InvSqrt

Function InvSqrt

The InvSqrt function computes an inverse square root.

Performance:

	Default processor	Pentium® III processor	Pentium® 4 processor	Itanium® processor
vsInvSqrt (HA version)	21.9	8.1	6.4	5.2
vdInvSqrt (HA version)	32.2	31.8	19.5	6.3

Notes:
1) Units - CPE (Clocks per Element)
2) Performance was measured on "working" interval (double precision: [3e-308,10000]; single precision: [2e-38,10000])
3) Data - vectors of 1000 elements with random generated numbers
4) "Default" means X87 code for all IA-32 processors
5) Performance of "default" version was measured on Pentium® III processor

Notes:
1) *        X87 code for all processors
2) **      Pentium® III processor
3) ***    Pentium® 4 processor
4) **** Itanium® processor
5) Logarithmic scale is used for "Vectors Size" axis

Maximal observed error for the whole function domain:

	Default processor	Pentium® III processor	Pentium® 4 processor	Itanium® processor
vsInvSqrt (HA version)	0.57	0.97	0.97	0.50
vdInvSqrt (HA version)	0.77	0.77	0.50	0.50

Notes:
1) Units - ULP (Units in The Last Place)

Special values:

Function	Input Argument	Result	Default processor	Pentium® III processor	Pentium® 4 processor	Itanium® processor
vsInvSqrt/vdInvSqrt (HA version)	0	+ Inf (Raise DZ Exeption)	+	+	+	+
	NaN	NaN	+	+	+	+
	x<0	NaN	+	+	+	+
	+ Inf	0	+	+	+	+
	- Inf	NaN	+	+	+	+

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