Dear Evgeni,

Thank you for your answer.  Now I think I undestand, even though the sequence generated is the same with the same seed, the program keeps running additional measurements until checked by the scheduler.


Thanks,

Marcelo Guimaraes

2012/1/21 Evgeni Burovski <evgeny.burovskiy@gmail.com>

Dear Marcelo,

[while I'm not Matthias, I'd dare adding my 2pence nonetheless]

Look at the COUNT field of your output files. The number of measurements taken is different in all your runs --- therefore the results are different.

As far as I understand, the number of MC is not guaranteed in current versions of ALPS applications. (Maybe someone more knowledgeable can comment on this?)
Especially for short runs, the actual number of MC steps is almost always larger than the number you request in the parameter files.

To make a meaningful comparison of equivalent runs you need to take errorbars into account, just as Matthias said in his previous email.

Cheers,

Zhenya

2012/1/21 Marcelo Guimarães <marcelosg@gmail.com>

Dear Matthias,

Thank you for your answer. But I think I did not made myself clear.

I used the same input file , and ran it twice with alps 1.35 obtaining different results in each run. Using the same input file and running twice with alps 2.00.rc4 I got different results. All 4 results were different from each other.

I could not obtain exactly the same results even using the same code and the same SEED in either versions. Am I doing something wrong? Or the result could never actually be the same?

In case it helps, this is the input file used in all runs:
FILE:parameter

LATTICE="simple cubic lattice"
MODEL   = "spin"
ALGORITHM="sse"
MEASURE[Structure Factor]=false
MEASURE[Correlations]=false
MEASURE[Specific Heat]=true
MEASURE[Stiffness]=true
MEASURE[Magnetization]=true
WHICH_LOOP_TYPE="locopt"
EPSILON=0.5
local_S=1
J=-1
J0=-1
J1=-1
Jz=0
Jz'=0
{THERMALIZATION=10000;L=04;BETA=0.10;SWEEPS=1000;D=10.0;SEED=814}

I converted it with parameter2xml

Then I executed the dirloop_see v1.1 for alps 1.3.5:
dirloop_sse --Tmin=10 parameter.in.xml

with the result:
...
   <SCALAR_AVERAGE name="Energy">
      <COUNT>8519</COUNT>
      <MEAN method="simple">250.472</MEAN>
...
Then I repeated the command:
dirloop_sse --Tmin=10 parameter.in.xml

and obtained the result:
...
<SCALAR_AVERAGE name="Energy">
      <COUNT>3009</COUNT>
      <MEAN method="simple">250.553</MEAN>
...

The same goes for the dirloop 4.1 based on alps 2.0.0rc4 code:
same parameters same SEED:

 After extracting values with "convert2xml parameter.task1.out.run1"  the 1st run produced:
<SCALAR_AVERAGE name="Energy">
      <COUNT>1473</COUNT>
      <MEAN method="simple">251.784</MEAN>

And in the 2nd run:
 <SCALAR_AVERAGE name="Energy">
      <COUNT>16076</COUNT>
      <MEAN method="simple">250.616</MEAN>


Marcelo Guimarães

2012/1/21 Matthias Troyer <troyer@phys.ethz.ch>

Hi Marcello,

Indeed if the same SEED is used you get the same results if the same code is taken. However, dirloop_sse was completely rewritten between 1.3 and 2.0. It is a new code. Thus the results should now only agree within error bars.

Matthias

On Jan 20, 2012, at 6:56 PM, Marcelo Guimarães wrote:

> Dear All,
>
> I was wondering if using the same SEED parameter with the dirloop_sse application in different runs should produce exactly the same results.
>
> It is defined as " The random number seed used in the next run.". But I failed to produce the same results with alps 1.35 or with alps 2.02.
>
>
> Regards,
>
> Marcelo Guimarães