function  retrieves  the value representing the current underflow mode, which is either IEEE-754-compliant (gradual) underflow mode or
       flush-to-zero mode.

       The default underflow mode is IEEE-754-compliant.

       Flush-to-zero mode, also known as fast underflow mode, is supported on most PA1.1 systems and on all PA2.0  and	Itnaium(R)-based  systems.
       In  IEEE-754-compliant  mode,  underflow cases may be handled by trapping into the kernel, where the IEEE-mandated conversion of the result
       into a denormalized value or zero is accomplished by software emulation.  On PA-RISC systems, flush-to-zero mode allows the substitution of
       a zero for denormal operands and operation results, without trapping into the kernel.  On HP Integrity servers, flush-to-zero mode causes a
       zero to be substituted for denormal results (but not operands), without trapping into the kernel.  Flush-to-zero mode may offer a  signifi-
       cant performance improvement for some applications.

USAGE

       To use this function, compile either with the default option or with the and options.  Make sure your program includes

       For Integrity servers, specify on the compiler command line or place the call to this function under the effect of an affirmative pragma:

       If  the pragma is placed outside of any top-level declarations in a file, the pragma will apply to all declarations in the compilation fol-
       lowing the pragma until another pragma is encountered or until the end of the file is reached.

       If the pragma is placed at the beginning of a block (compound statement), the pragma will apply until  another  pragma  is  encountered	or
       until the end of the block is reached.

       For  PA-RISC, you might need to use the compiler option in order to prevent optimizations that can undermine the specified behavior of this
       function.

       Link in the math library by specifying on the compiler or linker command line.

       For more information, see the at the following site:

RETURN VALUE

       The function returns zero if the current underflow mode is IEEE-754-compliant.  The function returns 1 if the  current  underflow  mode	is
       flush-to-zero.

       On systems that do not support flush-to-zero mode, this function returns an undefined value.

ERRORS

       No errors are defined.

EXAMPLES

       Save the current underflow mode, set flush-to-zero mode, and restore the previous mode.

AUTHOR

       was developed by HP and is not required by any current standard.

SEE ALSO

       fesetflushtozero(3M), fenv(5).

															      fegetflushtozero(3M)