Acos

Function Acos

The Acos function computes an arccosine.

Performance:

	Default processor	Pentium® III processor	Pentium® 4 processor	Itanium® processor
vsAcos (HA version)	66.2	43.6	25.0	10.2
vdAcos (HA version)	97.3	97.3	69.9	15.4

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 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
vsAcos (HA version)	0.54	0.79	0.76	0.50
vdAcos (HA version)	0.64	0.64	0.77	0.51

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
vsAcos/vdAcos (HA version)	1	0	+	+	+	+
	NaN (Both QNaN and SNaN)	NaN (Raise Invalid Exeption for SNaN)	+	+	+	+
	+/- Inf	NaN	+	+	+	+
	\|x\|>1	NaN (Raise Invalid Exeption)	+	+	+	+
	0	Machine PI/2	+	+	+	+
	-1	Machine PI	+	+	+	+

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