Re: A zillion times slower in version 5

*To*: mathgroup at smc.vnet.net*Subject*: [mg46427] Re: A zillion times slower in version 5*From*: "Joshua A. Solomon" <J.A.Solomon at city.ac.uk>*Date*: Tue, 17 Feb 2004 07:46:45 -0500 (EST)*References*: <c0k3sd$8kn$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

David Whitoff, at Wolfram, replies: Evaluate $MaxPrecision=10^6 to restore Version 4 behavior. Otherwise 1-Exp[-(10^((x-a)/20))^b] will compute a result with a precision of about 5x10^8 Another possible solution is to rearrange the calculation so that subtracting an astonomically tiny quantity from an exact number doesn't come up, such as by using bug[x_, {a_, b_, c_, d_}] := c + (1 - c - d)(1.0 - Exp[-(10^((x - a)/20))^b]) > In[1]:= bug[x_,{a_,b_,c_,d_}]:=c+(1-c-d)(1-Exp[-(10^((x-a)/20))^b]) > > Using Mathematica 4... > > In[2]:= {$Version, $ReleaseNumber} > Out[2]:= {4.1 for Mac OS X (November 5, 2001),5} > > In[3]:= Timing[bug[-8,{-60,3.5,0.5,0.01}]] > Out[3]:= {0. Second,0.99} > > Using Mathematica 5... > > In[2]:= {$Version, $ReleaseNumber} > Out[2]:= {5.0 for Mac OS X (June 10, 2003),0} > > In[3]:= Timing[bug[-8,{-60,3.5,0.5,0.01}]] > Out[3]:= {6.21 Second,0.99} > > Six seconds! What is it doing? What is the best way to streamline this? > > js >