On Aug 28, 2008, at 11:00 AM, comp-phys-alps-users- request@phys.ethz.ch wrote:
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Today's Topics:
- First alps trials (Jo?o Manuel Viana Parente Lopes)
- Re: First alps trials (Matthias Troyer)
Message: 1 Date: Wed, 27 Aug 2008 23:56:53 +0100 From: Jo?o Manuel Viana Parente Lopes jvianalopes@gmail.com Subject: [ALPS-users] First alps trials To: comp-phys-alps-users@phys.ethz.ch Message-ID: 40B2C500-9E6E-45A9-A170-91187657132C@gmail.com Content-Type: text/plain; charset="iso-8859-1"
Dear colleagues,
I'm making my first experiments with Alps... I was comparing the average energy for small temperatures (T~ 0.01, J = 1) in the 1D Heisenberg model with the exact solution for small open linear chains using the loop program with de SSE representation.
I notice that I can not decrease the error bars by the increase of the numbers of SWEEPS! How can I decrease the error bars?
Thanks in advance
Jo?o Lopes
PS: A sugestion: It would be very helpful if we could do a search in the mailing list Maybe this link could help: http://wiki.list.org/display/DOC/How+do+I +make+the+archives+searchable
That's what I was expecting!
But If I run a very simple calculation using the parameter file:
LATTICE_LIBRARY="/usr/local/lib/xml/lattices.xml" LATTICE="open chain lattice" MODEL="spin" local_S=1/2 J=1 L=3 THERMALIZATION=1500 MEASURE[Correlations]=true; SWEEPS=100 REPRESENTATION="path integral" {T=0.01;}
Measuring the Energy for several number of SWEEPS, I obtained after extract the results with extracttext:
#SWEEPS= 100 0.01 -1.000121 0.000784 #SWEEPS= 400 0.01 -1.00235 0.00344 #SWEEPS= 1600 0.01 -1.000065 0.00067 #SWEEPS= 6400 0.01 -0.999543 0.000744 #SWEEPS= 25600 0.01 -1.000038 0.000762 #SWEEPS= 102400 0.01 -1.000819 0.000497
The same thing happened with SSE representation... The error bars are not decreasing...
Please check in the output of the measurements how many measurements were actually done. For such a tiny lattice there are probably many many more sweeps done in the minimum time of the run than you specified.
Matthias
Dear João Lopes,
From: Matthias Troyer troyer@phys.ethz.ch Date: Thu, 28 Aug 2008 07:58:43 -0600
Please check in the output of the measurements how many measurements were actually done. For such a tiny lattice there are probably many many more sweeps done in the minimum time of the run than you specified.
FYI, you can restrict the total number of sweeps to SWEEPS specified in the paramter file by activating the line 159 in qmc/looper/path_integral.C :
// if (!mcs.can_work()) return;
which is commented out by factory default.
Synge
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