Training speed of mxnet-ssd slows down?

[nopattern]

 I have use record file(voc07+12) to train old-style ssd at a speed of 40 images/s ,The speed is about 25 images/s when  I try the new  train_ssd.py in gluoncv.
 I use rec dataset and  transform to replace origin file datasets in new ssd code. But when I set **num-workers=4** the gdata.DetectionDataLoader  failed ,while **num-workers=1** , It works but the speed is almost as  slow as original data reading method.
The  error infomation is as following:

Process Process-3:
Traceback (most recent call last):
  File "/usr/lib/python2.7/multiprocessing/process.py", line 258, in _bootstrap
  File "/usr/lib/python2.7/multiprocessing/process.py", line 258, in _bootstrap
    self.run()
  File "/usr/lib/python2.7/multiprocessing/process.py", line 114, in run
    self._target(*self._args, **self._kwargs)
  File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/gluon/data/dataloader.py", line 134, in worker_loop
    batch = batchify_fn([dataset[i] for i in samples])
  File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/gluon/data/dataset.py", line 126, in __getitem__
    self.run()
    item = self._data[idx]
  File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/gluon/data/vision/datasets.py", line 257, in __getitem__
  File "/usr/lib/python2.7/multiprocessing/process.py", line 114, in run
    record = super(ImageRecordDataset, self).__getitem__(idx)
  File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/gluon/data/dataset.py", line 180, in __getitem__
    return self._record.read_idx(self._record.keys[idx])
  File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/recordio.py", line 265, in read_idx
    self._target(*self._args, **self._kwargs)
  File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/gluon/data/dataloader.py", line 134, in worker_loop
    return self.read()
  File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/recordio.py", line 163, in read
    ctypes.byref(size)))
  File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/base.py", line 149, in check_call
    batch = batchify_fn([dataset[i] for i in samples])
    raise MXNetError(py_str(_LIB.MXGetLastError()))
MXNetError: [16:12:48] src/recordio.cc:65: Check failed: header[0] == RecordIOWriter::kMagic Invalid RecordIO File

It seems a multi-process problem with old rec file dataset?

[zhreshold]

Can you elaborate how do you use record file with gluon data loader?
Did you check out this one which is added recently: https://github.com/dmlc/gluon-cv/blob/master/gluoncv/data/recordio/detection.py

[nopattern]

  I added a dataset transform function

 def old_rec_2_new(rec_old):
   """ rec_old  , [2,6, cls_id, xmin, ymin, xmax, ymax,  difficult.....]
       rec_new  , [[xmin, ymin, xmax, ymax, cls_id, difficult],]
   """
   label_width = int(rec_old[1])
   obj_num = (rec_old.shape[0]-2)/label_width
   rec_new = np.zeros((obj_num,label_width))
   offset = 2
   for i  in range(obj_num):
       rec_new[i][0:4] = rec_old[offset+1:offset+5]
       rec_new[i][4] = rec_old[offset]
       rec_new[i][5] = rec_old[offset+5]

       offset += label_width

   return rec_new

and read recordiofile ,

 def get_dataset_rec(dataset):
    data_dir='./data/'
    
    train_dataset = ImageRecordDataset(data_dir+'train.rec',transform=rec_old2_new_transform)
    val_dataset = ImageRecordDataset(data_dir+'val.rec',transform=rec_old2_new_transform)
    
    return train_dataset,val_dataset 

I pull the new code , change the function to use RecordFileDetection,

def get_dataset_rec(dataset):
    data_dir='./data/'
    
    train_dataset = RecordFileDetection(data_dir+'train.rec')
    val_dataset = RecordFileDetection(data_dir+'val.rec')
    
    return train_dataset,val_dataset

The error info is ,

[09:09:14] src/operator/nn/./cudnn/./cudnn_algoreg-inl.h:107: Running performance tests to find the best convolution algorithm, this can take a while... (setting env variable MXNET_CUDNN_AUTOTUNE_DEFAULT to 0 to disable)
Traceback (most recent call last):
File "train_ssd.py", line 238, in
train(net, train_data, val_data, classes, args)
File "train_ssd.py", line 182, in train
autograd.backward(sum_loss)
File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/autograd.py", line 267, in backward
ctypes.c_void_p(0)))
File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/base.py", line 149, in check_call
raise MXNetError(py_str(_LIB.MXGetLastError()))
mxnet.base.MXNetError: [09:09:22] src/imperative/imperative.cc:373: Check failed: !AGInfo::IsNone(*i) Cannot differentiate node because it is not in a computational graph. You need to set is_recording to true or use autograd.record() to save computational graphs for backward. If you want to differentiate the same graph twice, you need to pass retain_graph=True to backward.

Stack trace returned 10 entries:
[bt] (0) /home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/../../lib/libmxnet.so(dmlc::StackTraceabi:cxx11+0x5b) [0x7fd6a6077b6b]
[bt] (1) /home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/../../lib/libmxnet.so(dmlc::LogMessageFatal::~LogMessageFatal()+0x28) [0x7fd6a60786d8]
[bt] (2) /home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/../../lib/libmxnet.so(mxnet::Imperative::Backward(std::vector<mxnet::NDArray*, std::allocatormxnet::NDArray* > const&, std::vector<mxnet::NDArray*, std::allocatormxnet::NDArray* > const&, std::vector<mxnet::NDArray*, std::allocatormxnet::NDArray* > const&, bool, bool, bool)+0x291) [0x7fd6a858ded1]
[bt] (3) /home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/../../lib/libmxnet.so(MXAutogradBackwardEx+0x9a8) [0x7fd6a893aae8]
[bt] (4) /usr/lib/x86_64-linux-gnu/libffi.so.6(ffi_call_unix64+0x4c) [0x7fd6b6514e40]
[bt] (5) /usr/lib/x86_64-linux-gnu/libffi.so.6(ffi_call+0x2eb) [0x7fd6b65148ab]
[bt] (6) /usr/lib/python2.7/lib-dynload/_ctypes.x86_64-linux-gnu.so(_ctypes_callproc+0x48f) [0x7fd6b67243df]
[bt] (7) /usr/lib/python2.7/lib-dynload/_ctypes.x86_64-linux-gnu.so(+0x11d82) [0x7fd6b6728d82]
[bt] (8) python(PyObject_Call+0x43) [0x4b0c93]
[bt] (9) python(PyEval_EvalFrameEx+0x602f) [0x4c9f9f]

[zhreshold]

The latest error seems to be unrelated to data loader, did you changed the network training part?

[nopattern]

sorry ,The error before may be caused by gluoncv not updated correctly. I updated gluoncv again and the error is as following,

Corrupt JPEG data: premature end of data segment
Process Process-4:
Process Process-2:
Traceback (most recent call last):
Traceback (most recent call last):
File "/usr/lib/python2.7/multiprocessing/process.py", line 258, in _bootstrap
File "/usr/lib/python2.7/multiprocessing/process.py", line 258, in _bootstrap
self.run()
self.run()
File "/usr/lib/python2.7/multiprocessing/process.py", line 114, in run
File "/usr/lib/python2.7/multiprocessing/process.py", line 114, in run
self._target(*self._args, **self._kwargs)
self._target(*self._args, **self._kwargs)
File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/gluon/data/dataloader.py", line 134, in worker_loop
File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/gluon/data/dataloader.py", line 134, in worker_loop
batch = batchify_fn([dataset[i] for i in samples])
batch = batchify_fn([dataset[i] for i in samples])
File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/gluon/data/dataset.py", line 126, in getitem
File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/gluon/data/dataset.py", line 126, in getitem
item = self._data[idx]
item = self._data[idx]
File "build/bdist.linux-x86_64/egg/gluoncv/data/recordio/detection.py", line 37, in getitem
File "build/bdist.linux-x86_64/egg/gluoncv/data/recordio/detection.py", line 37, in getitem
img, label = super(RecordFileDetection, self).getitem(idx)
img, label = super(RecordFileDetection, self).getitem(idx)
File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/gluon/data/vision/datasets.py", line 257, in getitem
File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/gluon/data/vision/datasets.py", line 257, in getitem
record = super(ImageRecordDataset, self).getitem(idx)
record = super(ImageRecordDataset, self).getitem(idx)
File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/gluon/data/dataset.py", line 180, in getitem
File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/gluon/data/dataset.py", line 180, in getitem
return self._record.read_idx(self._record.keys[idx])
return self._record.read_idx(self._record.keys[idx])
File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/recordio.py", line 265, in read_idx
File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/recordio.py", line 265, in read_idx
return self.read()
return self.read()
File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/recordio.py", line 163, in read
File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/recordio.py", line 163, in read
ctypes.byref(size)))
ctypes.byref(size)))
File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/base.py", line 149, in check_call
File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/base.py", line 149, in check_call
raise MXNetError(py_str(_LIB.MXGetLastError()))
raise MXNetError(py_str(_LIB.MXGetLastError()))
MXNetError: [12:09:26] src/recordio.cc:65: Check failed: header[0] == RecordIOWriter::kMagic Invalid RecordIO File

Stack trace returned 10 entries:
[bt] (0) /home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/../../lib/libmxnet.so(dmlc::StackTraceabi:cxx11+0x5b) [0x7fdc39641b6b]
[bt] (1) /home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/../../lib/libmxnet.so(dmlc::RecordIOReader::NextRecord(std::__cxx11::basic_string<char, std::char_traits, std::allocator >*)+0x6ec) [0x7fdc3bfe941c]
[bt] (2) /home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/../../lib/libmxnet.so(MXRecordIOReaderReadRecord+0x26) [0x7fdc3bf2e236]
[bt] (3) /usr/lib/x86_64-linux-gnu/libffi.so.6(ffi_call_unix64+0x4c) [0x7fdc49adee40]
[bt] (4) /usr/lib/x86_64-linux-gnu/libffi.so.6(ffi_call+0x2eb) [0x7fdc49ade8ab]
[bt] (5) /usr/lib/python2.7/lib-dynload/_ctypes.x86_64-linux-gnu.so(_ctypes_callproc+0x48f) [0x7fdc49cee3df]
[bt] (6) /usr/lib/python2.7/lib-dynload/_ctypes.x86_64-linux-gnu.so(+0x11d82) [0x7fdc49cf2d82]
[bt] (7) python(PyObject_Call+0x43) [0x4b0c93]
[bt] (8) python(PyEval_EvalFrameEx+0x602f) [0x4c9f9f]
[bt] (9) python(PyEval_EvalCodeEx+0x255) [0x4c2705]

[nopattern]

Try again:
The before error happened when I set num-workers = 1. The "Invalid RecordIO File "error happened when num-workers = 4.

[zhreshold]

Can you use num-workers=0 to disable multiprocessing and make sure the record file is good?

[zhreshold]

I suspect it might relate to multi-worker but cannot confirm.

[nopattern]

The record file is good because I have tested with my own transform with num-workers = 1 or num-workers= 0.
The output is as following when setting num-workers = 0 and using RecordFileDetection,

Traceback (most recent call last):
File "train_ssd.py", line 271, in
train(net, train_data, val_data, classes, args)
File "train_ssd.py", line 214, in train
autograd.backward(sum_loss)
File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/autograd.py", line 267, in backward
ctypes.c_void_p(0)))
File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/base.py", line 149, in check_call
raise MXNetError(py_str(_LIB.MXGetLastError()))
mxnet.base.MXNetError: [07:37:51] src/imperative/imperative.cc:373: Check failed: !AGInfo::IsNone(*i) Cannot differentiate node because it is not in a computational graph. You need to set is_recording to true or use autograd.record() to save computational graphs for backward. If you want to differentiate the same graph twice, you need to pass retain_graph=True to backward.

Stack trace returned 10 entries:
[bt] (0) /home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/../../lib/libmxnet.so(dmlc::StackTraceabi:cxx11+0x5b) [0x7f8bfe309b6b]
[bt] (1) /home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/../../lib/libmxnet.so(dmlc::LogMessageFatal::~LogMessageFatal()+0x28) [0x7f8bfe30a6d8]
[bt] (2) /home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/../../lib/libmxnet.so(mxnet::Imperative::Backward(std::vector<mxnet::NDArray*, std::allocatormxnet::NDArray* > const&, std::vector<mxnet::NDArray*, std::allocatormxnet::NDArray* > const&, std::vector<mxnet::NDArray*, std::allocatormxnet::NDArray* > const&, bool, bool, bool)+0x291) [0x7f8c0081fed1]
[bt] (3) /home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/../../lib/libmxnet.so(MXAutogradBackwardEx+0x9a8) [0x7f8c00bccae8]
[bt] (4) /usr/lib/x86_64-linux-gnu/libffi.so.6(ffi_call_unix64+0x4c) [0x7f8c0e7a6e40]
[bt] (5) /usr/lib/x86_64-linux-gnu/libffi.so.6(ffi_call+0x2eb) [0x7f8c0e7a68ab]
[bt] (6) /usr/lib/python2.7/lib-dynload/_ctypes.x86_64-linux-gnu.so(_ctypes_callproc+0x48f) [0x7f8c0e9b63df]
[bt] (7) /usr/lib/python2.7/lib-dynload/_ctypes.x86_64-linux-gnu.so(+0x11d82) [0x7f8c0e9bad82]
[bt] (8) python(PyObject_Call+0x43) [0x4b0c93]
[bt] (9) python(PyEval_EvalFrameEx+0x602f) [0x4c9f9f]

[zhreshold]

I am confused. Can you post your training script?

[nopattern]

OK, but I haven't change training script:

def train(net, train_data, val_data, classes, args):
   """Training pipeline"""
   net.collect_params().reset_ctx(ctx)
   trainer = gluon.Trainer(
       net.collect_params(), 'sgd',
       {'learning_rate': args.lr, 'wd': args.wd, 'momentum': args.momentum})

   # lr decay policy
   lr_decay = float(args.lr_decay)
   lr_steps = sorted([float(ls) for ls in args.lr_decay_epoch.split(',') if ls.strip()])

   mbox_loss = gcv.loss.SSDMultiBoxLoss()
   ce_metric = mx.metric.Loss('CrossEntropy')
   smoothl1_metric = mx.metric.Loss('SmoothL1')

   # set up logger
   logging.basicConfig()
   logger = logging.getLogger()
   logger.setLevel(logging.INFO)
   log_file_path = args.save_prefix + '_train.log'
   log_dir = os.path.dirname(log_file_path)
   if log_dir and not os.path.exists(log_dir):
       os.makedirs(log_dir)
   fh = logging.FileHandler(log_file_path)
   logger.addHandler(fh)
   logger.info(args)
   logger.info('Start training from [Epoch %d]' % args.start_epoch)
   best_map = [0]
   for epoch in range(args.start_epoch, args.epochs):
       while lr_steps and epoch >= lr_steps[0]:
           new_lr = trainer.learning_rate * lr_decay
           lr_steps.pop(0)
           trainer.set_learning_rate(new_lr)
           logger.info("[Epoch {}] Set learning rate to {}".format(epoch, new_lr))
       ce_metric.reset()
       smoothl1_metric.reset()
       tic = time.time()
       btic = time.time()
       net.hybridize()
       for i, batch in enumerate(train_data):
           batch_size = batch[0].shape[0]
           data = gluon.utils.split_and_load(batch[0], ctx_list=ctx, batch_axis=0)
           cls_targets = gluon.utils.split_and_load(batch[1], ctx_list=ctx, batch_axis=0)
           box_targets = gluon.utils.split_and_load(batch[2], ctx_list=ctx, batch_axis=0)
           with autograd.record():
               cls_preds = []
               box_preds = []
               for x in data:
                   cls_pred, box_pred, _ = net(x)
                   cls_preds.append(cls_pred)
                   box_preds.append(box_pred)
               sum_loss, cls_loss, box_loss = mbox_loss(
                   cls_preds, box_preds, cls_targets, box_targets)
               autograd.backward(sum_loss)
           # since we have already normalized the loss, we don't want to normalize
           # by batch-size anymore
           trainer.step(1)
           ce_metric.update(0, [l * batch_size for l in cls_loss])
           smoothl1_metric.update(0, [l * batch_size for l in box_loss])
           if args.log_interval and not (i + 1) % args.log_interval:
               name1, loss1 = ce_metric.get()
               name2, loss2 = smoothl1_metric.get()
               logger.info('[Epoch %d][Batch %d], Speed: %f samples/sec, %s=%f, %s=%f'%(
                   epoch, i, batch_size/(time.time()-btic), name1, loss1, name2, loss2))
           btic = time.time()

       name1, loss1 = ce_metric.get()
       name2, loss2 = smoothl1_metric.get()
       logger.info('[Epoch %d] Training cost: %f, %s=%f, %s=%f'%(
           epoch, (time.time()-tic), name1, loss1, name2, loss2))
       map_name, mean_ap = validate(net, val_data, ctx, classes)
       val_msg = '\n'.join(['%s=%f'%(k, v) for k, v in zip(map_name, mean_ap)])
       logger.info('[Epoch %d] Validation: \n%s'%(epoch, val_msg))
       save_params(net, best_map, mean_ap[-1], epoch, args.save_interval, args.save_prefix)

I writed the classes directly in main function :

if __name__ == '__main__':
    
    CLASSES = ('aeroplane', 'bicycle', 'bird', 'boat', 'bottle', 'bus', 'car',
               'cat', 'chair', 'cow', 'diningtable', 'dog', 'horse', 'motorbike',
               'person', 'pottedplant', 'sheep', 'sofa', 'train', 'tvmonitor')
               
    args = parse_args()
    # fix seed for mxnet, numpy and python builtin random generator.
    gutils.random.seed(args.seed)

    # training contexts
    ctx = [mx.gpu(int(i)) for i in args.gpus.split(',') if i.strip()]
    ctx = ctx if ctx else [mx.cpu()]

    # network
    net_name = '_'.join(('ssd', str(args.data_shape), args.network, args.dataset))
    net = get_model(net_name, pretrained_base=True)
    if args.resume.strip():
        net.load_params(args.resume.strip())
    else:
        for param in net.collect_params().values():
            if param._data is not None:
                continue
            param.initialize()

    # training data
    #train_dataset, val_dataset = get_dataset(args.dataset)
    #train_dataset, val_dataset = get_dataset_rec(args.dataset)
    train_dataset, val_dataset = get_dataset_rec_me(args.dataset)
    train_data, val_data = get_dataloader(
        net, train_dataset, val_dataset, args.data_shape, args.batch_size, args.num_workers)
    classes = CLASSES#train_dataset.classes  # class names

    # training
    args.save_prefix += net_name
    train(net, train_data, val_data, classes, args)

[nopattern]

@zhreshold The previous error occured because I have change position format from float to int(original ,not normalized) in record file for my transformer. sorry .
Now I restored record file in the original format .num-workers = 1 works. But the speed drops to 12image/s. num-workers = 4 dones't work .The output info,

Corrupt JPEG data: premature end of data segment
Corrupt JPEG data: premature end of data segment
Corrupt JPEG data: 40 extraneous bytes before marker 0xdb
Corrupt JPEG data: premature end of data segment
Process Process-2:
Traceback (most recent call last):
File "/usr/lib/python2.7/multiprocessing/process.py", line 258, in _bootstrap
self.run()
File "/usr/lib/python2.7/multiprocessing/process.py", line 114, in run
self._target(*self._args, **self._kwargs)
File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/gluon/data/dataloader.py", line 134, in worker_loop
batch = batchify_fn([dataset[i] for i in samples])
File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/gluon/data/dataset.py", line 126, in getitem
item = self._data[idx]
File "build/bdist.linux-x86_64/egg/gluoncv/data/recordio/detection.py", line 37, in getitem
img, label = super(RecordFileDetection, self).getitem(idx)
File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/gluon/data/vision/datasets.py", line 257, in getitem
record = super(ImageRecordDataset, self).getitem(idx)
File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/gluon/data/dataset.py", line 180, in getitem
return self._record.read_idx(self._record.keys[idx])
File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/recordio.py", line 265, in read_idx
return self.read()
File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/recordio.py", line 163, in read
ctypes.byref(size)))
File "/home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/base.py", line 149, in check_call
raise MXNetError(py_str(_LIB.MXGetLastError()))
MXNetError: [09:24:49] src/recordio.cc:65: Check failed: header[0] == RecordIOWriter::kMagic Invalid RecordIO File

Stack trace returned 10 entries:
[bt] (0) /home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/../../lib/libmxnet.so(dmlc::StackTraceabi:cxx11+0x5b) [0x7fe3e9440b6b]
[bt] (1) /home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/../../lib/libmxnet.so(dmlc::RecordIOReader::NextRecord(std::__cxx11::basic_string<char, std::char_traits, std::allocator >*)+0x6ec) [0x7fe3ebde841c]
[bt] (2) /home/deep/workssd/mxnet/incubator-mxnet/python/mxnet/../../lib/libmxnet.so(MXRecordIOReaderReadRecord+0x26) [0x7fe3ebd2d236]
[bt] (3) /usr/lib/x86_64-linux-gnu/libffi.so.6(ffi_call_unix64+0x4c) [0x7fe3f9a1ee40]
[bt] (4) /usr/lib/x86_64-linux-gnu/libffi.so.6(ffi_call+0x2eb) [0x7fe3f9a1e8ab]
[bt] (5) /usr/lib/python2.7/lib-dynload/_ctypes.x86_64-linux-gnu.so(_ctypes_callproc+0x48f) [0x7fe3f9c2e3df]
[bt] (6) /usr/lib/python2.7/lib-dynload/_ctypes.x86_64-linux-gnu.so(+0x11d82) [0x7fe3f9c32d82]
[bt] (7) python(PyObject_Call+0x43) [0x4b0c93]
[bt] (8) python(PyEval_EvalFrameEx+0x602f) [0x4c9f9f]
[bt] (9) python(PyEval_EvalCodeEx+0x255) [0x4c2705]

[zhreshold]

Tracked to apache/mxnet#9974

[nopattern]

@zhreshold
The latest version of gluoncv have installed and slows down the ssd training speed from about 25images/s to about 15images/s (unstable) , But your orginal mxnet-ssd is about 40 images/s !
It 's better to add expand image augment function in old ImageDetIter.

[WalterMa]

@zhreshold
According to your referenced issue, it isn't able to use RecordFileDetection in multi processing mode.
Am I right?

[zhreshold]

@WalterMa Yes, this bug should be easy to fix, but need to be careful not to change current api, so we are still discussing.

[zhreshold]

An temporary solution is added to RecordFileDetection so multi worker can be enabled.
I am closing this due to lack of activity. Feel free to ping me to reopen.