InvSqrt

Function InvSqrt

The InvSqrt function computes an inverse square root.

Performance:

	Default processor	Intel® Pentium® III processor	Intel® Pentium® 4 processor	Intel® Pentium® 4 processor with Streaming SIMD Extensions 3 (SSE3)	Intel® Itanium® 2 processor
vsInvSqrt (HA version)	22.00	8.15	6.20	6.91	5.14
vdInvSqrt (HA version)	32.59	32.13	19.29	22.40	6.17

Notes:
1) Units - CPE (Clocks per Element)
2) Performance was measured on "working" interval (double precision: [-1,1]; single precision: [-1,1] )
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 Intel® Pentium® III processor

Notes:
1) *           X87 code for all processors
2) **         Intel® Pentium® III processor
3) ***       Intel® Pentium® 4 processor
4) ****     Intel® Pentium® 4 processor with Streaming SIMD Extensions 3 (SSE3)
5) ***** Intel® Itanium® 2 processor
6) Logarithmic scale is used for "Vectors Size" axis

Maximal observed error for the whole function domain:

	Default processor	Pentium III processor	Pentium 4 processor	Pentium 4 processor with SSE3	Itanium 2 processor
vsInvSqrt (HA version)	0.9103	0.9103	0.9103	0.9103	0.5000
vdInvSqrt (HA version)	0.7811	0.7811	0.5000	0.5000	0.5002

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

Special values:

Function	Input Argument	Result	Default processor	Pentium III processor	Pentium 4 processor	Pentium 4 processor with SSE3	Itanium 2 processor
vsInvSqrt/vdInvSqrt (HA version)	0	+ Inf (Raise DZ Exeption)	+	+	+	+	+
	NaN	NaN	+	+	+	+	+
	x<0	NaN	+	+	+	+	+
	+ Inf	0	+	+	+	+	+
	- Inf	NaN	+	+	+	+	+

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