Update DDP for torch.distributed.run with gloo backend

train.py

@@ -37,15 +37,17 @@
 from utils.wandb_logging.wandb_utils import WandbLogger, check_wandb_resume
 
 logger = logging.getLogger(__name__)
+LOCAL_RANK = int(os.getenv('LOCAL_RANK', -1))  # https://pytorch.org/docs/stable/elastic/run.html
+RANK = int(os.getenv('RANK', -1))
+WORLD_SIZE = int(os.getenv('WORLD_SIZE', 1))
 
 
 def train(hyp,  # path/to/hyp.yaml or hyp dictionary
           opt,
           device,
           ):
-    save_dir, epochs, batch_size, total_batch_size, weights, rank, single_cls = \
-        Path(opt.save_dir), opt.epochs, opt.batch_size, opt.total_batch_size, opt.weights, opt.global_rank, \
-        opt.single_cls
+    save_dir, epochs, batch_size, total_batch_size, weights, single_cls = \
+        Path(opt.save_dir), opt.epochs, opt.batch_size, opt.total_batch_size, opt.weights, opt.single_cls
 
     # Directories
     wdir = save_dir / 'weights'
@@ -69,13 +71,13 @@ def train(hyp,  # path/to/hyp.yaml or hyp dictionary
     # Configure
     plots = not opt.evolve  # create plots
     cuda = device.type != 'cpu'
-    init_seeds(2 + rank)
+    init_seeds(2 + RANK)
     with open(opt.data) as f:
         data_dict = yaml.safe_load(f)  # data dict
 
     # Loggers
     loggers = {'wandb': None, 'tb': None}  # loggers dict
-    if rank in [-1, 0]:
+    if RANK in [-1, 0]:
         # TensorBoard
         if not opt.evolve:
             prefix = colorstr('tensorboard: ')
@@ -99,7 +101,7 @@ def train(hyp,  # path/to/hyp.yaml or hyp dictionary
     # Model
     pretrained = weights.endswith('.pt')
     if pretrained:
-        with torch_distributed_zero_first(rank):
+        with torch_distributed_zero_first(RANK):
             weights = attempt_download(weights)  # download if not found locally
         ckpt = torch.load(weights, map_location=device)  # load checkpoint
         model = Model(opt.cfg or ckpt['model'].yaml, ch=3, nc=nc, anchors=hyp.get('anchors')).to(device)  # create
@@ -110,7 +112,7 @@ def train(hyp,  # path/to/hyp.yaml or hyp dictionary
         logger.info('Transferred %g/%g items from %s' % (len(state_dict), len(model.state_dict()), weights))  # report
     else:
         model = Model(opt.cfg, ch=3, nc=nc, anchors=hyp.get('anchors')).to(device)  # create
-    with torch_distributed_zero_first(rank):
+    with torch_distributed_zero_first(RANK):
         check_dataset(data_dict)  # check
     train_path = data_dict['train']
     test_path = data_dict['val']
@@ -158,7 +160,7 @@ def train(hyp,  # path/to/hyp.yaml or hyp dictionary
     # plot_lr_scheduler(optimizer, scheduler, epochs)
 
     # EMA
-    ema = ModelEMA(model) if rank in [-1, 0] else None
+    ema = ModelEMA(model) if RANK in [-1, 0] else None
 
     # Resume
     start_epoch, best_fitness = 0, 0.0
@@ -194,28 +196,28 @@ def train(hyp,  # path/to/hyp.yaml or hyp dictionary
     imgsz, imgsz_test = [check_img_size(x, gs) for x in opt.img_size]  # verify imgsz are gs-multiples
 
     # DP mode
-    if cuda and rank == -1 and torch.cuda.device_count() > 1:
+    if cuda and RANK == -1 and torch.cuda.device_count() > 1:
         model = torch.nn.DataParallel(model)
 
     # SyncBatchNorm
-    if opt.sync_bn and cuda and rank != -1:
+    if opt.sync_bn and cuda and RANK != -1:
         model = torch.nn.SyncBatchNorm.convert_sync_batchnorm(model).to(device)
         logger.info('Using SyncBatchNorm()')
 
     # Trainloader
     dataloader, dataset = create_dataloader(train_path, imgsz, batch_size, gs, single_cls,
-                                            hyp=hyp, augment=True, cache=opt.cache_images, rect=opt.rect, rank=rank,
-                                            world_size=opt.world_size, workers=opt.workers,
+                                            hyp=hyp, augment=True, cache=opt.cache_images, rect=opt.rect, rank=RANK,
+                                            workers=opt.workers,
                                             image_weights=opt.image_weights, quad=opt.quad, prefix=colorstr('train: '))
     mlc = np.concatenate(dataset.labels, 0)[:, 0].max()  # max label class
     nb = len(dataloader)  # number of batches
     assert mlc < nc, 'Label class %g exceeds nc=%g in %s. Possible class labels are 0-%g' % (mlc, nc, opt.data, nc - 1)
 
     # Process 0
-    if rank in [-1, 0]:
+    if RANK in [-1, 0]:
         testloader = create_dataloader(test_path, imgsz_test, batch_size * 2, gs, single_cls,
                                        hyp=hyp, cache=opt.cache_images and not opt.notest, rect=True, rank=-1,
-                                       world_size=opt.world_size, workers=opt.workers,
+                                       workers=opt.workers,
                                        pad=0.5, prefix=colorstr('val: '))[0]
 
         if not opt.resume:
@@ -234,8 +236,8 @@ def train(hyp,  # path/to/hyp.yaml or hyp dictionary
             model.half().float()  # pre-reduce anchor precision
 
     # DDP mode
-    if cuda and rank != -1:
-        model = DDP(model, device_ids=[opt.local_rank], output_device=opt.local_rank,
+    if cuda and RANK != -1:
+        model = DDP(model, device_ids=[LOCAL_RANK], output_device=LOCAL_RANK,
                     # nn.MultiheadAttention incompatibility with DDP https://github.com/pytorch/pytorch/issues/26698
                     find_unused_parameters=any(isinstance(layer, nn.MultiheadAttention) for layer in model.modules()))
 
@@ -269,27 +271,27 @@ def train(hyp,  # path/to/hyp.yaml or hyp dictionary
         # Update image weights (optional)
         if opt.image_weights:
             # Generate indices
-            if rank in [-1, 0]:
+            if RANK in [-1, 0]:
                 cw = model.class_weights.cpu().numpy() * (1 - maps) ** 2 / nc  # class weights
                 iw = labels_to_image_weights(dataset.labels, nc=nc, class_weights=cw)  # image weights
                 dataset.indices = random.choices(range(dataset.n), weights=iw, k=dataset.n)  # rand weighted idx
             # Broadcast if DDP
-            if rank != -1:
-                indices = (torch.tensor(dataset.indices) if rank == 0 else torch.zeros(dataset.n)).int()
+            if RANK != -1:
+                indices = (torch.tensor(dataset.indices) if RANK == 0 else torch.zeros(dataset.n)).int()
                 dist.broadcast(indices, 0)
-                if rank != 0:
+                if RANK != 0:
                     dataset.indices = indices.cpu().numpy()
 
         # Update mosaic border
         # b = int(random.uniform(0.25 * imgsz, 0.75 * imgsz + gs) // gs * gs)
         # dataset.mosaic_border = [b - imgsz, -b]  # height, width borders
 
         mloss = torch.zeros(4, device=device)  # mean losses
-        if rank != -1:
+        if RANK != -1:
             dataloader.sampler.set_epoch(epoch)
         pbar = enumerate(dataloader)
         logger.info(('\n' + '%10s' * 8) % ('Epoch', 'gpu_mem', 'box', 'obj', 'cls', 'total', 'labels', 'img_size'))
-        if rank in [-1, 0]:
+        if RANK in [-1, 0]:
             pbar = tqdm(pbar, total=nb)  # progress bar
         optimizer.zero_grad()
         for i, (imgs, targets, paths, _) in pbar:  # batch -------------------------------------------------------------
@@ -319,8 +321,8 @@ def train(hyp,  # path/to/hyp.yaml or hyp dictionary
             with amp.autocast(enabled=cuda):
                 pred = model(imgs)  # forward
                 loss, loss_items = compute_loss(pred, targets.to(device))  # loss scaled by batch_size
-                if rank != -1:
-                    loss *= opt.world_size  # gradient averaged between devices in DDP mode
+                if RANK != -1:
+                    loss *= WORLD_SIZE  # gradient averaged between devices in DDP mode
                 if opt.quad:
                     loss *= 4.
 
@@ -336,7 +338,7 @@ def train(hyp,  # path/to/hyp.yaml or hyp dictionary
                     ema.update(model)
 
             # Print
-            if rank in [-1, 0]:
+            if RANK in [-1, 0]:
                 mloss = (mloss * i + loss_items) / (i + 1)  # update mean losses
                 mem = '%.3gG' % (torch.cuda.memory_reserved() / 1E9 if torch.cuda.is_available() else 0)  # (GB)
                 s = ('%10s' * 2 + '%10.4g' * 6) % (
@@ -362,7 +364,7 @@ def train(hyp,  # path/to/hyp.yaml or hyp dictionary
         scheduler.step()
 
         # DDP process 0 or single-GPU
-        if rank in [-1, 0]:
+        if RANK in [-1, 0]:
             # mAP
             ema.update_attr(model, include=['yaml', 'nc', 'hyp', 'gr', 'names', 'stride', 'class_weights'])
             final_epoch = epoch + 1 == epochs
@@ -424,7 +426,7 @@ def train(hyp,  # path/to/hyp.yaml or hyp dictionary
 
         # end epoch ----------------------------------------------------------------------------------------------------
     # end training -----------------------------------------------------------------------------------------------------
-    if rank in [-1, 0]:
+    if RANK in [-1, 0]:
         logger.info(f'{epoch - start_epoch + 1} epochs completed in {(time.time() - t0) / 3600:.3f} hours.\n')
         if plots:
             plot_results(save_dir=save_dir)  # save as results.png
@@ -486,7 +488,6 @@ def train(hyp,  # path/to/hyp.yaml or hyp dictionary
     parser.add_argument('--single-cls', action='store_true', help='train multi-class data as single-class')
     parser.add_argument('--adam', action='store_true', help='use torch.optim.Adam() optimizer')
     parser.add_argument('--sync-bn', action='store_true', help='use SyncBatchNorm, only available in DDP mode')
-    parser.add_argument('--local_rank', type=int, default=-1, help='DDP parameter, do not modify')
     parser.add_argument('--workers', type=int, default=8, help='maximum number of dataloader workers')
     parser.add_argument('--project', default='runs/train', help='save to project/name')
     parser.add_argument('--entity', default=None, help='W&B entity')
@@ -501,11 +502,8 @@ def train(hyp,  # path/to/hyp.yaml or hyp dictionary
     parser.add_argument('--artifact_alias', type=str, default="latest", help='version of dataset artifact to be used')
     opt = parser.parse_args()
 
-    # Set DDP variables
-    opt.world_size = int(getattr(os.environ, 'WORLD_SIZE', 1))
-    opt.global_rank = int(getattr(os.environ, 'RANK', -1))
-    set_logging(opt.global_rank)
-    if opt.global_rank in [-1, 0]:
+    set_logging(RANK)
+    if RANK in [-1, 0]:
         check_git_status()
         check_requirements(exclude=['thop'])
 
@@ -514,11 +512,9 @@ def train(hyp,  # path/to/hyp.yaml or hyp dictionary
     if opt.resume and not wandb_run:  # resume an interrupted run
         ckpt = opt.resume if isinstance(opt.resume, str) else get_latest_run()  # specified or most recent path
         assert os.path.isfile(ckpt), 'ERROR: --resume checkpoint does not exist'
-        apriori = opt.global_rank, opt.local_rank
         with open(Path(ckpt).parent.parent / 'opt.yaml') as f:
             opt = argparse.Namespace(**yaml.safe_load(f))  # replace
-        opt.cfg, opt.weights, opt.resume, opt.batch_size, opt.global_rank, opt.local_rank = \
-            '', ckpt, True, opt.total_batch_size, *apriori  # reinstate
+        opt.cfg, opt.weights, opt.resume, opt.batch_size = '', ckpt, True, opt.total_batch_size  # reinstate
         logger.info('Resuming training from %s' % ckpt)
     else:
         # opt.hyp = opt.hyp or ('hyp.finetune.yaml' if opt.weights else 'hyp.scratch.yaml')
@@ -531,14 +527,15 @@ def train(hyp,  # path/to/hyp.yaml or hyp dictionary
     # DDP mode
     opt.total_batch_size = opt.batch_size
     device = select_device(opt.device, batch_size=opt.batch_size)
-    if opt.local_rank != -1:
-        assert torch.cuda.device_count() > opt.local_rank
-        torch.cuda.set_device(opt.local_rank)
-        device = torch.device('cuda', opt.local_rank)
-        dist.init_process_group(backend='nccl', init_method='env://')  # distributed backend
-        assert opt.batch_size % opt.world_size == 0, '--batch-size must be multiple of CUDA device count'
+    print({'RANK': RANK, 'LOCAL_RANK': LOCAL_RANK, 'WORLD_SIZE': WORLD_SIZE})
+    if LOCAL_RANK != -1:
+        assert torch.cuda.device_count() > LOCAL_RANK, 'too few GPUS for DDP command'
+        torch.cuda.set_device(LOCAL_RANK)
+        device = torch.device('cuda', LOCAL_RANK)
+        dist.init_process_group(backend="gloo")  # distributed backend
+        assert opt.batch_size % WORLD_SIZE == 0, '--batch-size must be multiple of CUDA device count'
         assert not opt.image_weights, '--image-weights argument is not compatible with DDP training'
-        opt.batch_size = opt.total_batch_size // opt.world_size
+        opt.batch_size = opt.total_batch_size // WORLD_SIZE
 
     # Train
     logger.info(opt)
@@ -579,7 +576,7 @@ def train(hyp,  # path/to/hyp.yaml or hyp dictionary
 
         with open(opt.hyp) as f:
             hyp = yaml.safe_load(f)  # load hyps dict
-        assert opt.local_rank == -1, 'DDP mode not implemented for --evolve'
+        assert LOCAL_RANK == -1, 'DDP mode not implemented for --evolve'
         opt.notest, opt.nosave = True, True  # only test/save final epoch
         # ei = [isinstance(x, (int, float)) for x in hyp.values()]  # evolvable indices
         yaml_file = Path(opt.save_dir) / 'hyp_evolved.yaml'  # save best result here

utils/datasets.py

@@ -64,7 +64,7 @@ def exif_size(img):
 
 
 def create_dataloader(path, imgsz, batch_size, stride, single_cls=False, hyp=None, augment=False, cache=False, pad=0.0,
-                      rect=False, rank=-1, world_size=1, workers=8, image_weights=False, quad=False, prefix=''):
+                      rect=False, rank=-1, workers=8, image_weights=False, quad=False, prefix=''):
     # Make sure only the first process in DDP process the dataset first, and the following others can use the cache
     with torch_distributed_zero_first(rank):
         dataset = LoadImagesAndLabels(path, imgsz, batch_size,
@@ -79,7 +79,7 @@ def create_dataloader(path, imgsz, batch_size, stride, single_cls=False, hyp=Non
                                       prefix=prefix)
 
     batch_size = min(batch_size, len(dataset))
-    nw = min([os.cpu_count() // world_size, batch_size if batch_size > 1 else 0, workers])  # number of workers
+    nw = min([os.cpu_count(), batch_size if batch_size > 1 else 0, workers])  # number of workers
     sampler = torch.utils.data.distributed.DistributedSampler(dataset) if rank != -1 else None
     loader = torch.utils.data.DataLoader if image_weights else InfiniteDataLoader
     # Use torch.utils.data.DataLoader() if dataset.properties will update during training else InfiniteDataLoader()

utils/wandb_logging/wandb_utils.py

@@ -1,5 +1,6 @@
 """Utilities and tools for tracking runs with Weights & Biases."""
 import logging
+import os
 import sys
 from contextlib import contextmanager
 from pathlib import Path
@@ -18,6 +19,7 @@
 except ImportError:
     wandb = None
 
+RANK = int(os.getenv('RANK', -1))
 WANDB_ARTIFACT_PREFIX = 'wandb-artifact://'
 
 
@@ -42,10 +44,10 @@ def get_run_info(run_path):
 
 
 def check_wandb_resume(opt):
-    process_wandb_config_ddp_mode(opt) if opt.global_rank not in [-1, 0] else None
+    process_wandb_config_ddp_mode(opt) if RANK not in [-1, 0] else None
     if isinstance(opt.resume, str):
         if opt.resume.startswith(WANDB_ARTIFACT_PREFIX):
-            if opt.global_rank not in [-1, 0]:  # For resuming DDP runs
+            if RANK not in [-1, 0]:  # For resuming DDP runs
                 entity, project, run_id, model_artifact_name = get_run_info(opt.resume)
                 api = wandb.Api()
                 artifact = api.artifact(entity + '/' + project + '/' + model_artifact_name + ':latest')