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Re: V8 slow like a snail

  • To: mathgroup at smc.vnet.net
  • Subject: [mg127732] Re: V8 slow like a snail
  • From: "Alexey Popkov" <lehin.p at gmail.com>
  • Date: Fri, 17 Aug 2012 03:45:24 -0400 (EDT)
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"Dr. Wolfgang Hintze" <weh at snafu.de> ÓÏÏÂÝÉÌ/ÓÏÏÂÝÉÌÁ × ÎÏ×ÏÓÔÑÈ ÓÌÅÄÕÀÝÅÅ: 
news:k0fjaj$q71$1 at smc.vnet.net...
> Great disappointment on my side with 8.0.4.0 Home edition which I
> installed yesterday!
> My first impression: looks good, many nice features ... but incredibly
> slow in comparision to my good old 5.2.
> I then carried out a modest benchmark test the results of which I'll
> show below and which I like to express in terms of a "snail
> factor" ( = time in v5.2/ time in v8).
>
> Consider this integral for which we can safely expect Mathematica to
> be expert in solving:
>
> f1[n_, m_] :=
> Integrate[n t^m Exp[-n t] (Exp[t] - 1)^(n - 1), {t, 0, \[Infinity]},
>  Assumptions -> {{n, m} \[Element] Integers, m >= 0, n > 0}]
>
> I carried out Timing[f1[n, m]] for m=0,1,2,3,10 in both versions. Here
> are the results in the format
>
> {m, V5.2 f1 first call, V5.2 second call, V8 first call, V8 second
> call, snail factor first call, snail factor second call}
>
> {
> { 0, 0.328, 0.078, 2.122, 2.044, 6.46951, 26.2051},
> { 1, 0.109,  0.063, 30.202, 30.483, 277.083, 483.857},
> { 2, 0.421, 0.11,  30.42, 30.17, 72.2565, 274.273},
> { 3, 0.452, 0.156, 31.528, 31.325, 69.7522, 200.801},
> {10, 5.366, 5.382, 42.448, 42.682, 7.91055, 7.93051}
> }
>
> Even if we compare only the first calls the range of the snail factor
> goes up to 277 at m = 1, is 72 for m = 2, and is still close to 8 for
> larger m.
>
> This is my story in other words: I own a very old car, and have
> considered for a long time to change to a newer one - although it
> still can go at 200 km/h on the Autobahn.
> So now I am proud owner of the new brilliant car, and I must learn the
> on important tours (m=1) =EDts maximum speed turns out to be less than 1
> km/h,  about 3 km/h (m=2) or at most about 30 km/h. Who laughes? Me
> not! Obviously I'll definitely keep the old car!
>
> Ok, maybe I have chosen the wrong example (though in other test runs a
> similar pictures emerged and this example is just the type I'm using
> Mathematica for). Are there perhaps acknowleged benchmarks for such a
> comparison of versions?
>
> Finally, dear group, as you might have noticed, I'm asking for
> consolation. Please comment and give me useful hints. Many thanks in
> advance.
>
> Best regards,
> Wolfgang
>

There is a way to use MathKernel of version 5.2 from the version 8 
transparently via MathLink. It is as easy as defining

f1[n_, m_] :=
krn5Eval[Integrate[n t^m Exp[-n t] (Exp[t] - 1)^(n - 1), {t, 0, 
\[Infinity]},
Assumptions -> {{n, m} \[Element] Integers, m >= 0, n > 0}]]
(where krn5Eval[] is a function that transparently uses version 5 for 
evaluating its argument).

You can find more information in this thread:

http://stackoverflow.com/questions/4983301/executing-code-in-v-5-2-kernel-from-within-v-7-01-session-through-mathlink

HTH,

Alexey







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