Dear All. I would like to report a likely bug.
I play with a simple transverse ising model for S=1/2. I take a short chain of length say 8, compute magnetization in x and z direction. When I compute the same input with mps_optim and sparsediag i obtain different results. Both codes give me different magnetizatios in mps_optim measurement seems to be wrong by a factor.
I changed the definition of a default model “spin” (see below), the coupling is along x axis and field is along z. I consider the following input:
LATTICE="inhomogeneous chain lattice" MODEL_LIBRARY="models.xml"
MODEL="spin" J=1 SWEEPS=8 chkp_each=8
MEASURE_LOCAL[Local magnetization Xa]=Splus MEASURE_LOCAL[Local magnetization Xb]=Sminus MEASURE_LOCAL[Local magnetization X1]=Sx MEASURE_LOCAL[Local magnetization X2]=Sxx MEASURE_LOCAL[Local magnetization Z]=Sz MAXSTATES=40; NUMBER_EIGENVALUES=1;
{h=0;Gamma=0;L=8}
******************* In the above the Sxx operator is defined exactly the same as Sx: <SITEOPERATOR name="Sx" site="x"> 1/2*(Splus(x)+Sminus(x)) </SITEOPERATOR>
but with 1/4 factor, not 1/2: <SITEOPERATOR name="Sxx" site="x"> 1/4*(Splus(x)+Sminus(x)) </SITEOPERATOR>
There are 2 runs that are important for my message:
RUN A): running the above input with sparsediag gives (at any site): Local magnetization Xa=0.5 Local magnetization Xb=0.5 Local magnetization X1=0.5 Local magnetization X2=0.25
Which makes sense, as Sx=0.5*(Jplus + Jminus)
RUN B): running the above input with mps_optim gives (at any site): Local magnetization Xa=0.5 Local magnetization Xb=0.5 Local magnetization X1=1.0 Local magnetization X2=1.0
My conclusion: It seems that measurement ignores the factor 1/4 in the definition of Sxx and 1/2 in the definition of Sx. If it is indeed the case (not stupid mistake on my side), would it be possible to issue a patch?
If I change <BONDTERM source="i" target="j"> <PARAMETER name="J#" default="J"/> -J#*Sx(i)*Sx(j)*4 </BONDTERM>
into <BONDTERM source="i" target="j"> <PARAMETER name="J#" default="J"/> -J#*Sxx(i)*Sxx(j)*4 </BONDTERM>
then I get a correct factor 4 reduction in energy. So it seems only the mesurement ignores the numerical factor.
If I exchange x-z direction in the Hamiltonian everything seems fine.
Best, Mateusz Łącki
Dear Mateusz,
Which version of the code are you using? We recently rewrote how measurements are parsed (specially for measurement expressions).
Could you please try with a version newer than r7807?
Best, Michele
-- ETH Zurich Dr. Michele Dolfi Institute for Theoretical Physics HIT G 32.4 Wolfgang-Pauli-Str. 27 8093 Zurich Switzerland
dolfim@phys.ethz.ch www.itp.phys.ethz.ch
+41 44 633 78 56 phone +41 44 633 11 15 fax
On 14 Jan 2017, at 18:17, Mateusz Łącki mateusz.lacki@gmail.com wrote:
Dear All. I would like to report a likely bug.
I play with a simple transverse ising model for S=1/2. I take a short chain of length say 8, compute magnetization in x and z direction. When I compute the same input with mps_optim and sparsediag i obtain different results. Both codes give me different magnetizatios in mps_optim measurement seems to be wrong by a factor.
I changed the definition of a default model “spin” (see below), the coupling is along x axis and field is along z. I consider the following input:
LATTICE="inhomogeneous chain lattice" MODEL_LIBRARY="models.xml"
MODEL="spin" J=1 SWEEPS=8 chkp_each=8
MEASURE_LOCAL[Local magnetization Xa]=Splus MEASURE_LOCAL[Local magnetization Xb]=Sminus MEASURE_LOCAL[Local magnetization X1]=Sx MEASURE_LOCAL[Local magnetization X2]=Sxx MEASURE_LOCAL[Local magnetization Z]=Sz MAXSTATES=40; NUMBER_EIGENVALUES=1;
{h=0;Gamma=0;L=8}
In the above the Sxx operator is defined exactly the same as Sx:
<SITEOPERATOR name="Sx" site="x"> 1/2*(Splus(x)+Sminus(x)) </SITEOPERATOR>
but with 1/4 factor, not 1/2:
<SITEOPERATOR name="Sxx" site="x"> 1/4*(Splus(x)+Sminus(x)) </SITEOPERATOR>
There are 2 runs that are important for my message:
RUN A): running the above input with sparsediag gives (at any site): Local magnetization Xa=0.5 Local magnetization Xb=0.5 Local magnetization X1=0.5 Local magnetization X2=0.25
Which makes sense, as Sx=0.5*(Jplus + Jminus)
RUN B): running the above input with mps_optim gives (at any site): Local magnetization Xa=0.5 Local magnetization Xb=0.5 Local magnetization X1=1.0 Local magnetization X2=1.0
My conclusion: It seems that measurement ignores the factor 1/4 in the definition of Sxx and 1/2 in the definition of Sx. If it is indeed the case (not stupid mistake on my side), would it be possible to issue a patch?
If I change
<BONDTERM source="i" target="j"> <PARAMETER name="J#" default="J"/> -J#*Sx(i)*Sx(j)*4 </BONDTERM>
into
<BONDTERM source="i" target="j"> <PARAMETER name="J#" default="J"/> -J#*Sxx(i)*Sxx(j)*4 </BONDTERM>
then I get a correct factor 4 reduction in energy. So it seems only the mesurement ignores the numerical factor.
If I exchange x-z direction in the Hamiltonian everything seems fine.
Best, Mateusz Łącki
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Hi Mateusz,
I didn’t manage to follow up on this earlier. Could you please send the model file that you are using?
Michele
-- ETH Zurich Dr. Michele Dolfi Institute for Theoretical Physics HIT G 32.4 Wolfgang-Pauli-Str. 27 8093 Zurich Switzerland
dolfim@phys.ethz.ch www.itp.phys.ethz.ch
+41 44 633 78 56 phone +41 44 633 11 15 fax
On Jan 15, 2017, at 12:28 PM, Michele Dolfi dolfim@phys.ethz.ch wrote:
Dear Mateusz,
Which version of the code are you using? We recently rewrote how measurements are parsed (specially for measurement expressions).
Could you please try with a version newer than r7807?
Best, Michele
-- ETH Zurich Dr. Michele Dolfi Institute for Theoretical Physics HIT G 32.4 Wolfgang-Pauli-Str. 27 8093 Zurich Switzerland
dolfim@phys.ethz.ch mailto:dolfim@phys.ethz.ch www.itp.phys.ethz.ch http://www.itp.phys.ethz.ch/
+41 44 633 78 56 phone +41 44 633 11 15 fax
On 14 Jan 2017, at 18:17, Mateusz Łącki <mateusz.lacki@gmail.com mailto:mateusz.lacki@gmail.com> wrote:
Dear All. I would like to report a likely bug.
I play with a simple transverse ising model for S=1/2. I take a short chain of length say 8, compute magnetization in x and z direction. When I compute the same input with mps_optim and sparsediag i obtain different results. Both codes give me different magnetizatios in mps_optim measurement seems to be wrong by a factor.
I changed the definition of a default model “spin” (see below), the coupling is along x axis and field is along z. I consider the following input:
LATTICE="inhomogeneous chain lattice" MODEL_LIBRARY="models.xml"
MODEL="spin" J=1 SWEEPS=8 chkp_each=8
MEASURE_LOCAL[Local magnetization Xa]=Splus MEASURE_LOCAL[Local magnetization Xb]=Sminus MEASURE_LOCAL[Local magnetization X1]=Sx MEASURE_LOCAL[Local magnetization X2]=Sxx MEASURE_LOCAL[Local magnetization Z]=Sz MAXSTATES=40; NUMBER_EIGENVALUES=1;
{h=0;Gamma=0;L=8}
In the above the Sxx operator is defined exactly the same as Sx:
<SITEOPERATOR name="Sx" site="x"> 1/2*(Splus(x)+Sminus(x)) </SITEOPERATOR>
but with 1/4 factor, not 1/2:
<SITEOPERATOR name="Sxx" site="x"> 1/4*(Splus(x)+Sminus(x)) </SITEOPERATOR>
There are 2 runs that are important for my message:
RUN A): running the above input with sparsediag gives (at any site): Local magnetization Xa=0.5 Local magnetization Xb=0.5 Local magnetization X1=0.5 Local magnetization X2=0.25
Which makes sense, as Sx=0.5*(Jplus + Jminus)
RUN B): running the above input with mps_optim gives (at any site): Local magnetization Xa=0.5 Local magnetization Xb=0.5 Local magnetization X1=1.0 Local magnetization X2=1.0
My conclusion: It seems that measurement ignores the factor 1/4 in the definition of Sxx and 1/2 in the definition of Sx. If it is indeed the case (not stupid mistake on my side), would it be possible to issue a patch?
If I change
<BONDTERM source="i" target="j"> <PARAMETER name="J#" default="J"/> -J#*Sx(i)*Sx(j)*4 </BONDTERM>
into
<BONDTERM source="i" target="j"> <PARAMETER name="J#" default="J"/> -J#*Sxx(i)*Sxx(j)*4 </BONDTERM>
then I get a correct factor 4 reduction in energy. So it seems only the mesurement ignores the numerical factor.
If I exchange x-z direction in the Hamiltonian everything seems fine.
Best, Mateusz Łącki
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I have tried out using DMRG with an infinite lattice. I could not find any information about how to do infinite DMRG so I just assumed that I could define an infinite lattice graph and work with that.... However when I try this I get the error: "bad lexical cast: source type value could not be interpreted as target". This was for a 1d lattice graph of one site with one unit cell and the spin model. I have included the files I used along with this email just in case...
Is this the correct way to approach this or is there any other way to get out iDMRG calculations??
Best
/Axel
PhD Student
Stockholm University
Dear Axel,
Infinite systems are not supported in the current ALPS applications.
However some people in our group worked on infinite algorithm based on ALPS.
For example high temperature series expansion as well as perturbative series expansion by Andreas Hehn. http://dx.doi.org/10.1016/j.cpc.2016.09.003 http://dx.doi.org/10.1016/j.cpc.2016.09.003
For infinite MPS there is also some work by Juan Osorio.
Best regards, Michele
-- ETH Zurich Dr. Michele Dolfi Institute for Theoretical Physics HIT G 32.4 Wolfgang-Pauli-Str. 27 8093 Zurich Switzerland
dolfim@phys.ethz.ch www.itp.phys.ethz.ch
+41 44 633 78 56 phone +41 44 633 11 15 fax
On 18 Jan 2017, at 18:16, Axel Gagge axel.gagge@fysik.su.se wrote:
I have tried out using DMRG with an infinite lattice. I could not find any information about how to do infinite DMRG so I just assumed that I could define an infinite lattice graph and work with that.... However when I try this I get the error: "bad lexical cast: source type value could not be interpreted as target". This was for a 1d lattice graph of one site with one unit cell and the spin model. I have included the files I used along with this email just in case...
Is this the correct way to approach this or is there any other way to get out iDMRG calculations?
Best /Axel PhD Student Stockholm University <my_models.xml><my_lattices.xml><Test of iDMRG.ipynb>
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As a side note. We recently published a new version of the dmrg codes which are more flexible and faster. http://dx.doi.org/10.1016/j.cpc.2014.08.019 http://dx.doi.org/10.1016/j.cpc.2014.08.019
Best, Michele
-- ETH Zurich Dr. Michele Dolfi Institute for Theoretical Physics HIT G 32.4 Wolfgang-Pauli-Str. 27 8093 Zurich Switzerland
dolfim@phys.ethz.ch www.itp.phys.ethz.ch
+41 44 633 78 56 phone +41 44 633 11 15 fax
On 18 Jan 2017, at 20:35, Michele Dolfi dolfim@phys.ethz.ch wrote:
Dear Axel,
Infinite systems are not supported in the current ALPS applications.
However some people in our group worked on infinite algorithm based on ALPS.
For example high temperature series expansion as well as perturbative series expansion by Andreas Hehn. http://dx.doi.org/10.1016/j.cpc.2016.09.003 http://dx.doi.org/10.1016/j.cpc.2016.09.003
For infinite MPS there is also some work by Juan Osorio.
Best regards, Michele
-- ETH Zurich Dr. Michele Dolfi Institute for Theoretical Physics HIT G 32.4 Wolfgang-Pauli-Str. 27 8093 Zurich Switzerland
dolfim@phys.ethz.ch mailto:dolfim@phys.ethz.ch www.itp.phys.ethz.ch http://www.itp.phys.ethz.ch/
+41 44 633 78 56 phone +41 44 633 11 15 fax
On 18 Jan 2017, at 18:16, Axel Gagge <axel.gagge@fysik.su.se mailto:axel.gagge@fysik.su.se> wrote:
I have tried out using DMRG with an infinite lattice. I could not find any information about how to do infinite DMRG so I just assumed that I could define an infinite lattice graph and work with that.... However when I try this I get the error: "bad lexical cast: source type value could not be interpreted as target". This was for a 1d lattice graph of one site with one unit cell and the spin model. I have included the files I used along with this email just in case...
Is this the correct way to approach this or is there any other way to get out iDMRG calculations?
Best /Axel PhD Student Stockholm University <my_models.xml><my_lattices.xml><Test of iDMRG.ipynb>
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Thank you. My idea was to use it to find critical exponents of my models though finite entanglement/bond dimension scaling at the quantum critical point, but I can find ways around it as you do in the paper...
Many thanks,
Axel
________________________________ Från: Comp-phys-alps-users comp-phys-alps-users-bounces@lists.phys.ethz.ch för Michele Dolfi dolfim@phys.ethz.ch Skickat: den 18 januari 2017 20:38 Till: comp-phys-alps-users@lists.phys.ethz.ch Ämne: Re: [ALPS-users] Question about iDMRG in ALPS
As a side note. We recently published a new version of the dmrg codes which are more flexible and faster. http://dx.doi.org/10.1016/j.cpc.2014.08.019
Best, Michele
-- ETH Zurich Dr. Michele Dolfi Institute for Theoretical Physics HIT G 32.4 Wolfgang-Pauli-Str. 27 8093 Zurich Switzerland
dolfim@phys.ethz.chmailto:dolfim@phys.ethz.ch www.itp.phys.ethz.chhttp://www.itp.phys.ethz.ch
+41 44 633 78 56 phone +41 44 633 11 15 fax
On 18 Jan 2017, at 20:35, Michele Dolfi <dolfim@phys.ethz.chmailto:dolfim@phys.ethz.ch> wrote:
Dear Axel,
Infinite systems are not supported in the current ALPS applications.
However some people in our group worked on infinite algorithm based on ALPS.
For example high temperature series expansion as well as perturbative series expansion by Andreas Hehn. http://dx.doi.org/10.1016/j.cpc.2016.09.003
For infinite MPS there is also some work by Juan Osorio.
Best regards, Michele
-- ETH Zurich Dr. Michele Dolfi Institute for Theoretical Physics HIT G 32.4 Wolfgang-Pauli-Str. 27 8093 Zurich Switzerland
dolfim@phys.ethz.chmailto:dolfim@phys.ethz.ch www.itp.phys.ethz.chhttp://www.itp.phys.ethz.ch/
+41 44 633 78 56 phone +41 44 633 11 15 fax
On 18 Jan 2017, at 18:16, Axel Gagge <axel.gagge@fysik.su.semailto:axel.gagge@fysik.su.se> wrote:
I have tried out using DMRG with an infinite lattice. I could not find any information about how to do infinite DMRG so I just assumed that I could define an infinite lattice graph and work with that.... However when I try this I get the error: "bad lexical cast: source type value could not be interpreted as target". This was for a 1d lattice graph of one site with one unit cell and the spin model. I have included the files I used along with this email just in case...
Is this the correct way to approach this or is there any other way to get out iDMRG calculations??
Best /Axel PhD Student Stockholm University <my_models.xml><my_lattices.xml><Test of iDMRG.ipynb>
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