rcp.approx.ftz.f64 GPU Virtual ISA NVIDIA

rcp.approx.ftz.f64 Floating-Point Instructions

rcp.approx.ftz.f64 d, a;

Compute a fast, gross approximation to the reciprocal as follows: extract the most-significant 32 bits of.f64 operand a in 1.11.20 IEEE floating-point format (i.e., ignore the least-significant 32…

Encoding

PTX is a virtual instruction set. It has no single, stable native binary encoding - the compiler lowers this instruction to different native machine code depending on the selected NVIDIA target architecture (compute capability). This page intentionally shows no bit-diagram; see the target/version requirements below for what governs how this instruction compiles.
PTX ISA Version Introduced PTX ISA 2.1
Minimum Target sm_20

Syntax Forms

One mnemonic covers many type / state-space / scope / modifier combinations - each row below is an independently valid form.

Syntax Data Types State Space(s) Modifiers Min. Target Description
rcp.approx.ftz.f64 d, a; sm_20 Compute a fast, gross approximation to the reciprocal as follows: extract the most-significant 32 bits of.f64 operand a in 1.11.20 IEEE floating-point format (i.e. (see the official PTX ISA docs for the full description)

Operands

  • d
    Destination register
  • a
    Source operand

At a Glance

Data Types -

Related

More in Floating-Point Instructions

Reference

NVIDIA PTX ISA

Description

Compute a fast, gross approximation to the reciprocal as follows: extract the most-significant 32 bits of.f64 operand a in 1.11.20 IEEE floating-point format (i.e., ignore the least-significant 32 bits of a ), compute an approximate.f64 reciprocal of this value using the most-significant 20 bits of the mantissa of operand a, place the resulting 32-bits in 1.11.20 IEEE floating-point format in the most-significant 32-bits of destination d,and zero the least significant 32 mantissa bits of.f64 destination d.

Semantics

tmp = a[63:32]; // upper word of a, 1.11.20 format d[63:32] = 1.0 / tmp; d[31:0] = 0x00000000;

Examples

rcp.approx.ftz.f64  xi,x;

Reproduced from NVIDIA's official PTX ISA documentation for technical accuracy.

Sources