Speeding up calculations by lowering the precision ?

*To*: mathgroup at smc.vnet.net*Subject*: [mg7913] Speeding up calculations by lowering the precision ?*From*: "Frank" <F.J.M.Geurts at fys.ruu.nl>*Date*: Mon, 21 Jul 1997 03:22:05 -0400*Organization*: Universiteit Utrecht*Sender*: owner-wri-mathgroup at wolfram.com

Hi, I've written a lengthy math file which will eventually perform some numerical calculations based on a couple of NIntegrate's. Right now, these calculations take a very long time on a 466Mhz Alpha (running Math 2.2.4 / Digital Unix 4.0). In fact i'be estimated another month (!). Everything runs under 'default' conditions, i.e. Precision and WorkingPrecision are based on the $MachinePrecision (which is 16). However, I am not really interested in this high Precision but in high Speed : I would like all my calculations to be performed at a 4-5 digit precision. I'm getting rather confused of the actual Precision since after forcing NIntegrate with WorkingPrecision->8 and PrecisionGoal->4 Mathematica still claims 16digit precision in the results ... Can anybody help me out on these two questions: 1) Can (extensive) calculations be speeded up by lowering the Precision _below_ the $MachinePrecision ? 2) How can I be sure that all the calculations will be at a maximum precision set by me, without having to control/adjust each NIntegrate ? best regards, Frank --- F.J.M. Geurts Dept. Subatomic Physics Utrecht University R.J.v/d Graafflab. +31-30-2532210/1492 geurts at fys.ruu.nl p.o. box 80,000 fax: 2518689 http://www.fys.ruu.nl/~geurts 3508 TA Utrecht The Netherlands