DX,DY misalingments are not properly assigned to sliced elements

[roman-martin]

The following example assumes #34 is fixed:

import cpymad.madx
import pysixtrack

# code from help(pysixtrack.Line.apply_madx_errors) with minimal madx sequence
madx = cpymad.madx.Madx()
madx.input('''
    !----EXAMPLE----------------------------------------------------------------
    MQ1: Quadrupole, K1:=KQ1, L=1.0;
    MQ2: Quadrupole, K1:=KQ2, L=1.0;

    KQ1 = 0.02;
    KQ2 = -0.02;

    testseq: SEQUENCE, l = 20.0;
        MQ1, at = 5;
        MQ2, at=18;
    ENDSEQUENCE;

    !---the usual stuff
    BEAM, PARTICLE=PROTON, ENERGY=7000.0, EXN=2.2e-6, EYN=2.2e-6;
    USE, SEQUENCE=testseq;

    Select, flag=makethin, pattern="MQ1", slice=2;
    makethin, sequence=testseq;

    use, sequence=testseq;

    !---misalign collimator
    select, flag = error, clear;
    select, flag = error, pattern = "MQ1";
    ealign, dx :=  0.01, dy :=0.01;
    select, flag = error, clear;
    select, flag = error, pattern = "MQ2";
    ealign, dx :=  0.02, dy :=0.02;
    select, flag = error, full;

    !---/EXAMPLE----------------------------------------------------------------
''')
seq = madx.sequence.testseq
madx.command.esave(file='lattice_errors.err')
madx.command.readtable(file='lattice_errors.err', table="errors")
errors = madx.table.errors
pysixtrack_line = pysixtrack.Line.from_madx_sequence(seq, install_apertures=True)
pysixtrack_line.apply_madx_errors(errors)

print('\n')
print('Line content:')
for name,element in zip(pysixtrack_line.element_names,pysixtrack_line.elements):
    print("{0:30} : {1}".format(name,element))

The example generates a MAD-X sequence with misaligned quadrupoles and transfers everything to pysixtrack. In the end it outputs the line (element_names and elements). MQ1 is sliced into multiple slices, MQ2 is a single multipole.

You can see that the DX and DY misalignments of the multi-slice quadrupole are assigned to the start marker and twice to the first slice while the single slice quadrupole is misaligned properly.

[roman-martin]

I looked a little into this and the problem seems to be the use of elementvs element_name apply_madx_errors(): element_name -> element add_offset_error_to(element): element -> idx_el However, the intermittent element is not unique for slices and any kind of marker, so the first marker gets every offset for markers the first multipole slice gets every offset for similar multipoles, etc.

[aoeftiger]

fixed by PR #37 , follow-up discussion how to handle general multiple occurrences of the same name posted as a new issue: https://github.com/SixTrack/pysixtrack/issues/52