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Topic: problem on record-breaking values in probability
Replies: 14   Last Post: Apr 14, 2013 11:36 PM

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James Waldby

Posts: 347
Registered: 1/27/11
Re: problem on record-breaking values in probability
Posted: Mar 11, 2013 2:07 AM
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On Sun, 10 Mar 2013 21:47:27 -0400, David Bernier wrote:
> On 03/10/2013 08:52 PM, David Bernier wrote:
>> On 03/01/2013 08:41 AM, David Bernier wrote:
>>> On 02/27/2013 10:24 PM, David Bernier wrote:
>>>> On 02/27/2013 04:05 PM, James Waldby wrote:
>>>>> On Wed, 27 Feb 2013 07:10:08 -0500, David Bernier wrote:
>>>>>> On 02/27/2013 05:49 AM, David Bernier wrote:
>>>>>>> On 02/27/2013 05:31 AM, David Bernier wrote:
>>>>>>>> I used Marsaglia's 64-bit SUPER KISS pseudo-random number generator
>>>>>>>> to simulate uniform r.v.s on [0, 1] that are independent, as
>>>>>>>> X_1, X_2, X_3, ad infinitum
>>>>>>>>
>>>>>>>> For each go, (or sequence) I define its 1st record-breaking value
>>>>>>>> as R(1) as X_1, its 2nd record-breaking value R(2) as the
>>>>>>>> value taken by X_n for the smallest n with X_n > X_1, and in general

>>>>> [ R(k+1) is the value taken by X_n for the smallest n with X_n > R(k)]
>>>>> ...

[snip]
>>>>> [etc]
>>>>>
>>>>> It would be useful to report the number of trials each simulation
>>>>> took to find its 20th RBV. If a simulation takes m trials, the

[snip]
>>>>> In following, let L(n) = Pr(n'th item of n is lowest). (Distribution
>>>>> of the lowest item should be similar to distribution of 1-(highest
>>>>> item).) I suppose that L(n) = 1/n and that the expected value of the
>>>>> number of record-low-values (RLV's) in m trials is sum{i=1 to m}(1/i),
>>>>> or about H_m, the m'th harmonic number, which can be approximated by
>>>>> log(m) + gamma, with gamma = Euler-Mascheroni constant, about 0.5772.

[snip]
>>> In the literature, a remarkable article, which may have
>>> appeared in the Am. Math. Monthly, can be found by
>>> searching for:
>>> Breaking Records and Breaking Boards. Ned Glick

...
>> I did long simulations for 12th Record-Breaking Values.
>>
>> With MatLab, I constructed a histogram of the natural
>> logarithms of the 76,000 values:
>>
>> < http://img521.imageshack.us/img521/7702/records12log.jpg > .

...
> S_12 is number of trials (steps) taken to find the 12th
> Record-Breaking Value. On Average, log(S_12) is close
> to 12 - gamma (gamma is the Euler-Mascheroni constant).
>
> A number of 76,000 sequences were generated, each being
> continued until the 12th Record-Breaking Value for
> that sequence was found. There is such variance from
> one sample S_12 to another that I prefer the
> quantities log(S_12) , for the histograms.
>
> Occasionally, an unusually high record is attained
> in the 1st, 2nd, ... or 11th Record-Breaking Value.
> That makes breaking the record all the more difficult.
> In the simulations, the computer would pass (say) three
> hours or more on the same sequence, with no new output
> to the file for three or more hours.


You may already have done so, but if not and if you are going to
run more simulations, consider (a) profiling the code, and
(b) trying different compilation options. (a) allows you to find
out which lines of code use most of the hours of CPU time, so you
can try alternate ways of coding them. Under (b), starting with
the same random seed in each case, try optimization options -O1,
-O2, -O3, -Ofast, timing the execution and also verifying the
same results. From my interpretation of URL below, those 4
optimization options are all you need to try.
<http://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html>

--
jiw





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