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I wanted to check something, but ran into troubles using HistogramDistribution in combination with ParallelTable.

The code does the following: Compute a HistogramDistribution of some sample and use some function which draws from that HistogramDistribution. Here's a stripped down version of the code that reproduces my problem:

exampledist = 
  TruncatedDistribution[{0, 1.16}, 
   HistogramDistribution[
    RandomVariate[ExponentialDistribution[1], 1000], 3]];
SetSharedVariable[exampledist];

drawExample[n_] :=

  Module[{draws = Table[0, {n}]},
   (*check some stuff, do something*)
   For[i = 1, i <= n, i++,
    draws[[i]] = First[RandomVariate[exampledist, 1]];
    ];
   Return[draws];
   ];

drawExample[3]
ParallelTable[Table[drawExample[3], {1}], {i, 1, 2}]

The output is:

{1.05817, 1.05732, 0.47069}

and

{{{DataDistribution[<<"Histogram">>, {1000}], DataDistribution[<<"Histogram">>, {1000}], DataDistribution[<<"Histogram">>, {1000}]}}, \ {{DataDistribution[<<"Histogram">>, {1000}], DataDistribution[<<"Histogram">>, {1000}], DataDistribution[<<"Histogram">>, {1000}]}}}

Why can't I use the distribution in ParallelTable? First I thought the definition isn't shared properly, so I added SetSharedVariable, but that didn't resolve it. Does anyone know what I am missing here? Thank you very much.

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  • $\begingroup$ This just works for me. What version are you using (evaluate $Version)? $\endgroup$ – Andy Ross Dec 15 '12 at 23:30
  • $\begingroup$ 8.0 for Linux x86 (64-bit) $\endgroup$ – user13655 Dec 16 '12 at 8:51
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This works. It has some redundancies, though, which I kept, because I don't know what this is part off.

exampledist = 
  TruncatedDistribution[{0, 1.16}, 
   HistogramDistribution[
    RandomVariate[ExponentialDistribution[1], 1000], 3]];


In[109]:= RandomVariate[exampledist, 10]

Out[109]= {0.912899, 0.628297, 0.349011, 0.650514, 0.232781, \
0.731322, 1.08089, 0.194195, 0.892419, 0.533181}

drawExample[n_] := RandomVariate[exampledist, n]

In[115]:= ParallelTable[Table[drawExample[15], {1}], {2}]

Out[115]= {{{1.04123, 0.904413, 0.370872, 0.999883, 0.160472, 
   0.924548, 0.522067, 0.899367, 0.224375, 0.33492, 0.765098, 
   0.463829, 0.820183, 0.524134, 0.480491}}, {{0.269976, 0.69883, 
   1.03064, 1.03798, 0.410801, 0.128295, 0.804953, 0.903301, 1.12766, 
   0.095034, 0.806157, 1.15963, 0.657254, 0.730021, 0.740129}}}
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  • $\begingroup$ I just tried your idea with the module and it gives the same problem. The module seems to cause the problems. However, I have to keep it because drawExample does some computations before. $\endgroup$ – user13655 Dec 15 '12 at 13:04
  • $\begingroup$ It works for me with Module. $\endgroup$ – asim Dec 15 '12 at 16:11
  • $\begingroup$ ok, ill give it a try again. thank you for your suggestion. $\endgroup$ – user13655 Dec 16 '12 at 8:49

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