diff --git a/.github/workflows/pip.yml b/.github/workflows/pip.yml
index 093b4c06..e1d17107 100644
--- a/.github/workflows/pip.yml
+++ b/.github/workflows/pip.yml
@@ -93,8 +93,11 @@ jobs:
           kh-samples sklearn -i khiops_classifier -e
 
           # Test that the line containing "MPI command" also contains
-          # "mpiexec", which means that `mpiexec` has been found
-          kh-status | grep "MPI command" | grep -wq mpiexec
+          # an executable name under a /bin directory
+          # Note: this executable name can be different, depending on the MPI
+          # backend and OS; for instance, "orterun" for OpenMPI on Ubuntu Linux, but
+          # "mpiexec" for OpenMPI on Rocky Linux
+          kh-status | grep "MPI command" | grep -Ewq "(/.+?)/bin/.+"
   release:
     if: github.ref_type == 'tag'
     needs: [build, test]
diff --git a/.github/workflows/unit-tests.yml b/.github/workflows/unit-tests.yml
index a4341b25..cc9a2382 100644
--- a/.github/workflows/unit-tests.yml
+++ b/.github/workflows/unit-tests.yml
@@ -99,6 +99,9 @@ jobs:
           OMPI_MCA_rmaps_base_oversubscribe: true
           PRTE_MCA_rmaps_default_mapping_policy: :oversubscribe
         run: |
+          # Make sure '/bin' is before '/usr/bin' in PATH
+          PATH=$(echo "/bin:"$PATH | sed 's#:/bin##')
+
           # This is needed so that the Git tag is parsed and the khiops-python
           # version is retrieved
           git config --global --add safe.directory $(realpath .)
@@ -177,6 +180,9 @@ jobs:
           # Force > 2 CPU cores to launch mpiexec
           KHIOPS_PROC_NUMBER: 4
         run: |-
+          # Make sure '/bin' is before '/usr/bin' in PATH
+          PATH=$(echo "/bin:"$PATH | sed 's#:/bin##')
+
           # Make sure MPI support is not loaded through env modules
           # Note: As Docker container's shell is non-interactive, environment
           # modules are currently not initializing the shell anyway
diff --git a/khiops/core/internals/runner.py b/khiops/core/internals/runner.py
index d8681a00..28cb30e7 100644
--- a/khiops/core/internals/runner.py
+++ b/khiops/core/internals/runner.py
@@ -1146,8 +1146,12 @@ def _initialize_mpi_command_args(self):
         installation_method = _infer_khiops_installation_method()
         # In Conda-based, but non-Conda environment, specify mpiexec path
         if installation_method == "conda-based":
-            mpiexec_path = os.environ.get("KHIOPS_MPIEXEC_PATH") or os.path.join(
-                _infer_env_bin_dir_for_conda_based_installations(), "mpiexec"
+            # Python `os.path.realpath` resolves symlinks recursively, like GNU
+            # `readlink -f`; Python `os.readlink` does not
+            mpiexec_path = os.environ.get("KHIOPS_MPIEXEC_PATH") or os.path.realpath(
+                os.path.join(
+                    _infer_env_bin_dir_for_conda_based_installations(), "mpiexec"
+                )
             )
             if platform.system() == "Windows" and not os.path.splitext(mpiexec_path):
                 mpiexec_path += ".exe"
@@ -1165,8 +1169,11 @@ def _initialize_mpi_command_args(self):
                     )
         # In Conda or local installations, expect mpiexec in the PATH
         else:
-            mpiexec_path = os.environ.get("KHIOPS_MPIEXEC_PATH") or shutil.which(
-                "mpiexec"
+            link_to_mpiexec = shutil.which("mpiexec")
+            mpiexec_path = (
+                os.environ.get("KHIOPS_MPIEXEC_PATH")
+                or link_to_mpiexec
+                and os.path.realpath(link_to_mpiexec)
             )
         # If mpiexec is not in the path, and the installation method is local,
         # then try to load MPI environment module so that mpiexec is in the path
diff --git a/khiops/sklearn/tables.py b/khiops/sklearn/tables.py
index 331d1a02..b4709671 100644
--- a/khiops/sklearn/tables.py
+++ b/khiops/sklearn/tables.py
@@ -1441,32 +1441,23 @@ def _write_sparse_block(self, row_index, stream, target=None):
             assert target in self.target_column, "'target' must be in the target column"
             stream.write(f"{target}\t")
         row = self.matrix.getrow(row_index)
-        # Empty row in the sparse matrix: use the first variable as missing data
-        # TODO: remove this part once Khiops bug
-        # https://github.com/KhiopsML/khiops/issues/235 is solved
-        if row.size == 0:
-            for variable_index in self.column_ids:
-                stream.write(f"{variable_index + 1}: ")
-                break
-        # Non-empty row in the sparse matrix: get non-missing data
-        else:
-            # Variable indices are not always sorted in `row.indices`
-            # Khiops needs variable indices to be sorted
-            sorted_indices = np.sort(row.nonzero()[1], axis=-1, kind="mergesort")
-
-            # Flatten row for Python < 3.9 scipy.sparse.lil_matrix whose API
-            # is not homogeneous with other sparse matrices: it stores
-            # opaque Python lists as elements
-            # Thus:
-            # - if isinstance(self.matrix, sp.lil_matrix) and Python 3.8, then
-            # row.data is np.array([list([...])])
-            # - else, row.data is np.array([...])
-            # TODO: remove this flattening once Python 3.8 support is dropped
-            sorted_data = np.fromiter(self._flatten(row.data), row.data.dtype)[
-                sorted_indices.argsort()
-            ]
-            for variable_index, variable_value in zip(sorted_indices, sorted_data):
-                stream.write(f"{variable_index + 1}:{variable_value} ")
+        # Variable indices are not always sorted in `row.indices`
+        # Khiops needs variable indices to be sorted
+        sorted_indices = np.sort(row.nonzero()[1], axis=-1, kind="mergesort")
+
+        # Flatten row for Python < 3.9 scipy.sparse.lil_matrix whose API
+        # is not homogeneous with other sparse matrices: it stores
+        # opaque Python lists as elements
+        # Thus:
+        # - if isinstance(self.matrix, sp.lil_matrix) and Python 3.8, then
+        # row.data is np.array([list([...])])
+        # - else, row.data is np.array([...])
+        # TODO: remove this flattening once Python 3.8 support is dropped
+        sorted_data = np.fromiter(self._flatten(row.data), row.data.dtype)[
+            sorted_indices.argsort()
+        ]
+        for variable_index, variable_value in zip(sorted_indices, sorted_data):
+            stream.write(f"{variable_index + 1}:{variable_value} ")
         stream.write("\n")
 
     def create_table_file_for_khiops(self, output_dir, sort=True):
diff --git a/tests/test_dataset_class.py b/tests/test_dataset_class.py
index 9fff03cb..3a0d417f 100644
--- a/tests/test_dataset_class.py
+++ b/tests/test_dataset_class.py
@@ -565,13 +565,15 @@ def _load_khiops_sparse_file(self, stream):
             target, features = line.split(b"\t")
             feature_row = np.zeros(100)
             for feature in features.strip().split(b" "):
-                feature_index, feature_value = feature.split(b":")
-                try:
-                    feature_value = float(feature_value)
-                # missing value, whence empty string
-                except ValueError:
-                    feature_value = 0.0
-                feature_row[int(feature_index) - 1] = feature_value
+                indexed_feature = feature.split(b":")
+
+                # Skip missing feature
+                if len(indexed_feature) < 2:
+                    continue
+
+                # Set feature value in row at the specified index
+                feature_index, feature_value = indexed_feature
+                feature_row[int(feature_index) - 1] = float(feature_value)
             feature_matrix.append(feature_row)
             target_vector.append(float(target))
         target_array = np.array(target_vector)