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/Qprec-sqrt documentation

jimdempseyatthecove
Honored Contributor III
‎04-05-2016 08:16 AM
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When issuing ifort /? to list the options we see:

/Qprec-sqrt[-]
          determine if certain square root optimizations are enabled

Shouldn't this enable (full) precision, or disable (fast) precision of square root?

Jim Dempsey

 

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Steven_L_Intel1
Employee
‎04-05-2016 08:23 AM
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Default

-no-prec-sqrt
or /Qprec-sqrt-

The compiler uses a faster but less precise implementation of square root.

However, the default is -prec-sqrt or /Qprec-sqrt if any of the following options are specified: /Od, /fltconsistency, or /Qprec on Windows* systems; -O0 , -fltconsistency, or -mp1 on Linux* and OS X* systems.

Description

This option improves precision of square root implementations. It has a slight impact on speed.

This option inhibits any optimizations that can adversely affect the precision of a square root computation. The result is fully precise square root implementations, with some loss of performance.

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