added fake _xdr attributes in case the trajectory was constructed by other means than reading a gromacs xtc file

src/mdevaluate/reader.py

@@ -23,6 +23,8 @@ from .logging_util import logger
 from . import atoms
 from .coordinates import Coordinates
 
+from unittest.mock import MagicMock
+
 CSR_ATTRS = ("data", "indices", "indptr")
 NOJUMP_MAGIC = 2016
 Group_RE = re.compile(r"\[ ([-+\w]+) \]")
@@ -240,7 +242,18 @@ def generate_nojump_matrices(trajectory: Coordinates):
     save_nojump_matrices(trajectory.frames)
 
 
+def _ensure_xdr(reader: BaseReader):
+    """Patch missing _xdr attribute for non-XDR readers (e.g. LAMMPS DumpReader)
+    with a stable mock so checksums are consistent across runs."""
+    if not hasattr(reader.rd, '_xdr'):
+        mock_xdr = MagicMock()
+        mock_xdr.offsets = np.arange(len(reader))
+        print(f"Adding mock _xdr attribute for to reader of length {len(reader)}.")
+        reader.rd._xdr = mock_xdr
+
+
 def save_nojump_matrices(reader: BaseReader, matrices: npt.ArrayLike = None):
+    _ensure_xdr(reader)
     if matrices is None:
         matrices = reader.nojump_matrices
     data = {"checksum": checksum(NOJUMP_MAGIC, checksum(reader))}
@@ -253,6 +266,7 @@ def save_nojump_matrices(reader: BaseReader, matrices: npt.ArrayLike = None):
 
 
 def load_nojump_matrices(reader: BaseReader):
+    _ensure_xdr(reader)
     zipname = nojump_load_filename(reader)
     try:
         data = np.load(zipname, allow_pickle=True)