Re: Speed Up of Calculations on Large Lists
- To: mathgroup at smc.vnet.net
- Subject: [mg108988] Re: Speed Up of Calculations on Large Lists
- From: Ray Koopman <koopman at sfu.ca>
- Date: Fri, 9 Apr 2010 03:32:45 -0400 (EDT)
- References: <hpcjh0$mva$1@smc.vnet.net> <hphq5f$1h6$1@smc.vnet.net>
On Apr 7, 4:26 am, sheaven <karg.ste... at googlemail.com> wrote: > I did some testing and here is the outcome: > > [...] > > Drop is by far the fastest function You didn't give ListConvolve a fair test, because you defined the kernel as a list of exact rationals. If you define it as a list of reals, ListConvolve is just as fast as drop-type methods and does not lose precision. In[1]:= movAc[data_, days_] := Accumulate[ Prepend[Drop[data, days] - Drop[data, -days], Tr@Take[data, days]]]/days In[2]:= maDropF = Function[{vData, days}, With[{vAcc = Prepend[Accumulate@vData, 0.]}, Developer`ToPackedArray[(Drop[vAcc, days] - Drop[vAcc, -days])/ days, Real]]]; In[3]:= moCon[data_, days_] := ListConvolve[ConstantArray[1./days, days], data] In[4]:= data = 100 + Accumulate[RandomReal[{-1, 1}, {1*^4}]] ; In[5]:= AbsoluteTiming[ m0 = Table[MovingAverage[data, days], {days, 30, 250}];] Out[5]= {1.514497, Null} In[6]:= AbsoluteTiming[ m1 = Table[movAc[data, days], {days, 30, 250}];] {m1 == m0, Max@Abs[m1/m0 - 1]} Out[6]= {0.831964, Null} Out[7]= {False, 4.89608*10^-14} In[8]:= AbsoluteTiming[ m2 = Table[maDropF[data, days], {days, 30, 250}];] {m2 == m0, Max@Abs[m2/m0 - 1]} Out[8]= {0.892764, Null} Out[9]= {False, 5.38902*10^-13} In[10]:= AbsoluteTiming[ m3 = Table[moCon[data, days], {days, 30, 250}];] {m3 == m0, Max@Abs[m3/m0 - 1]} Out[10]= {0.823370, Null} Out[11]= {True, 1.11022*10^-16}