Merge pull request #25 from rodgzilla/multiple_choice_head

Simplifying the use of the model to perform different tasks

Author: thomwolf

loss.py

@@ -0,0 +1,69 @@
+import torch
+
+class MultipleChoiceLossCompute:
+    "A Loss compute and train function for multiple choice tasks."
+
+    def __init__(self, lm_criterion, clf_criterion, lm_coef, opt=None):
+        self.lm_criterion = lm_criterion
+        self.clf_criterion = clf_criterion
+        self.lm_coef = lm_coef
+        self.opt = opt
+
+    def __call__(self, X, Y, M, clf_logits, lm_logits=None, only_return_losses=False):
+        # Language modeling loss
+        if lm_logits is not None:
+            x_shifted = X[:, :, 1:, 0].contiguous().view(-1)  # Shape: 252
+            M = M.view(-1, M.size(2))
+            lm_losses = self.lm_criterion(lm_logits, x_shifted)
+            lm_losses = lm_losses.view(X.size(0) * X.size(1), X.size(2) - 1)
+            lm_losses = lm_losses * M[:, 1:]
+            lm_losses = lm_losses.sum(1) / torch.sum(M[:, 1:], 1)
+        # Classification loss
+        clf_losses = self.clf_criterion(clf_logits, Y)
+        if only_return_losses:
+            return (clf_losses, lm_losses) if lm_logits is not None else clf_losses
+
+        if self.lm_coef > 0 and lm_logits is not None:
+            train_loss = clf_losses.sum() + self.lm_coef * lm_losses.sum()
+        else:
+            train_loss = clf_losses.sum()
+        train_loss.backward()
+        if self.opt is not None:
+            self.opt.step()
+            self.opt.zero_grad()
+        return train_loss.item()
+
+class ClassificationLossCompute:
+    "A Loss compute and train function for classification tasks."
+
+    def __init__(self, lm_criterion, clf_criterion, lm_coef, opt=None):
+        self.lm_criterion  = lm_criterion
+        self.clf_criterion = clf_criterion
+        self.lm_coef       = lm_coef
+        self.opt           = opt
+
+    def __call__(self, X, Y, M, clf_logits, lm_logits=None, only_return_losses=False):
+        # Language modeling loss
+        if lm_logits is not None:
+            x_shifted = X[:, 1:, 0].contiguous().view(-1)
+            M         = M.view(-1, M.size(-1))
+            lm_losses = self.lm_criterion(lm_logits, x_shifted)
+            lm_losses = lm_losses.view(X.size(0), X.size(-2) - 1)
+            lm_losses = lm_losses * M[:, 1:]
+            lm_losses = lm_losses.sum(1) / torch.sum(M[:, 1:], 1)
+        # Classification loss
+        clf_losses = self.clf_criterion(clf_logits, Y)
+        if only_return_losses:
+            return (clf_losses, lm_losses) if lm_logits is not None else clf_losses
+
+        if self.lm_coef > 0 and lm_logits is not None:
+            train_loss = clf_losses.sum() + self.lm_coef * lm_losses.sum()
+        else:
+            train_loss = clf_losses.sum()
+        train_loss.backward()
+        if self.opt is not None:
+            self.opt.step()
+            self.opt.zero_grad()
+        return train_loss.item()
+
+# TODO Implement a LossCompute class for similiraty tasks.

model_pytorch.py

@@ -2,6 +2,7 @@
 import json
 import math
 import re
+import collections
 
 import numpy as np
 import torch
@@ -187,22 +188,23 @@ def forward(self, h):
         return lm_logits
 
 
-class ClfHead(nn.Module):
+class MultipleChoiceHead(nn.Module):
     """ Classifier Head for the transformer """
 
     def __init__(self, clf_token, cfg):
-        super(ClfHead, self).__init__()
+        super(MultipleChoiceHead, self).__init__()
         self.n_embd = cfg.n_embd
         self.clf_token = clf_token
         self.dropout = nn.Dropout2d(cfg.clf_pdrop)  # To reproduce the noise_shape parameter of TF implementation
         self.linear = nn.Linear(cfg.n_embd, 1)
-        nn.init.normal_(self.linear.weight, std=0.02)
+
+        nn.init.normal_(self.linear.weight, std = 0.02)
         nn.init.normal_(self.linear.bias, 0)
 
     def forward(self, h, x):
         # Classification logits
         clf_h = h.view(-1, self.n_embd)
-        flat = x[:, :, :, 0].contiguous().view(-1)
+        flat = x[..., 0].contiguous().view(-1)
         clf_h = clf_h[flat == self.clf_token, :]
         clf_h = clf_h.view(-1, x.size(1), self.n_embd, 1)
         # This double transposition is there to replicate the behavior
@@ -212,22 +214,90 @@ def forward(self, h, x):
         clf_h = self.dropout(clf_h.transpose(1, 2)).transpose(1, 2)
         clf_h = clf_h.contiguous().view(-1, self.n_embd)
         clf_logits = self.linear(clf_h)
+
         return clf_logits.view(-1, x.size(1))
 
 
+class ClfHead(nn.Module):
+    """Classification Head for the transformer
+
+    TODO: test this class."""
+    def __init__(self, clf_token, cfg, n_class):
+        super(ClfHead, self).__init__()
+        self.n_embd = cfg.n_embd
+        self.clf_token = clf_token
+        self.dropout = nn.Dropout(cfg.clf_pdrop)
+        self.linear = nn.Linear(cfg.n_embd, n_class)
+
+        nn.init.normal_(self.linear.weight, std = 0.02)
+        nn.init.normal_(self.linear.bias, 0)
+
+    def forward(self, h, x):
+        clf_h = h.view(-1, self.n_embd)
+        flat = x[..., 0].contiguous().view(-1)
+        clf_h = clf_h[flat == self.clf_token, :]
+        clf_h = self.dropout(clf_h)
+        clf_logits = self.linear(clf_h)
+
+        return clf_logits
+
+class SimilarityHead(nn.Module):
+    """ Similarity Head for the transformer
+
+        TODO: test this class."""
+    def __init__(self, clf_token, cfg):
+        super(SimilarityHead, self).__init__()
+        self.n_embd = cfg.n_embd
+        self.clf_token = clf_token
+        self.dropout = nn.Dropout(cfg.clf_pdrop)
+        self.linear = nn.Linear(cfg.n_embd, 1)
+
+        nn.init.normal_(self.linear.weight, std = 0.02)
+        nn.init.normal_(self.linear.bias, 0)
+
+    def forward(self, h, x):
+        sim_h = h.view(-1, self.n_embd)
+        flat = x[..., 0].contiguous().view(-1)
+        sim_h = sim_h[flat == self.clf_token, :]
+        sim_h = self.dropout(sim_h)
+        sim_h = sim_h.sum(dim = 1)
+        sim_logits = self.linear(sim_h)
+
+        return sim_logits
+
 class DoubleHeadModel(nn.Module):
-    """ Transformer with language model and classification heads """
-    def __init__(self, cfg, clf_token, vocab=40990, n_ctx=512):
+    """ Transformer with language model and task specific heads """
+    def __init__(self, cfg, clf_token, task_head_type, vocab=40990, n_ctx=512):
         super(DoubleHeadModel, self).__init__()
         self.transformer = TransformerModel(cfg, vocab=vocab, n_ctx=n_ctx)
         self.lm_head = LMHead(self.transformer, cfg)
-        self.clf_head = ClfHead(clf_token, cfg)
+        if isinstance(task_head_type, str):
+            if task_head_type == 'multiple_choice':
+                self.task_head = MultipleChoiceHead(clf_token, cfg)
+            elif task_head_type == 'similarity':
+                self.task_head = SimilarityHead(clf_token, cfg)
+            elif task_head_type == 'inference':
+                # the three classes correspond to entailment, contradiction and neutral.
+                self.task_head = ClfHead(clf_token, cfg, 3)
+            else:
+                raise ValueError("task_head_type is expected to be 'multiple_choice' "
+                                 "'similarity', 'inference' or ('classification', n_class) "
+                                 f"got {task_head_type}.")
+        elif isinstance(task_head_type, collections.abc.Sequence) and len(task_head_type) == 2 and \
+             task_head_type[0] == 'classification':
+            n_class = task_head_type[1]
+            self.task_head = ClfHead(clf_token, cfg, n_class)
+        else:
+            raise ValueError("task_head_type is expected to be 'multiple_choice' "
+                             "'similarity', 'inference' or ('classification', n_class) "
+                             f"got {task_head_type}.")
 
     def forward(self, x):
         h = self.transformer(x)
         lm_logits = self.lm_head(h)
-        clf_logits = self.clf_head(h, x)
-        return lm_logits, clf_logits
+        task_logits = self.task_head(h, x)
+
+        return lm_logits, task_logits
 
 
 def load_openai_pretrained_model(model, n_ctx=-1, n_special=-1, n_transfer=12, n_embd=768, path='./model/',

train.py

@@ -15,41 +15,7 @@
 from text_utils import TextEncoder
 from utils import (encode_dataset, iter_data,
                    ResultLogger, make_path)
-
-
-class LossCompute:
-    "A Loss compute and train function."
-
-    def __init__(self, lm_criterion, clf_criterion, lm_coef, opt=None):
-        self.lm_criterion = lm_criterion
-        self.clf_criterion = clf_criterion
-        self.lm_coef = lm_coef
-        self.opt = opt
-
-    def __call__(self, X, Y, M, clf_logits, lm_logits=None, only_return_losses=False):
-        # Language modeling loss
-        if lm_logits is not None:
-            x_shifted = X[:, :, 1:, 0].contiguous().view(-1)  # Shape: 252
-            M = M.view(-1, M.size(2))
-            lm_losses = self.lm_criterion(lm_logits, x_shifted)
-            lm_losses = lm_losses.view(X.size(0) * X.size(1), X.size(2) - 1)
-            lm_losses = lm_losses * M[:, 1:]
-            lm_losses = lm_losses.sum(1) / torch.sum(M[:, 1:], 1)
-        # Classification loss
-        clf_losses = self.clf_criterion(clf_logits, Y)
-        if only_return_losses:
-            return (clf_losses, lm_losses) if lm_logits is not None else clf_losses
-
-        if self.lm_coef > 0 and lm_logits is not None:
-            train_loss = clf_losses.sum() + self.lm_coef * lm_losses.sum()
-        else:
-            train_loss = clf_losses.sum()
-        train_loss.backward()
-        if self.opt is not None:
-            self.opt.step()
-            self.opt.zero_grad()
-        return train_loss.item()
-
+from loss import MultipleChoiceLossCompute
 
 def transform_roc(X1, X2, X3):
     n_batch = len(X1)
@@ -263,7 +229,7 @@ def run_epoch():
     n_batch_train = args.n_batch * max(n_gpu, 1)
     n_updates_total = (n_train // n_batch_train) * args.n_iter
 
-    dh_model = DoubleHeadModel(args, clf_token, vocab, n_ctx)
+    dh_model = DoubleHeadModel(args, clf_token, 'multiple_choice', vocab, n_ctx)
 
     criterion = nn.CrossEntropyLoss(reduce=False)
     model_opt = OpenAIAdam(dh_model.parameters(),
@@ -277,10 +243,10 @@ def run_epoch():
                            l2=args.l2,
                            vector_l2=args.vector_l2,
                            max_grad_norm=args.max_grad_norm)
-    compute_loss_fct = LossCompute(criterion,
-                                   criterion,
-                                   args.lm_coef,
-                                   model_opt)
+    compute_loss_fct = MultipleChoiceLossCompute(criterion,
+                                                 criterion,
+                                                 args.lm_coef,
+                                                 model_opt)
     load_openai_pretrained_model(dh_model.transformer, n_ctx=n_ctx, n_special=n_special)
 
     dh_model.to(device)