Add loss functions

Author: pockerman

src/maths/loss_functions.py

@@ -0,0 +1,13 @@
+"""Module loss_functions. Implements basic loss functions
+geared towards using PyTorch
+
+"""
+
+import torch
+
+
+def mse(returns: torch.Tensor, values: torch.Tensor) -> torch.Tensor:
+
+    value_error = returns - values
+    loss = value_error.pow(2).mul(0.5).mean()
+    return loss