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Re: RandomReal gets stuck

  • To: mathgroup at smc.vnet.net
  • Subject: [mg100426] Re: RandomReal gets stuck
  • From: Bas Straatman <bastraat at ucalgary.ca>
  • Date: Wed, 3 Jun 2009 01:11:33 -0400 (EDT)
  • Organization: The University of Calgary
  • References: <gvq0eu$n31$1@smc.vnet.net> <gvtmeb$gdh$1@smc.vnet.net> <h02vdq$80k$1@smc.vnet.net>

Not in version 5.2, (it doesn't have RandomReal but it has the old 
Random). That's what I am using now until a new release comes out. 
Wolfram Research has confirmed that the new release will have this bug 
fixed.

Bas



Szabolcs wrote:
> On May 31, 1:33 pm, "Sjoerd C. de Vries" <sjoerd.c.devr... at gmail.com>
> wrote:
>> Hi Bas,
>>
>> I can confirm this bug.
>>
>> Executing an even simpler version, namely
>>
>> Maximize[Plus @@ Table[y[i], {i, 31}], Table[y[i], {i, 31}]];
>>
>> will also set the random generator to a fixed starting point. The
>> number 31 is crucial, as lower values do not appear to cause the bug,
>> while higher values do. Changing Plus to Times appears to prevent the
>> bug.
>>
>> In[394]:= Table[
>>  Maximize[Plus @@ Table[y[i], {i, 31}], Table[y[i], {i, 31}]];
>>  RandomReal[],
>>  {20}
>>  ]
>>
>> During evaluation of In[394]:= Maximize::natt: The maximum is not
>> attained at any point satisfying the given constraints.  >>
>>
>> Out[394]= {0.455719, 0.455719, 0.455719, 0.455719, 0.455719, \
>> 0.455719, 0.455719, 0.455719, 0.455719, 0.455719, 0.455719, 0.455719,
>> \
>> 0.455719, 0.455719, 0.455719, 0.455719, 0.455719, 0.455719, 0.455719,
>> \
>> 0.455719}
>>
>> This is very nasty, as a lot of people critically depend on random
>> functions to be random. I would urge you to report this to wolfram
>> support.
>>
> 
> The problem is present both in version 6.0.3 and version 7.0.1.
> 


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