Make ORCA executable path an explicit option.

README.md

@@ -106,11 +106,12 @@ emle-server --backend torchani
 
 (The default backend is `torchani`.)
 
-When using the `orca` backend, you will need to ensure that the _fake_ `orca`
-executable takes precedence in the `PATH`. (To check that EMLE is running,
-look for an `emle_log.txt` file in the working directory, where. The input
-for `orca` will be taken from the `&orc` section of the `sander` configuration
-file, so use this to specify the method, etc.
+When using the `orca` backend, you will also need to specify the path to the
+*real* `orca` exectubale using the `--orca-path` command-line argument, or the
+`EMLE_ORCA_PATH` environment variable. (To check that EMLE is running, look for
+an `emle_log.txt` file in the working directory, where. The input for `orca` will
+be taken from the `&orc` section of the `sander` configuration file, so use this
+to specify the method, etc.
 
 When using `deepmd` as the backend you will also need to specify a model
 file to use. This can be passed with the `--deepmd-model` command-line argument,

bin/emle-server

@@ -89,6 +89,7 @@ except:
     interpolate_steps = None
 qm_indices = os.getenv("EMLE_QM_INDICES")
 sqm_theory = os.getenv("EMLE_SQM_THEORY")
+orca_path = os.getenv("EMLE_ORCA_PATH")
 try:
     restart = strtobool(os.getenv("EMLE_RESTART"))
 except:
@@ -127,6 +128,7 @@ env = {
     "parm7": parm7,
     "qm_indices": qm_indices,
     "sqm_theory": sqm_theory,
+    "orca_path": orca_path,
     "restart": restart,
     "orca_template": orca_template,
     "log": log,
@@ -255,6 +257,12 @@ parser.add_argument(
     help="the semi-empirical theory to use for the QM region when using the SQM backend",
     required=False,
 )
+parser.add_argument(
+    "--orca-path",
+    type=str,
+    help="the path to the ORCA executable (required when using the ORCA backend)",
+    required=False,
+)
 parser.add_argument(
     "--restart",
     action=argparse.BooleanOptionalAction,

emle/calculator.py

@@ -377,6 +377,7 @@ def __init__(
         rascal_model=None,
         parm7=None,
         qm_indices=None,
+        orca_path=None,
         sqm_theory="DFTB3",
         lambda_interpolate=None,
         interpolate_steps=None,
@@ -455,6 +456,10 @@ def __init__(
             can be specified. The file should contain a single column with the
             indices being zero-based.
 
+        orca_path : str
+            The path to the ORCA executable. This is required when using the ORCA
+            backend.
+
         sqm_theory : str
             The QM theory to use when using the SQM backend. See the AmberTools
             manual for the supported theory levels for your version of AmberTools.
@@ -943,23 +948,19 @@ def __init__(
 
         # If the backend is ORCA, then try to find the executable.
         elif self._backend == "orca":
-            # Get the PATH for the environment.
-            path = _os.environ["PATH"]
+            if orca_path is None:
+                raise ValueError("'orca_path' must be specified when using the ORCA backend")
+
+            if not isinstance(orca_path, str):
+                raise TypeError("'orca_path' must be of type 'str'")
 
-            # Search the PATH for a matching executable, ignoring any conda
-            # directories.
+            # Convert to an absolute path.
+            abs_orca_path = _os.path.abspath(orca_path)
 
-            exes = []
-            for p in path.split(":"):
-                exe = _shutil.which("orca", path=p)
-                if exe and not ("conda" in exe or "mamba" in exe or "miniforge" in exe):
-                    exes.append(exe)
+            if not _os.path.isfile(abs_orca_path):
+                raise IOError(f"Unable to locate ORCA executable: '{orca_path}'")
 
-            # Use the first executable.
-            if len(exes) > 0:
-                self._orca_exe = exes[0]
-            else:
-                raise OSError("Couldn't find ORCA executable for in vacuo backend!")
+            self._orca_path = abs_orca_path
 
         # Initialise the maximum number of MM atom that have been seen.
         self._max_mm_atoms = 0
@@ -984,6 +985,7 @@ def __init__(
             "rascal_model": rascal_model,
             "parm7": parm7,
             "qm_indices": None if qm_indices is None else self._qm_indices,
+            "orca_path": orca_path,
             "sqm_theory": sqm_theory,
             "lambda_interpolate": lambda_interpolate,
             "interpolate_steps": interpolate_steps,
@@ -2577,7 +2579,7 @@ def _run_orca(
                 _shutil.move(xyz_file_qm, xyz_name)
 
             # Create the ORCA command.
-            command = f"{self._orca_exe} {inp_name}"
+            command = f"{self._orca_path} {inp_name}"
 
             # Run the command as a sub-process.
             proc = _subprocess.run(