update examples

examples/run_first_order_ode.py

@@ -0,0 +1,42 @@
+import argparse
+
+from torch.nn import Softplus
+
+from pina.model import FeedForward
+from pina import Plotter, PINN
+from problems.first_order_ode import FirstOrderODE
+
+
+if __name__ == "__main__":
+
+    parser = argparse.ArgumentParser(description="Run PINA")
+    group = parser.add_mutually_exclusive_group(required=True)
+    group.add_argument("-s", "-save", action="store_true")
+    group.add_argument("-l", "-load", action="store_true")
+    parser.add_argument("id_run", help="number of run", type=int)
+    args = parser.parse_args()
+
+    # define Problem + Model + PINN
+    problem = FirstOrderODE()
+    model = FeedForward(
+        layers=[4]*2,
+        output_variables=problem.output_variables,
+        input_variables=problem.input_variables,
+        func=Softplus,
+    )
+    pinn = PINN(problem, model, lr=0.03, error_norm='mse', regularizer=0)
+
+    if args.s:
+
+        pinn.span_pts(
+            {'variables': ['x'], 'mode': 'grid', 'n': 1}, locations=['bc'])
+        pinn.span_pts(
+            {'variables': ['x'], 'mode': 'grid', 'n': 30}, locations=['dd'])
+        Plotter().plot_samples(pinn, ['x'])
+        pinn.train(1200, 50)
+        pinn.save_state('pina.ode')
+
+    else:
+        pinn.load_state('pina.ode')
+        plotter = Plotter()
+        plotter.plot(pinn, components=['y'])