From 8237f2c5d01b5c490915e26427913c317560d035 Mon Sep 17 00:00:00 2001
From: Francisco Rivera Valverde
 <44504424+franchuterivera@users.noreply.github.com>
Date: Thu, 24 Jun 2021 12:28:15 +0200
Subject: [PATCH] Fix_248 (#263)

---
 autoPyTorch/utils/implementations.py | 12 ++---
 test/test_pipeline/test_losses.py    | 75 +++++++++++++++++++++++++++-
 2 files changed, 79 insertions(+), 8 deletions(-)

diff --git a/autoPyTorch/utils/implementations.py b/autoPyTorch/utils/implementations.py
index 2130cfd6b..a0b020622 100644
--- a/autoPyTorch/utils/implementations.py
+++ b/autoPyTorch/utils/implementations.py
@@ -25,17 +25,17 @@ class LossWeightStrategyWeighted():
     def __call__(self, y: Union[np.ndarray, torch.Tensor]) -> np.ndarray:
         if isinstance(y, torch.Tensor):
             y = y.detach().cpu().numpy() if y.is_cuda else y.numpy()
-        if isinstance(y[0], str):
-            y = y.astype('float64')
         counts = np.sum(y, axis=0)
         total_weight = y.shape[0]
 
-        if len(y.shape) > 1:
+        if len(y.shape) > 1 and y.shape[1] != 1:
+            # In this case, the second axis represents classes
             weight_per_class = total_weight / y.shape[1]
             weights = (np.ones(y.shape[1]) * weight_per_class) / np.maximum(counts, 1)
         else:
+            # Numpy unique return the sorted classes. This is desirable as
+            # weights recieved by PyTorch is a sorted list of classes
             classes, counts = np.unique(y, axis=0, return_counts=True)
-            classes, counts = classes[::-1], counts[::-1]
             weight_per_class = total_weight / classes.shape[0]
             weights = (np.ones(classes.shape[0]) * weight_per_class) / counts
 
@@ -50,10 +50,8 @@ class LossWeightStrategyWeightedBinary():
     def __call__(self, y: Union[np.ndarray, torch.Tensor]) -> np.ndarray:
         if isinstance(y, torch.Tensor):
             y = y.detach().cpu().numpy() if y.is_cuda else y.numpy()
-        if isinstance(y[0], str):
-            y = y.astype('float64')
         counts_one = np.sum(y, axis=0)
-        counts_zero = counts_one + (-y.shape[0])
+        counts_zero = y.shape[0] - counts_one
         weights = counts_zero / np.maximum(counts_one, 1)
 
         return np.array(weights)
diff --git a/test/test_pipeline/test_losses.py b/test/test_pipeline/test_losses.py
index 9f23f3e9f..3eeba6a70 100644
--- a/test/test_pipeline/test_losses.py
+++ b/test/test_pipeline/test_losses.py
@@ -1,3 +1,5 @@
+import numpy as np
+
 import pytest
 
 import torch
@@ -5,7 +7,11 @@
 from torch.nn.modules.loss import _Loss as Loss
 
 from autoPyTorch.pipeline.components.training.losses import get_loss, losses
-from autoPyTorch.utils.implementations import get_loss_weight_strategy
+from autoPyTorch.utils.implementations import (
+    LossWeightStrategyWeighted,
+    LossWeightStrategyWeightedBinary,
+    get_loss_weight_strategy,
+)
 
 
 @pytest.mark.parametrize('output_type', ['multiclass',
@@ -66,3 +72,70 @@ def test_loss_dict():
             assert isinstance(loss['module'](), Loss)
             assert 'supported_output_types' in loss.keys()
             assert isinstance(loss['supported_output_types'], list)
+
+
+@pytest.mark.parametrize('target,expected_weights', [
+    (
+        # Expected 4 classes where first one is majority one
+        np.array([[1, 0, 0, 0], [1, 0, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]),
+        # We reduce the contribution of the first class which has double elements
+        np.array([0.5, 1., 1., 1.]),
+    ),
+    (
+        # Expected 2 classes -- multilable format
+        np.array([[1, 0], [1, 0], [1, 0], [0, 1]]),
+        # We reduce the contribution of the first class which 3 to 1 ratio
+        np.array([2 / 3, 2]),
+    ),
+    (
+        # Expected 2 classes -- (-1, 1) format
+        np.array([[1], [1], [1], [0]]),
+        # We reduce the contribution of the second class, which has a 3 to 1 ratio
+        np.array([2, 2 / 3]),
+    ),
+    (
+        # Expected 2 classes -- single column
+        # We have to reduce the contribution of the second class with 5 to 1 ratio
+        np.array([1, 1, 1, 1, 1, 0]),
+        # We reduce the contribution of the first class which has double elements
+        np.array([3, 6 / 10]),
+    ),
+])
+def test_lossweightstrategyweighted(target, expected_weights):
+    weights = LossWeightStrategyWeighted()(target)
+    np.testing.assert_array_equal(weights, expected_weights)
+    assert nn.CrossEntropyLoss(weight=torch.Tensor(weights))(
+        torch.zeros(target.shape[0], len(weights)).float(),
+        torch.from_numpy(target.argmax(1)).long() if len(target.shape) > 1
+        else torch.from_numpy(target).long()
+    ) > 0
+
+
+@pytest.mark.parametrize('target,expected_weights', [
+    (
+        # Expected 2 classes -- multilable format
+        np.array([[1, 0], [1, 0], [1, 0], [0, 1]]),
+        # We reduce the contribution of the first class which 3 to 1 ratio
+        np.array([1 / 3, 3]),
+    ),
+    (
+        # Expected 2 classes -- (-1, 1) format
+        np.array([[1], [1], [1], [0]]),
+        # We reduce the contribution of the second class, which has a 3 to 1 ratio
+        np.array([1 / 3]),
+    ),
+    (
+        # Expected 2 classes -- single column
+        # We have to reduce the contribution of the second class with 5 to 1 ratio
+        np.array([1, 1, 1, 1, 1, 0]),
+        # We reduce the contribution of the first class which has double elements
+        np.array([0.2]),
+    ),
+])
+def test_lossweightstrategyweightedbinary(target, expected_weights):
+    weights = LossWeightStrategyWeightedBinary()(target)
+    np.testing.assert_array_equal(weights, expected_weights)
+    assert nn.BCEWithLogitsLoss(pos_weight=torch.Tensor(weights))(
+        torch.from_numpy(target).float(),
+        torch.from_numpy(target).float(),
+    ) > 0