io: fix netcdf IO for parameters

doc/release_notes.rst

@@ -4,6 +4,7 @@ Release Notes
 Upcoming Version
 ----------------
 
+* The writing and reading from netcdf files was fixed to correctly handle the model `parameters` field.
 
 Version 0.3.10
 --------------

linopy/io.py

@@ -918,7 +918,7 @@ def with_prefix(ds, prefix):
     if m.objective.value is not None:
         objective = objective.assign_attrs(value=m.objective.value)
     obj = [with_prefix(objective, "objective")]
-    params = [with_prefix(m.parameters, "params")]
+    params = [with_prefix(m.parameters, "parameters")]
 
     scalars = {k: getattr(m, k) for k in m.scalar_attrs}
     ds = xr.merge(vars + cons + obj + params, combine_attrs="drop_conflicts")
@@ -1008,7 +1008,7 @@ def get_prefix(ds, prefix):
     m.objective.sense = objective.attrs.pop("sense")
     m.objective._value = objective.attrs.pop("value", None)
 
-    m.parameters = get_prefix(ds, "parameter")
+    m.parameters = get_prefix(ds, "parameters")
 
     for k in m.scalar_attrs:
         setattr(m, k, ds.attrs.get(k))

linopy/solvers.py

@@ -49,9 +49,17 @@
 
     available_solvers.append("gurobi")
 with contextlib.suppress(ImportError):
+    _new_highspy_mps_layout = None
     import highspy
 
     available_solvers.append("highs")
+    from importlib.metadata import version
+
+    if version("highspy") < "1.7.1":
+        _new_highspy_mps_layout = False
+    else:
+        _new_highspy_mps_layout = True
+
 if sub.run([which, "glpsol"], stdout=sub.DEVNULL, stderr=sub.STDOUT).returncode == 0:
     available_solvers.append("glpk")
 
@@ -132,7 +140,7 @@ def maybe_adjust_objective_sign(solution, sense, io_api):
     if np.isnan(solution.objective):
         return
 
-    if io_api == "mps" and sys.version_info < (3, 12):
+    if io_api == "mps" and not _new_highspy_mps_layout:
         logger.info(
             "Adjusting objective sign due to switched coefficients in MPS file."
         )
@@ -180,9 +188,9 @@ def run_cbc(
         )
 
     # CBC does not like the OBJSENSE line in MPS files, which new highspy versions write
-    if io_api == "mps" and model.sense == "max" and sys.version_info >= (3, 12):
+    if io_api == "mps" and model.sense == "max" and _new_highspy_mps_layout:
         raise ValueError(
-            "GLPK does not support maximization in MPS format for Python 3.12+"
+            "CBC does not support maximization in MPS format highspy versions >=1.7.1"
         )
 
     problem_fn = model.to_file(problem_fn, io_api)
@@ -293,9 +301,9 @@ def run_glpk(
         )
 
     # GLPK does not like the OBJSENSE line in MPS files, which new highspy versions write
-    if io_api == "mps" and model.sense == "max" and sys.version_info >= (3, 12):
+    if io_api == "mps" and model.sense == "max" and _new_highspy_mps_layout:
         raise ValueError(
-            "GLPK does not support maximization in MPS format for Python 3.12+"
+            "GLPK does not support maximization in MPS format highspy versions >=1.7.1"
         )
 
     problem_fn = model.to_file(problem_fn, io_api)

pyproject.toml

@@ -61,7 +61,7 @@ dev = [
 solvers = [
     "gurobipy",
     "highspy>=1.5.0; python_version < '3.12'",
-    "highspy>=1.7.1.dev1; python_version >= '3.12'",
+    "highspy>=1.7.1; python_version >= '3.12'",
     "cplex; platform_system != 'Darwin' and python_version < '3.12'",
     "mosek",
     "mindoptpy; python_version < '3.12'",

test/test_io.py

@@ -25,6 +25,8 @@ def model():
 
     m.add_objective(2 * x + 3 * y)
 
+    m.parameters["param"] = xr.DataArray([1, 2, 3, 4], dims=["x"])
+
     return m
 
 

test/test_optimization.py

@@ -17,7 +17,7 @@
 from xarray.testing import assert_equal
 
 from linopy import GREATER_EQUAL, LESS_EQUAL, Model
-from linopy.solvers import available_solvers, quadratic_solvers
+from linopy.solvers import _new_highspy_mps_layout, available_solvers, quadratic_solvers
 
 logger = logging.getLogger(__name__)
 
@@ -389,7 +389,7 @@ def test_model_maximization(model_maximization, solver, io_api):
     assert m.objective.sense == "max"
     assert m.objective.value is None
 
-    if solver in ["cbc", "glpk"] and io_api == "mps" and sys.version_info >= (3, 12):
+    if solver in ["cbc", "glpk"] and io_api == "mps" and _new_highspy_mps_layout:
         with pytest.raises(ValueError):
             m.solve(solver, io_api=io_api)
     else: