How to get the green function result from Worm algorithm?

[LAZY1764]

To estimate the energy gap and the correlation length, I need the Green's function result. I have set the parameter 'MEASURE_GREEN' : True (as the alps documentation write ), but finally find no Green's function data in the ObservableList.

for L in [10,20,40]:
    for t in np.linspace(0.05,0.07,12):
        beta = 50.0*L/10
        parms.append({ 
        'LATTICE'        : "square lattice",  
        'L'              : L, 
        'MODEL'          : "boson Hubbard",  
        't'              : t,     
        'U'              : 1.0,     
        'mu'             : mu, 
        'T'              : 1.0/beta,   
        'THERMALIZATION' : 6000,   
        'SWEEPS'         : 30000,     
        'Nmax'           : 4,     
        'SKIP'           : 50,      
        'MEASURE_GREEN'  : True
    })
#...
pyalps.runApplication('worm', input_file)
#...
result_files = pyalps.getResultFiles(prefix="testGREEN_20260324_2125")
observables = ['Stiffness', 'Density^2','Density','Green’s function']
data = pyalps.loadMeasurements(result_files, observables)

[egull]

@vws100 will you have a look again?

[vws100]

Yes, the worm code documentation mentions the "MEASURE_GREEN" flag. The documentation also says:

"flag that indicates whether the Green’s function should be measured. Don’t use - this is untested!"

@LodePollet Thoughts on testing MEASURE_GREEN?

[LodePollet]

we never had time-dependent measurements of the Green function in ALPS. For equal-time measurements I consider it unsafe to use "dwa".
If you are willing to use the worm code from https://github.com/LodePollet/worm then I can guarantee the equal-time measurements and there is enough code provided to also get access to imaginary time-dependent measurements.
For the ALPS "worm" application, I see that the measurement of the green function is commented out. I cannot say anything about that; I don't know what the issue is there.

[LAZY1764]

@LodePollet Thank you for the clarification! I will use the worm code from your repository as suggested.