Re: Vectorization

*To*: mathgroup at smc.vnet.net*Subject*: [mg60671] Re: [mg60623] Vectorization*From*: Zhengji Li <zhengji.li at gmail.com>*Date*: Fri, 23 Sep 2005 04:20:41 -0400 (EDT)*References*: <200509220608.CAA01888@smc.vnet.net>*Reply-to*: Zhengji Li <zhengji.li at gmail.com>*Sender*: owner-wri-mathgroup at wolfram.com

Marcelo, That's because the construction of the LONG complex vector uses far more time than long real vector. To simplify the matter, just throw Sin away: Table[I Random[], {1000000}] // Timing // First I Table[I Random[], {1000000}] // Timing // First 1.983 Second, 3.786 Second. The frist one is the contruction ONE complex vector, while in the second one another vector is contructed due to the I * {...} operation. And 3.786 Second is about 2 * 1.983 Second. As a comparision, Table[Random[], {1000000}] // Timing // First 2 Table[Random[], {1000000}] // Timing // First 0.29 Second, 0.411 Second. In your example, Table[Sin[I Random[]],{1000000}]//Timing//First will generate only one complex vector, while Sin[Table[I Random[],{1000000}]]//Timing//First will generate two complex vectors. ----- The time saved by vectorization is less than that used by the contruction of a complex vector. -- Li Zhengji ------------------------------------------------------------- If all you have is a hammer, everything is a nail. -------------------------------------------------------------

**References**:**Vectorization***From:*"Marcelo Mayall" <mmayall@bol.com.br>