Loss Fixing #182 (#184)

* fix doc loss + adding PowerLoss
* adding loss tests folder

---------

Co-authored-by: Dario Coscia <dariocoscia@Dario-Coscia.local>

docs/source/_rst/code.rst

@@ -40,6 +40,15 @@ Layers
 
     ContinuousConv <convolution.rst>
 
+Loss
+------
+
+.. toctree::
+    :maxdepth: 3
+
+    LpLoss <lploss.rst>
+    PowerLoss <powerloss.rst>
+
 Problem
 -------
 

docs/source/_rst/lploss.rst

@@ -0,0 +1,10 @@
+LpLoss
+====
+.. currentmodule:: pina.loss
+
+.. automodule:: pina.loss
+
+.. autoclass:: LpLoss
+   :members:
+   :private-members:
+   :show-inheritance:

docs/source/_rst/pinn.rst

@@ -1,8 +1,8 @@
 PINN
 ====
-.. currentmodule:: pina.pinn
+.. currentmodule:: pina.solvers.pinn
 
-.. automodule:: pina.pinn
+.. automodule:: pina.solvers.pinn
 
 .. autoclass:: PINN
    :members:

docs/source/_rst/powerloss.rst

@@ -0,0 +1,10 @@
+PowerLoss
+=========
+.. currentmodule:: pina.loss
+
+.. automodule:: pina.loss
+
+.. autoclass:: PowerLoss
+   :members:
+   :private-members:
+   :show-inheritance:

pina/loss.py

@@ -1,4 +1,6 @@
-""" Module for EquationInterface class """
+""" Module for Loss class """
+
+
 from abc import ABCMeta, abstractmethod
 from torch.nn.modules.loss import _Loss
 import torch
@@ -55,25 +57,25 @@ class LossInterface(_Loss, metaclass=ABCMeta):
         return ret
 
 class LpLoss(LossInterface):
-    """
+    r"""
     The Lp loss implementation class. Creates a criterion that measures
     the Lp error between each element in the input :math:`x` and
     target :math:`y`.
 
-    The unreduced (i.e. with :attr:`reduction` set to ``'none'``) loss can
+    The unreduced (i.e. with :attr:`reduction` set to ``none``) loss can
     be described as:
 
     .. math::
         \ell(x, y) = L = \{l_1,\dots,l_N\}^\top, \quad
-        l_n = \left| x_n - y_n \right|^p,
+        l_n = \left[\sum_{i=1}^{D} \left| x_n^i - y_n^i \right|^p \right],
     
     If ``'relative'`` is set to true:
 
     .. math::
         \ell(x, y) = L = \{l_1,\dots,l_N\}^\top, \quad
-        l_n = \left[\frac{\left| x_n - y_n \right|^p}{\left|y_n \right|^p}\right]^{1/p},
+        l_n = \frac{ [\sum_{i=1}^{D} | x_n^i - y_n^i|^p] }{[\sum_{i=1}^{D}|y_n^i|^p]},
 
-    where :math:`N` is the batch size. If :attr:`reduction` is not ``'none'``
+    where :math:`N` is the batch size. If :attr:`reduction` is not ``none``
     (default ``'mean'``), then:
 
     .. math::
@@ -88,7 +90,7 @@ class LpLoss(LossInterface):
 
     The sum operation still operates over all the elements, and divides by :math:`n`.
 
-    The division by :math:`n` can be avoided if one sets ``reduction = 'sum'``.
+    The division by :math:`n` can be avoided if one sets :attr:`reduction` to ``sum``.
     """
 
     def __init__(self, p=2, reduction = 'mean', relative = False):
@@ -125,3 +127,77 @@ class LpLoss(LossInterface):
         if self.relative:
             loss = loss / torch.linalg.norm(input, ord=self.p, dim=-1)          
         return self._reduction(loss)
+    
+
+
+class PowerLoss(LossInterface):
+    r"""
+    The PowerLoss loss implementation class. Creates a criterion that measures
+    the error between each element in the input :math:`x` and
+    target :math:`y` powered to a specific integer.
+
+    The unreduced (i.e. with :attr:`reduction` set to ``none``) loss can
+    be described as:
+
+    .. math::
+        \ell(x, y) = L = \{l_1,\dots,l_N\}^\top, \quad
+        l_n = \frac{1}{D}\left[\sum_{i=1}^{D} \left| x_n^i - y_n^i \right|^p \right],
+    
+    If ``'relative'`` is set to true:
+
+    .. math::
+        \ell(x, y) = L = \{l_1,\dots,l_N\}^\top, \quad
+        l_n = \frac{ \sum_{i=1}^{D} | x_n^i - y_n^i|^p }{\sum_{i=1}^{D}|y_n^i|^p},
+
+    where :math:`N` is the batch size. If :attr:`reduction` is not ``none``
+    (default ``'mean'``), then:
+
+    .. math::
+        \ell(x, y) =
+        \begin{cases}
+            \operatorname{mean}(L), & \text{if reduction} = \text{`mean';}\\
+            \operatorname{sum}(L),  & \text{if reduction} = \text{`sum'.}
+        \end{cases}
+
+    :math:`x` and :math:`y` are tensors of arbitrary shapes with a total
+    of :math:`n` elements each.
+
+    The sum operation still operates over all the elements, and divides by :math:`n`.
+
+    The division by :math:`n` can be avoided if one sets :attr:`reduction` to ``sum``.
+    """
+
+    def __init__(self, p=2, reduction = 'mean', relative = False):
+        """
+        :param int p: Degree of Lp norm. It specifies the type of norm to
+            be calculated. See :meth:`torch.linalg.norm` ```'ord'``` to
+            see the possible degrees. Default 2 (euclidean norm).
+        :param str reduction: Specifies the reduction to apply to the output:
+            ``'none'`` | ``'mean'`` | ``'sum'``. ``'none'``: no reduction 
+            will be applied, ``'mean'``: the sum of the output will be divided
+            by the number of elements in the output, ``'sum'``: the output will
+            be summed. Note: :attr:`size_average` and :attr:`reduce` are in the
+            process of being deprecated, and in the meantime, specifying either of
+            those two args will override :attr:`reduction`. Default: ``'mean'``.
+        :param bool relative: Specifies if relative error should be computed.
+        """
+        super().__init__(reduction=reduction)
+
+        # check consistency
+        check_consistency(p, (str,int,float))
+        self.p = p
+        check_consistency(relative, bool)
+        self.relative = relative
+
+    def forward(self, input, target):
+        """Forward method for loss function.
+
+        :param torch.Tensor input: Input tensor from real data.
+        :param torch.Tensor target: Model tensor output.
+        :return: Loss evaluation.
+        :rtype: torch.Tensor
+        """
+        loss = torch.abs((input-target)).pow(self.p).mean(-1)
+        if self.relative:
+            loss = loss / torch.abs(input).pow(self.p).mean(-1)        
+        return self._reduction(loss)

tests/test_loss/test_powerloss.py

@@ -0,0 +1,49 @@
+import torch
+import pytest
+
+from pina.loss import PowerLoss
+
+input = torch.tensor([[3.], [1.], [-8.]])
+target = torch.tensor([[6.], [4.], [2.]])
+available_reductions = ['str', 'mean', 'none']
+
+
+def test_PowerLoss_constructor():
+    # test reduction
+    for reduction in available_reductions:
+        PowerLoss(reduction=reduction)
+    # test p
+    for p in [float('inf'), -float('inf'), 1, 10, -8]:
+        PowerLoss(p=p)
+
+def test_PowerLoss_forward():
+    # l2 loss
+    loss = PowerLoss(p=2, reduction='mean')
+    l2_loss = torch.mean((input-target).pow(2))
+    assert loss(input, target) == l2_loss
+    # l1 loss
+    loss = PowerLoss(p=1, reduction='sum')
+    l1_loss = torch.sum(torch.abs(input-target))
+    assert loss(input, target) == l1_loss
+
+def test_LpRelativeLoss_constructor():
+    # test reduction
+    for reduction in available_reductions:
+        PowerLoss(reduction=reduction, relative=True)
+    # test p
+    for p in [float('inf'), -float('inf'), 1, 10, -8]:
+        PowerLoss(p=p,relative=True)
+
+def test_LpRelativeLoss_forward():
+    # l2 relative loss
+    loss = PowerLoss(p=2, reduction='mean',relative=True)
+    l2_loss = (input-target).pow(2)/input.pow(2)
+    assert loss(input, target) == torch.mean(l2_loss)
+    # l1 relative loss
+    loss = PowerLoss(p=1, reduction='sum',relative=True)
+    l1_loss = torch.abs(input-target)/torch.abs(input)
+    assert loss(input, target) == torch.sum(l1_loss)
+
+
+
+