#pragma fragmentoption ARB_precision_hint_fastest any documentation about this?

I don't know nothing about this kind of commands. any documentation ? I need some references. and any other commands?

 

https://www.opengl.org/registry/specs/NV/fragment_program4.txt

"+ Precision Hints (ARB_precision_hint_fastest, ARB_precision_hint_nicest)

Fragment program computations are carried out at an implementation-
dependent precision. However, some implementations may be able to perform
fragment program computations at more than one precision, and may be able
to trade off computation precision for performance.

If a fragment program specifies the "ARB_precision_hint_fastest" program
option, implementations should select precision to minimize program
execution time, with possibly reduced precision. If a fragment program
specifies the "ARB_precision_hint_nicest" program option, implementations
should maximize the precision, with possibly increased execution time.

Only one precision control option may be specified by any given fragment
program. A fragment program that specifies both the
"ARB_precision_hint_fastest" and "ARB_precision_hint_nicest" program
options will fail to load."

 

thx,you do a lot of help for me