OSError: [Errno 12] Cannot allocate memory

[abhijeetnijampurkar]

After getting pretrain_detector evaluation results successfully, I received following: (with pred_stats.npy generated in data directory)
...
======================sgdet============================
R@20: 0.177577
R@50: 0.235745
R@100: 0.276802
0%| | 0/13223 [00:00<?, ?it/s]
Traceback (most recent call last):
File "models/eval_rel_count.py", line 180, in
for val_b, b in enumerate(tqdm(val_loader)):
File "/home/vplab/abhijeet/neural-motifs/venv/lib/python3.6/site-packages/tqdm/std.py", line 1081, in iter
for obj in iterable:
File "/home/vplab/abhijeet/neural-motifs/venv/lib/python3.6/site-packages/torch/utils/data/dataloader.py", line 417, in iter
return DataLoaderIter(self)
File "/home/vplab/abhijeet/neural-motifs/venv/lib/python3.6/site-packages/torch/utils/data/dataloader.py", line 234, in init
w.start()
File "/usr/lib/python3.6/multiprocessing/process.py", line 105, in start
self._popen = self._Popen(self)
File "/usr/lib/python3.6/multiprocessing/context.py", line 223, in _Popen
return _default_context.get_context().Process._Popen(process_obj)
File "/usr/lib/python3.6/multiprocessing/context.py", line 277, in _Popen
return Popen(process_obj)
File "/usr/lib/python3.6/multiprocessing/popen_fork.py", line 19, in init
self._launch(process_obj)
File "/usr/lib/python3.6/multiprocessing/popen_fork.py", line 66, in _launch
self.pid = os.fork()
OSError: [Errno 12] Cannot allocate memory
0%| | 0/13223 [00:01<?, ?it/s]

Please help me out, rectifying this problem.