Backend paddle: switch default line_search_fn of L-BFGS to 'strong_wolfe' (#1790)

Author: lijialin03

deepxde/model.py

@@ -777,7 +777,7 @@ def _train_pytorch_lbfgs(self):
             )
 
             n_iter = self.opt.state_dict()["state"][0]["n_iter"]
-            if prev_n_iter == n_iter:
+            if prev_n_iter == n_iter - 1:
                 # Converged
                 break
 
@@ -809,7 +809,7 @@ def _train_paddle_lbfgs(self):
             )
 
             n_iter = self.opt.state_dict()["state"]["n_iter"]
-            if prev_n_iter == n_iter:
+            if prev_n_iter == n_iter - 1:
                 # Converged
                 break
 

deepxde/optimizers/paddle/optimizers.py

@@ -34,7 +34,7 @@ def get(params, optimizer, learning_rate=None, decay=None):
             tolerance_grad=LBFGS_options["gtol"],
             tolerance_change=LBFGS_options["ftol"],
             history_size=LBFGS_options["maxcor"],
-            line_search_fn=None,
+            line_search_fn=("strong_wolfe" if LBFGS_options["maxls"] > 0 else None),
             parameters=params,
         )
         return optim