Instruction Set

[HiRez]

Greetings,

I could not locate an “Instruction Set” document.
At the very least, could someone please tell me what the {rn,rz,ru,rd} suffixes mean (as in __dmul_rn(x,y))?
Thanks in advance.

[Gregory_Diamos]

Greetings,

I could not locate an “Instruction Set” document.

At the very least, could someone please tell me what the {rn,rz,ru,rd} suffixes mean (as in __dmul_rn(x,y))?

Thanks in advance.

They are the basic rounding modes for ieee754. RN = Round to Nearest, RZ = Round towards Zero

RU is not the same notation as used in the ISA docs, but I assume that it is the same as RP (Round to Positive infinity), maybe they mean round up?

similarly, I think that RD refers to RM (Round to negative infinity), or maybe round down?

These are covered in the PTX ISA docs: http://www.gdiamos.net/classes/translator/ptx_isa_1.4.pdf

[Cygnus_X1]

To confirm Gregory’s explanation, a quote from Programming Guide, chapter C.2, page 124:

Functions suffixed with _rn operate using the round-to-nearest-even rounding mode.

Functions suffixed with _rz operate using the round-towards-zero rounding mode.

Functions suffixed with _ru operate using the round-up (to positive infinity) rounding mode.

Functions suffixed with _rd operate using the round-down (to negative infinity) rounding mode.

Chapter C.1 covers standard functions and C.2 - intristic functions available to you in CUDA.