write initial and final structure if save_full is false

src/fairchem/core/common/relaxation/optimizers/lbfgs_torch.py

@@ -92,14 +92,17 @@ def run(self, fmax, steps):
         iteration = 0
         max_forces = self.optimizable.get_max_forces(apply_constraint=True)
         logging.info("Step   Fmax(eV/A)")
+
         while iteration < steps and not self.optimizable.converged(
             forces=None, fmax=self.fmax, max_forces=max_forces
         ):
             logging.info(
                 f"{iteration} " + " ".join(f"{x:0.3f}" for x in max_forces.tolist())
             )
 
-            if self.trajectories is not None and self.save_full is True:
+            if self.trajectories is not None and (
+                self.save_full is True or iteration == 0
+            ):
                 self.write()
 
             self.step(iteration)

tests/core/common/test_lbfgs_torch.py

@@ -53,7 +53,9 @@ def test_lbfgs_write_trajectory(save_full_traj, steps, batch, calculator, tmp_pa
     traj_files = list(tmp_path.glob("*.traj"))
     assert len(traj_files) == len(batch)
 
-    traj_length = 0 if steps == 0 else steps + 1 if save_full_traj else 1
+    traj_length = (
+        0 if steps == 0 else steps + 1 if save_full_traj else 2
+    )  # first and final frame
     for file in traj_files:
         traj = read(file, ":")
         assert len(traj) == traj_length