[Model] Support Multi-GPU for Transformer model (#356)

* multi-process version of transformer

* lots of fix

* fix bugs and accum gradients for multiple batches

* many fixes

* minor

* upd

* set torch device

* fix bugs

* fix and minor

* comments and clean up

* uncomment viz code

examples/pytorch/transformer/dataset/__init__.py

@@ -2,14 +2,14 @@ from .graph import *
 from .fields import *
 from .utils import prepare_dataset
 import os
-import numpy as np
+import random
 
-class ClassificationDataset:
+class ClassificationDataset(object):
     "Dataset class for classification task."
     def __init__(self):
         raise NotImplementedError
 
-class TranslationDataset:
+class TranslationDataset(object):
     '''
     Dataset class for translation task.
     By default, the source language shares the same vocabulary with the target language.
@@ -22,17 +22,17 @@ class TranslationDataset:
         vocab_path = os.path.join(path, vocab)
         self.src = {}
         self.tgt = {}
-        with open(os.path.join(path, train + '.' + exts[0]), 'r') as f:
+        with open(os.path.join(path, train + '.' + exts[0]), 'r', encoding='utf-8') as f:
             self.src['train'] = f.readlines()
-        with open(os.path.join(path, train + '.' + exts[1]), 'r') as f:
+        with open(os.path.join(path, train + '.' + exts[1]), 'r', encoding='utf-8') as f:
             self.tgt['train'] = f.readlines()
-        with open(os.path.join(path, valid + '.' + exts[0]), 'r') as f:
+        with open(os.path.join(path, valid + '.' + exts[0]), 'r', encoding='utf-8') as f:
             self.src['valid'] = f.readlines()
-        with open(os.path.join(path, valid + '.' + exts[1]), 'r') as f:
+        with open(os.path.join(path, valid + '.' + exts[1]), 'r', encoding='utf-8') as f:
             self.tgt['valid'] = f.readlines()
-        with open(os.path.join(path, test + '.' + exts[0]), 'r') as f:
+        with open(os.path.join(path, test + '.' + exts[0]), 'r', encoding='utf-8') as f:
             self.src['test'] = f.readlines()
-        with open(os.path.join(path, test + '.' + exts[1]), 'r') as f:
+        with open(os.path.join(path, test + '.' + exts[1]), 'r', encoding='utf-8') as f:
             self.tgt['test'] = f.readlines()
 
         if not os.path.exists(vocab_path):
@@ -90,20 +90,30 @@ class TranslationDataset:
     def eos_id(self):
         return self.vocab[self.EOS_TOKEN]
 
-    def __call__(self, graph_pool, mode='train', batch_size=32, k=1, devices=['cpu']):
+    def __call__(self, graph_pool, mode='train', batch_size=32, k=1,
+                 device='cpu', dev_rank=0, ndev=1):
         '''
         Create a batched graph correspond to the mini-batch of the dataset.
         args:
             graph_pool: a GraphPool object for accelerating.
             mode: train/valid/test
             batch_size: batch size
-            devices: ['cpu'] or a list of gpu ids.
-            k: beam size(only required for test) 
+            k: beam size(only required for test)
+            device: str or torch.device
+            dev_rank: rank (id) of current device
+            ndev: number of devices
         '''
-        dev_id, gs = 0, []
         src_data, tgt_data = self.src[mode], self.tgt[mode]
         n = len(src_data)
-        order = np.random.permutation(n) if mode == 'train' else range(n)
+        # make sure all devices have the same number of batch
+        n = n // ndev * ndev
+
+        # XXX: partition then shuffle may not be equivalent to shuffle then
+        # partition
+        order = list(range(dev_rank, n, ndev))
+        if mode == 'train':
+            random.shuffle(order)
+
         src_buf, tgt_buf = [], []
 
         for idx in order:
@@ -115,22 +125,16 @@ class TranslationDataset:
             tgt_buf.append(tgt_sample)
             if len(src_buf) == batch_size:
                 if mode == 'test':
-                    assert len(devices) == 1 # we only allow single gpu for inference
-                    yield graph_pool.beam(src_buf, self.sos_id, self.MAX_LENGTH, k, device=devices[0])
+                    yield graph_pool.beam(src_buf, self.sos_id, self.MAX_LENGTH, k, device=device)
                 else:
-                    gs.append(graph_pool(src_buf, tgt_buf, device=devices[dev_id]))
-                    dev_id += 1
-                    if dev_id == len(devices):
-                        yield gs if len(devices) > 1 else gs[0]
-                        dev_id, gs = 0, []
+                    yield graph_pool(src_buf, tgt_buf, device=device)
                 src_buf, tgt_buf = [], []
 
         if len(src_buf) != 0:
             if mode == 'test':
-                yield graph_pool.beam(src_buf, self.sos_id, self.MAX_LENGTH, k, device=devices[0])
+                yield graph_pool.beam(src_buf, self.sos_id, self.MAX_LENGTH, k, device=device)
             else:
-                gs.append(graph_pool(src_buf, tgt_buf, device=devices[dev_id]))
-                yield gs if len(devices) > 1 else gs[0]
+                yield graph_pool(src_buf, tgt_buf, device=device)
 
     def get_sequence(self, batch):
         "return a list of sequence from a list of index arrays"
@@ -151,8 +155,8 @@ def get_dataset(dataset):
         raise NotImplementedError
     elif dataset == 'copy' or dataset == 'sort':
         return TranslationDataset(
-            'data/{}'.format(dataset), 
-            ('in', 'out'), 
+            'data/{}'.format(dataset),
+            ('in', 'out'),
             train='train',
             valid='valid',
             test='test',

examples/pytorch/transformer/dataset/fields.py

@@ -16,7 +16,7 @@ class Vocab:
             self.vocab_lst.append(self.pad_token)
         if self.unk_token is not None:
             self.vocab_lst.append(self.unk_token)
-        with open(path, 'r') as f:
+        with open(path, 'r', encoding='utf-8') as f:
             for token in f.readlines():
                 token = token.strip()
                 self.vocab_lst.append(token)

examples/pytorch/transformer/loss/__init__.py

 import torch as T
 import torch.nn as nn
 import torch.nn.functional as F
+import torch.distributed as dist
 
 class LabelSmoothing(nn.Module):
     """
@@ -37,14 +38,37 @@ class LabelSmoothing(nn.Module):
 
 class SimpleLossCompute(nn.Module):
     eps=1e-8
-    def __init__(self, criterion, opt=None):
-        """
-        opt is required during training
+    def __init__(self, criterion, grad_accum, opt=None):
+        """Loss function and optimizer for single device
+
+        Parameters
+        ----------
+        criterion: torch.nn.Module
+            criterion to compute loss
+        grad_accum: int
+            number of batches to accumulate gradients
+        opt: Optimizer
+            Model optimizer to use. If None, then no backward and update will be
+            performed
         """
         super(SimpleLossCompute, self).__init__()
         self.criterion = criterion
         self.opt = opt
-        self.reset()
+        self.acc_loss = 0
+        self.n_correct = 0
+        self.norm_term = 0
+        self.loss = 0
+        self.batch_count = 0
+        self.grad_accum = grad_accum
+
+    def __enter__(self):
+        self.batch_count = 0
+
+    def __exit__(self, type, value, traceback):
+        # if not enough batches accumulated and there are gradients not applied,
+        # do one more step
+        if self.batch_count > 0:
+            self.step()
 
     @property
     def avg_loss(self):
@@ -54,32 +78,56 @@ class SimpleLossCompute(nn.Module):
     def accuracy(self):
         return (self.n_correct + self.eps) / (self.norm_term + self.eps)
 
-    def reset(self):
-        self.acc_loss = 0
-        self.n_correct = 0
-        self.norm_term = 0
+    def step(self):
+        self.opt.step()
+        self.opt.optimizer.zero_grad()
+
+    def backward_and_step(self):
+        self.loss.backward()
+        self.batch_count += 1
+        # accumulate self.grad_accum times then synchronize and update
+        if self.batch_count == self.grad_accum:
+            self.step()
+            self.batch_count = 0
 
     def __call__(self, y_pred, y, norm):
         y_pred = y_pred.contiguous().view(-1, y_pred.shape[-1])
         y = y.contiguous().view(-1)
-        loss = self.criterion(
-            y_pred, y
-        ) / norm
+        self.loss = self.criterion(y_pred, y) / norm
         if self.opt is not None:
-            loss.backward()
-            self.opt.step()
-            self.opt.optimizer.zero_grad()
+            self.backward_and_step()
         self.n_correct += ((y_pred.max(dim=-1)[1] == y) & (y != self.criterion.padding_idx)).sum().item()
-        self.acc_loss += loss.item() * norm
+        self.acc_loss += self.loss.item() * norm
         self.norm_term += norm
-        return loss.item() * norm
+        return self.loss.item() * norm
 
 class MultiGPULossCompute(SimpleLossCompute):
-    def __init__(self, criterion, devices, opt=None, chunk_size=5):
-        self.criterion = criterion
-        self.opt = opt
-        self.devices = devices
-        self.chunk_size = chunk_size
+    def __init__(self, criterion, ndev, grad_accum, model, opt=None):
+        """Loss function and optimizer for multiple devices
+
+        Parameters
+        ----------
+        criterion: torch.nn.Module
+            criterion to compute loss
+        ndev: int
+            number of devices used
+        grad_accum: int
+            number of batches to accumulate gradients
+        model: torch.nn.Module
+            model to optimizer (needed to iterate and synchronize all parameters)
+        opt: Optimizer
+            Model optimizer to use. If None, then no backward and update will be
+            performed
+        """
+        super(MultiGPULossCompute, self).__init__(criterion, grad_accum, opt=opt)
+        self.ndev = ndev
+        self.model = model
 
-    def __call__(self, y_preds, ys, norms):
-        pass
+    def step(self):
+        # multi-gpu synchronize gradients
+        for param in self.model.parameters():
+            if param.requires_grad and param.grad is not None:
+                dist.all_reduce(param.grad.data, op=dist.ReduceOp.SUM)
+                param.grad.data /= self.ndev
+        self.opt.step()
+        self.opt.optimizer.zero_grad()

examples/pytorch/transformer/modules/attention.py

@@ -12,7 +12,7 @@ class MultiHeadAttention(nn.Module):
         self.h = h
         # W_q, W_k, W_v, W_o
         self.linears = clones(
-            nn.Linear(dim_model, dim_model), 4
+            nn.Linear(dim_model, dim_model, bias=False), 4
         )
 
     def get(self, x, fields='qkv'):

examples/pytorch/transformer/modules/models.py

@@ -46,11 +46,11 @@ class Decoder(nn.Module):
         layer = self.layers[i]
         def func(nodes):
             x = nodes.data['x']
-            if fields == 'kv':
-                norm_x = x # In enc-dec attention, x has already been normalized.
+            norm_x = layer.sublayer[l].norm(x) if fields.startswith('q') else x
+            if fields != 'qkv':
+                return layer.src_attn.get(norm_x, fields)
             else:
-                norm_x = layer.sublayer[l].norm(x)
-            return layer.self_attn.get(norm_x, fields)
+                return layer.self_attn.get(norm_x, fields)
         return func
 
     def post_func(self, i, l=0):
@@ -64,8 +64,6 @@ class Decoder(nn.Module):
             return {'x': x if i < self.N - 1 else self.norm(x)}
         return func
 
-lock = threading.Lock()
-
 class Transformer(nn.Module):
     def __init__(self, encoder, decoder, src_embed, tgt_embed, pos_enc, generator, h, d_k):
         super(Transformer, self).__init__()
@@ -124,9 +122,10 @@ class Transformer(nn.Module):
             self.update_graph(g, edges, [(pre_q, nodes), (pre_kv, nodes_e)], [(post_func, nodes)])
 
         # visualize attention
-        with lock:
+        """
             if self.att_weight_map is None:
                 self._register_att_map(g, graph.nid_arr['enc'][VIZ_IDX], graph.nid_arr['dec'][VIZ_IDX])
+        """
 
         return self.generator(g.ndata['x'][nids['dec']])
 

examples/pytorch/transformer/parallel.py

-# Mostly then same with PyTorch 
-import threading
-import torch
-
-def get_a_var(obj):
-    if isinstance(obj, torch.Tensor):
-        return obj
-
-    if isinstance(obj, list) or isinstance(obj, tuple):
-        for result in map(get_a_var, obj):
-            if isinstance(result, torch.Tensor):
-                return result
-    if isinstance(obj, dict):
-        for result in map(get_a_var, obj.items()):
-            if isinstance(result, torch.Tensor):
-                return result
-    return None
-
-
-def parallel_apply(modules, inputs):
-    assert len(modules) == len(inputs)
-    lock = threading.Lock()
-    results = {}
-    grad_enabled = torch.is_grad_enabled()
-
-    def _worker(i, module, input):
-        torch.set_grad_enabled(grad_enabled)
-        try:
-            #with torch.cuda.device(device):
-            output = module(input)
-            with lock:
-                results[i] = output
-        except Exception as e:
-            with lock:
-                results[i] = e
-
-    if len(modules) > 1:
-        threads = [threading.Thread(target=_worker,
-                                    args=(i, module, input))
-                   for i, (module, input) in
-                   enumerate(zip(modules, inputs))]
-
-        for thread in threads:
-            thread.start()
-        for thread in threads:
-            thread.join()
-    else:
-        _worker(0, modules[0], inputs[0])
-
-    outputs = []
-    for i in range(len(inputs)):
-        output = results[i]
-        if isinstance(output, Exception):
-            raise output
-        outputs.append(output)
-    return outputs

examples/pytorch/transformer/translation_train.py

-"""
-In current version we use multi30k as the default training and validation set.
-Multi-GPU support is required to train the model on WMT14.
-"""
 from modules import *
-from parallel import *
-from loss import * 
+from loss import *
 from optims import *
 from dataset import *
 from modules.config import *
-from modules.viz import *
-from tqdm import tqdm
+#from modules.viz import *
 import numpy as np
 import argparse
+import torch
+from functools import partial
+import torch.distributed as dist
 
-def run_epoch(data_iter, model, loss_compute, is_train=True):
+def run_epoch(epoch, data_iter, dev_rank, ndev, model, loss_compute, is_train=True):
     universal = isinstance(model, UTransformer)
-    for i, g in tqdm(enumerate(data_iter)):
-        with T.set_grad_enabled(is_train):
-            if isinstance(model, list):
-                model = model[:len(gs)]
-                output = parallel_apply(model, g)
-                tgt_y = [g.tgt_y for g in gs]
-                n_tokens = [g.n_tokens for g in gs]
-            else:
+    with loss_compute:
+        for i, g in enumerate(data_iter):
+            with T.set_grad_enabled(is_train):
                 if universal:
                     output, loss_act = model(g)
                     if is_train: loss_act.backward(retain_graph=True)
@@ -30,70 +22,134 @@ def run_epoch(data_iter, model, loss_compute, is_train=True):
                     output = model(g)
                 tgt_y = g.tgt_y
                 n_tokens = g.n_tokens
-            loss = loss_compute(output, tgt_y, n_tokens)
+                loss = loss_compute(output, tgt_y, n_tokens)
 
     if universal:
         for step in range(1, model.MAX_DEPTH + 1):
             print("nodes entering step {}: {:.2f}%".format(step, (1.0 * model.stat[step] / model.stat[0])))
         model.reset_stat()
-    print('average loss: {}'.format(loss_compute.avg_loss))
-    print('accuracy: {}'.format(loss_compute.accuracy))
+    print('Epoch {} {}: Dev {} average loss: {}, accuracy {}'.format(
+        epoch, "Training" if is_train else "Evaluating",
+        dev_rank, loss_compute.avg_loss, loss_compute.accuracy))
 
-if __name__ == '__main__':
-    if not os.path.exists('checkpoints'):
-        os.makedirs('checkpoints')
-    np.random.seed(1111)
-    argparser = argparse.ArgumentParser('training translation model')
-    argparser.add_argument('--gpus', default='-1', type=str, help='gpu id')
-    argparser.add_argument('--N', default=6, type=int, help='enc/dec layers')
-    argparser.add_argument('--dataset', default='multi30k', help='dataset')
-    argparser.add_argument('--batch', default=128, type=int, help='batch size')
-    argparser.add_argument('--viz', action='store_true', help='visualize attention')
-    argparser.add_argument('--universal', action='store_true', help='use universal transformer')
-    args = argparser.parse_args()
-    args_filter = ['batch', 'gpus', 'viz']
-    exp_setting = '-'.join('{}'.format(v) for k, v in vars(args).items() if k not in args_filter)
-    devices = ['cpu'] if args.gpus == '-1' else [int(gpu_id) for gpu_id in args.gpus.split(',')]
+def run(dev_id, args):
+    dist_init_method = 'tcp://{master_ip}:{master_port}'.format(
+        master_ip=args.master_ip, master_port=args.master_port)
+    world_size = args.ngpu
+    torch.distributed.init_process_group(backend="nccl",
+                                         init_method=dist_init_method,
+                                         world_size=world_size,
+                                         rank=dev_id)
+    gpu_rank = torch.distributed.get_rank()
+    assert gpu_rank == dev_id
+    main(dev_id, args)
 
+def main(dev_id, args):
+    if dev_id == -1:
+        device = torch.device('cpu')
+    else:
+        device = torch.device('cuda:{}'.format(dev_id))
+    # Set current device
+    th.cuda.set_device(device)
+    # Prepare dataset
     dataset = get_dataset(args.dataset)
-
     V = dataset.vocab_size
     criterion = LabelSmoothing(V, padding_idx=dataset.pad_id, smoothing=0.1)
     dim_model = 512
-
+    # Build graph pool
     graph_pool = GraphPool()
-    model = make_model(V, V, N=args.N, dim_model=dim_model, universal=args.universal)
-
+    # Create model
+    model = make_model(V, V, N=args.N, dim_model=dim_model,
+                       universal=args.universal)
     # Sharing weights between Encoder & Decoder
     model.src_embed.lut.weight = model.tgt_embed.lut.weight
     model.generator.proj.weight = model.tgt_embed.lut.weight
+    # Move model to corresponding device
+    model, criterion = model.to(device), criterion.to(device)
+    # Loss function
+    if args.ngpu > 1:
+        dev_rank = dev_id # current device id
+        ndev = args.ngpu # number of devices (including cpu)
+        loss_compute = partial(MultiGPULossCompute, criterion, args.ngpu,
+                               args.grad_accum, model)
+    else: # cpu or single gpu case
+        dev_rank = 0
+        ndev = 1
+        loss_compute = partial(SimpleLossCompute, criterion, args.grad_accum)
 
-    model, criterion = model.to(devices[0]), criterion.to(devices[0])
-    model_opt = NoamOpt(dim_model, 1, 400,
-                        T.optim.Adam(model.parameters(), lr=1e-3, betas=(0.9, 0.98), eps=1e-9))
-    if len(devices) > 1:
-        model, criterion = map(nn.parallel.replicate, [model, criterion], [devices, devices])
-    loss_compute = SimpleLossCompute if len(devices) == 1 else MultiGPULossCompute
+    if ndev > 1:
+        for param in model.parameters():
+            dist.all_reduce(param.data, op=dist.ReduceOp.SUM)
+            param.data /= ndev
 
+    # Optimizer
+    model_opt = NoamOpt(dim_model, 1, 4000,
+                        T.optim.Adam(model.parameters(), lr=1e-3,
+                                     betas=(0.9, 0.98), eps=1e-9))
+
+    # Train & evaluate
     for epoch in range(100):
-        train_iter = dataset(graph_pool, mode='train', batch_size=args.batch, devices=devices)
-        valid_iter = dataset(graph_pool, mode='valid', batch_size=args.batch, devices=devices)
-        print('Epoch: {} Training...'.format(epoch))
+        start = time.time()
+        train_iter = dataset(graph_pool, mode='train', batch_size=args.batch,
+                             device=device, dev_rank=dev_rank, ndev=ndev)
         model.train(True)
-        run_epoch(train_iter, model,
-                      loss_compute(criterion, model_opt), is_train=True)
-        print('Epoch: {} Evaluating...'.format(epoch))
-        model.att_weight_map = None
-        model.eval()
-        run_epoch(valid_iter, model,
-                      loss_compute(criterion, None), is_train=False)
-        # Visualize attention
-        if args.viz:
-            src_seq = dataset.get_seq_by_id(VIZ_IDX, mode='valid', field='src')
-            tgt_seq = dataset.get_seq_by_id(VIZ_IDX, mode='valid', field='tgt')[:-1]
-            draw_atts(model.att_weight_map, src_seq, tgt_seq, exp_setting, 'epoch_{}'.format(epoch))
+        run_epoch(epoch, train_iter, dev_rank, ndev, model,
+                  loss_compute(opt=model_opt), is_train=True)
+        if dev_rank == 0:
+            model.att_weight_map = None
+            model.eval()
+            valid_iter = dataset(graph_pool, mode='valid', batch_size=args.batch,
+                                 device=device, dev_rank=dev_rank, ndev=1)
+            run_epoch(epoch, valid_iter, dev_rank, 1, model,
+                      loss_compute(opt=None), is_train=False)
+            end = time.time()
+            print("epoch time: {}".format(end - start))
+
+            # Visualize attention
+            if args.viz:
+                src_seq = dataset.get_seq_by_id(VIZ_IDX, mode='valid', field='src')
+                tgt_seq = dataset.get_seq_by_id(VIZ_IDX, mode='valid', field='tgt')[:-1]
+                draw_atts(model.att_weight_map, src_seq, tgt_seq, exp_setting, 'epoch_{}'.format(epoch))
+            args_filter = ['batch', 'gpus', 'viz', 'master_ip', 'master_port', 'grad_accum', 'ngpu']
+            exp_setting = '-'.join('{}'.format(v) for k, v in vars(args).items() if k not in args_filter)
+            with open('checkpoints/{}-{}.pkl'.format(exp_setting, epoch), 'wb') as f:
+                torch.save(model.state_dict(), f)
+
+if __name__ == '__main__':
+    if not os.path.exists('checkpoints'):
+        os.makedirs('checkpoints')
+    np.random.seed(1111)
+    argparser = argparse.ArgumentParser('training translation model')
+    argparser.add_argument('--gpus', default='-1', type=str, help='gpu id')
+    argparser.add_argument('--N', default=6, type=int, help='enc/dec layers')
+    argparser.add_argument('--dataset', default='multi30k', help='dataset')
+    argparser.add_argument('--batch', default=128, type=int, help='batch size')
+    argparser.add_argument('--viz', action='store_true',
+                           help='visualize attention')
+    argparser.add_argument('--universal', action='store_true',
+                           help='use universal transformer')
+    argparser.add_argument('--master-ip', type=str, default='127.0.0.1',
+                           help='master ip address')
+    argparser.add_argument('--master-port', type=str, default='12345',
+                           help='master port')
+    argparser.add_argument('--grad-accum', type=int, default=1,
+                           help='accumulate gradients for this many times '
+                                'then update weights')
+    args = argparser.parse_args()
+    print(args)
 
-        print('----------------------------------')
-        with open('checkpoints/{}-{}.pkl'.format(exp_setting, epoch), 'wb') as f:
-            th.save(model.state_dict(), f)
+    devices = list(map(int, args.gpus.split(',')))
+    if len(devices) == 1:
+        args.ngpu = 0 if devices[0] < 0 else 1
+        main(devices[0], args)
+    else:
+        args.ngpu = len(devices)
+        mp = torch.multiprocessing.get_context('spawn')
+        procs = []
+        for dev_id in devices:
+            procs.append(mp.Process(target=run, args=(dev_id, args),
+                                    daemon=True))
+            procs[-1].start()
+        for p in procs:
+            p.join()