fesetflushtozero(3M)					  fesetflushtozero(3M)

NAME
       fesetflushtozero() - set floating-point underflow mode

SYNOPSIS
DESCRIPTION
       The  function  sets  the current underflow mode.	 If the argument is 1,
       the underflow mode is set to flush-to-zero mode.	 If  the  argument  is
       zero,  the underflow mode is set to IEEE-754-compliant (gradual) under‐
       flow mode.  For arguments other than 1 or zero,	the  effect  is	 unde‐
       fined.

       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  HP  Integrity	 servers.   In
       IEEE-754-compliant  mode,  cases that might underflow 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 Integrity servers, flush-to-zero mode causes a zero  to  be  substi‐
       tuted  for  denormal  results (but not operands), without trapping into
       the kernel.

       Flush-to-zero mode may offer a significant 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	state‐
       ment),  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 pre‐
       vent  optimizations  that  can undermine the specified behavior of this
       function.

       Link in the math library by specifying on the compiler or  linker  com‐
       mand line.

       For more information, see the at the following site:

RETURN VALUE
       None.

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
       fegetflushtozero(3M), fenv(5).

							  fesetflushtozero(3M)

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