fegetflushtozero man page on HP-UX

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fegetflushtozero(3M)					  fegetflushtozero(3M)

       fegetflushtozero() - get floating-point underflow mode

       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 trap‐
       ping into the kernel.  Flush-to-zero mode may offer a significant  per‐
       formance improvement for some applications.

       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

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

       For more information, see the at the following site:

       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.

       No errors are defined.

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

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

       fesetflushtozero(3M), fenv(5).


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