[ALPS-users] Questions about MEASURE_LOCAL_AT in MPS-DMRG

[Michele Dolfi]

Hello,

> Q1: Are the indices, (i_11, ...i_1n), the vertex ids or vertex coordinates or the index of the vertex in some array, or sth else?

They are correspond to the sequential index of the lattice vertexes.
The best way to understand the sequence is by using the “printgraph” application.


> Q2: I understand that the restriction i_1 < i_2 < i_3 ... is probably there to simplify the MPS contraction but is there a simple way to go around it?

I would suggest to make a script to generate all the different measurements.
You could put them in the same parameter file, but usually I suggest to make different runs, such that you can launch all in parallel on a cluster.


> Q3: There is no limit on the number of measurement or the number of operators that can be defined, right?


No, I don’t think there is an actual limit, if not the memory that they will require.


Best,
Michele



> On 22 Nov 2017, at 20:38, Amir M.Aghaei <amir.maghaei at gmail.com> wrote:
> 
> Hi,
> 
> This is the documentation for 'MEASURE_LOCAL_AT'
> 
> MEASURE_LOCAL_AT[NAME] 
> Syntax for the value:
> 
> Defines a new measurement called NAME where the sequence of operators op_1:...:op_n is applied to all tuples of indices (of length n like the number of operators) listed after the vertical bar symbol.
> 
> I have three question:
> 
> Q1: Are the indices, (i_11, ...i_1n), the vertex ids or vertex coordinates or the index of the vertex in some array, or sth else?
> 
> Q2: I understand that the restriction i_1 < i_2 < i_3 ... is probably there to simplify the MPS contraction but is there a simple way to go around it?
> 
> Q3: There is no limit on the number of measurement or the number of operators that can be defined, right?
> 
> Amir
> 
> 
> 
> 
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