From 46391257ff50848efa1aa251ab3f15dc8b7a2d2c Mon Sep 17 00:00:00 2001
From: Jordan Gong <jordan.gong@protonmail.com>
Date: Sat, 27 Feb 2021 22:14:21 +0800
Subject: Implement Batch Hard triplet loss and soft margin

---
 utils/triplet_loss.py | 84 ++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 56 insertions(+), 28 deletions(-)

(limited to 'utils/triplet_loss.py')

diff --git a/utils/triplet_loss.py b/utils/triplet_loss.py
index 0df2188..c3e5802 100644
--- a/utils/triplet_loss.py
+++ b/utils/triplet_loss.py
@@ -1,32 +1,36 @@
+from typing import Optional
+
 import torch
 import torch.nn as nn
 import torch.nn.functional as F
 
 
-class BatchAllTripletLoss(nn.Module):
-    def __init__(self, margin: float = 0.2):
+class BatchTripletLoss(nn.Module):
+    def __init__(
+            self,
+            is_hard: bool = True,
+            margin: Optional[float] = 0.2,
+    ):
         super().__init__()
+        self.is_hard = is_hard
         self.margin = margin
 
     def forward(self, x, y):
         p, n, c = x.size()
-
         dist = self._batch_distance(x)
-        positive_negative_dist = self._hard_distance(dist, y, p, n)
-        all_loss = F.relu(self.margin + positive_negative_dist).view(p, -1)
-        parted_loss_mean = self._none_zero_parted_mean(all_loss)
 
-        return parted_loss_mean
+        if self.is_hard:
+            positive_negative_dist = self._hard_distance(dist, y, p, n)
+        else:  # is_all
+            positive_negative_dist = self._all_distance(dist, y, p, n)
 
-    @staticmethod
-    def _hard_distance(dist, y, p, n):
-        hard_positive_mask = y.unsqueeze(1) == y.unsqueeze(2)
-        hard_negative_mask = y.unsqueeze(1) != y.unsqueeze(2)
-        all_hard_positive = dist[hard_positive_mask].view(p, n, -1, 1)
-        all_hard_negative = dist[hard_negative_mask].view(p, n, 1, -1)
-        positive_negative_dist = all_hard_positive - all_hard_negative
+        if self.margin:
+            all_loss = F.relu(self.margin + positive_negative_dist).view(p, -1)
+        else:
+            all_loss = F.softplus(positive_negative_dist).view(p, -1)
+        non_zero_mean, non_zero_counts = self._none_zero_parted_mean(all_loss)
 
-        return positive_negative_dist
+        return non_zero_mean, dist.mean((1, 2)), non_zero_counts
 
     @staticmethod
     def _batch_distance(x):
@@ -38,41 +42,65 @@ class BatchAllTripletLoss(nn.Module):
         dist = torch.sqrt(
             F.relu(x1_squared_sum - 2 * x1_times_x2_sum + x2_squared_sum)
         )
-
         return dist
 
+    @staticmethod
+    def _hard_distance(dist, y, p, n):
+        positive_mask = y.unsqueeze(1) == y.unsqueeze(2)
+        negative_mask = y.unsqueeze(1) != y.unsqueeze(2)
+        hard_positive = dist[positive_mask].view(p, n, -1).max(-1).values
+        hard_negative = dist[negative_mask].view(p, n, -1).min(-1).values
+        positive_negative_dist = hard_positive - hard_negative
+
+        return positive_negative_dist
+
+    @staticmethod
+    def _all_distance(dist, y, p, n):
+        positive_mask = y.unsqueeze(1) == y.unsqueeze(2)
+        negative_mask = y.unsqueeze(1) != y.unsqueeze(2)
+        all_positive = dist[positive_mask].view(p, n, -1, 1)
+        all_negative = dist[negative_mask].view(p, n, 1, -1)
+        positive_negative_dist = all_positive - all_negative
+
+        return positive_negative_dist
+
     @staticmethod
     def _none_zero_parted_mean(all_loss):
         # Non-zero parted mean
-        non_zero_counts = (all_loss != 0).sum(1)
-        parted_loss_mean = all_loss.sum(1) / non_zero_counts
-        parted_loss_mean[non_zero_counts == 0] = 0
+        non_zero_counts = (all_loss != 0).sum(1).float()
+        non_zero_mean = all_loss.sum(1) / non_zero_counts
+        non_zero_mean[non_zero_counts == 0] = 0
 
-        return parted_loss_mean
+        return non_zero_mean, non_zero_counts
 
 
-class JointBatchAllTripletLoss(BatchAllTripletLoss):
+class JointBatchTripletLoss(BatchTripletLoss):
     def __init__(
             self,
             hpm_num_parts: int,
+            is_hard: bool = True,
             margins: tuple[float, float] = (0.2, 0.2)
     ):
-        super().__init__()
+        super().__init__(is_hard)
         self.hpm_num_parts = hpm_num_parts
         self.margin_hpm, self.margin_pn = margins
 
     def forward(self, x, y):
         p, n, c = x.size()
-
         dist = self._batch_distance(x)
-        positive_negative_dist = self._hard_distance(dist, y, p, n)
+
+        if self.is_hard:
+            positive_negative_dist = self._hard_distance(dist, y, p, n)
+        else:  # is_all
+            positive_negative_dist = self._all_distance(dist, y, p, n)
+
         hpm_part_loss = F.relu(
             self.margin_hpm + positive_negative_dist[:self.hpm_num_parts]
-        ).view(self.hpm_num_parts, -1)
+        )
         pn_part_loss = F.relu(
             self.margin_pn + positive_negative_dist[self.hpm_num_parts:]
-        ).view(p - self.hpm_num_parts, -1)
+        )
         all_loss = torch.cat((hpm_part_loss, pn_part_loss)).view(p, -1)
-        parted_loss_mean = self._none_zero_parted_mean(all_loss)
+        non_zero_mean, non_zero_counts = self._none_zero_parted_mean(all_loss)
 
-        return parted_loss_mean
+        return non_zero_mean, dist.mean((1, 2)), non_zero_counts
-- 
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