Ramiro
Posts:
26
Registered:
9/18/07
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Re: Help on compiling a function
Posted:
Jan 19, 2011 5:24 AM
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Thanks so much, this was the answer exactly. Just a small
clarification:
I have been going through the compiler documenttaion. If I do
On[ Compile::noinfo]
I get the following:
example1 =
Compile[{{n, _Real, 1}, {a, _Real}, {b, _Real}, {t, _Real, 1}},
Block[{tn = Total[n]},
b^a*Exp[LogGamma[tn + a] - (Total[LogGamma[n + 1]] + LogGamma[a]) +
Total[n*Log[t]] - (tn + a)*Log[Total[t] + b]]]];
example1[{97.6203, 8.4788, 21.4204, 46.1755}, 1,
1, {39.9342, 7.5820, 5.8656, 10.0553}] // AbsoluteTiming
Compile::noinfo: No information is available for compilation of
LogGamma[Compile`$3]. The compiler will use an external evaluation and
make assumptions about the return type. >>
Compile::noinfo: No information is available for compilation of
LogGamma[n+1]. The compiler will use an external evaluation and make
assumptions about the return type. >>
Compile::noinfo: No information is available for compilation of
LogGamma[a]. The compiler will use an external evaluation and make
assumptions about the return type. >>
{0.000087, 1.06265*10^-11}
But if I add the corresponding information about LogGamma and Total,
the function performs a bit slower:
In[109]:= Clear[example1];
example1 =
Compile[{{n, _Real, 1}, {a, _Real}, {b, _Real}, {t, _Real, 1}},
Block[{tn = Total[n]},
b^a*Exp[LogGamma[tn + a] - (Total[LogGamma[n + 1]] + LogGamma[a]) +
Total[n*Log[t]] - (tn + a)*
Log[Total[t] +
b]]], {{LogGamma[_], _Real}, {Total[_], _Real}}];
example1[{97.6203, 8.4788, 21.4204, 46.1755}, 1,
1, {39.9342, 7.5820, 5.8656, 10.0553}] // AbsoluteTiming
Out[110]= {0.000141, 1.06265*10^-11}
Why is this?
Thanks to everyone for their help again,
Ramiro
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