Add gulp test example, and hopefully fix gulp conformer rounding error.

.gitignore

@@ -15,4 +15,7 @@ docs/source/_autosummary
 # Some folders get created by tests.
 **/tests_output
 docs/build
-tests/failures.txt
+tests/failures.txt
+
+/examples/gulp_test_output/
+/examples/gulp_test_output_MD/

examples/gulp_test_example.py

@@ -0,0 +1,100 @@
+import glob
+import logging
+import os
+import sys
+
+import stk
+import stko
+
+
+def main():
+    first_line = f"Usage: {__file__}.py"
+    if not len(sys.argv) == 2:
+        logging.info(f"{first_line} gulp_path")
+        sys.exit()
+    else:
+        gulp_path = sys.argv[1]
+
+    bb1 = stk.BuildingBlock(
+        smiles="[Cu+2]",
+        functional_groups=(
+            stk.SingleAtom(stk.Cu(0, charge=2)) for i in range(4)
+        ),
+        position_matrix=([0, 0, 0],),
+    )
+    bb2 = stk.BuildingBlock(
+        smiles="O=C(O)c1ccc(Br)cc1",
+        functional_groups=[
+            stk.SmartsFunctionalGroupFactory(
+                smarts="[#6]~[#8]~[#1]",
+                bonders=(1,),
+                deleters=(2,),
+            ),
+            stk.SmartsFunctionalGroupFactory(
+                smarts="[#6]~[#8X1]",
+                bonders=(1,),
+                deleters=(),
+            ),
+        ],
+    )
+    structure = stk.ConstructedMolecule(
+        topology_graph=stk.metal_complex.Paddlewheel(
+            metals=bb1,
+            ligands=bb2,
+            reaction_factory=stk.DativeReactionFactory(
+                stk.GenericReactionFactory(
+                    bond_orders={
+                        frozenset(
+                            {
+                                stk.GenericFunctionalGroup,
+                                stk.SingleAtom,
+                            }
+                        ): 9,
+                    },
+                ),
+            ),
+        ),
+    )
+
+    # Perform Gulp optimisation with UFF4MOF.
+    # Use conjugate gradient method for a slower, but more stable
+    # optimisation.
+    gulp_opt = stko.GulpUFFOptimizer(
+        gulp_path=gulp_path,
+        output_dir="gulp_test_output",
+        metal_FF={29: "Cu4+2"},
+        conjugate_gradient=True,
+        maxcyc=500,
+    )
+    # Assign the force field.
+    gulp_opt.assign_FF(structure)
+    # Run optimization.
+    structure = gulp_opt.optimize(mol=structure)
+    structure.write(os.path.join("gulp_test_output", "opt_structure.mol"))
+
+    target_num_confs = 40
+    gulp_MD = stko.GulpUFFMDOptimizer(
+        gulp_path=gulp_path,
+        metal_FF={29: "Cu4+2"},
+        output_dir="gulp_test_output_MD",
+        temperature=300,
+        equilbration=0.2,
+        production=67.9,
+        N_conformers=target_num_confs,
+        opt_conformers=False,
+        save_conformers=True,
+    )
+    gulp_MD.assign_FF(structure)
+    structure = gulp_MD.optimize(structure)
+    structure.write(os.path.join("gulp_test_output_MD", "opt_structure.mol"))
+
+    confs_gen = glob.glob("gulp_test_output_MD/conf*.xyz")
+    assert len(confs_gen) == target_num_confs
+
+
+if __name__ == "__main__":
+    logging.basicConfig(
+        level=logging.INFO,
+        format="%(asctime)s | %(levelname)s | %(message)s",
+    )
+    main()

src/stko/optimizers/gulp.py

@@ -7,6 +7,7 @@
 """
 
 import logging
+import math
 import os
 import re
 import shutil
@@ -919,6 +920,7 @@ def __init__(
         self._timestep = timestep
         self._N_conformers = N_conformers
         samples = float(self._production) / float(self._N_conformers)
+        samples = math.floor(samples * 1000) / 1000
         self._sample = samples
         self._write = samples
         self._opt_conformers = opt_conformers

src/stko/optimizers/rdkit.py

@@ -10,6 +10,7 @@
 import numpy as np
 import rdkit.Chem.AllChem as rdkit
 import stk
+
 from stko.optimizers.optimizers import Optimizer
 from stko.optimizers.utilities import (
     get_metal_atoms,