Opened lmdb error: leading to "terminate called after throwing an instance of 'std::bad_alloc'?

[Kwot Sin Lee]

My error log gives me this:

I0807 11:30:00.214087  9808 db_lmdb.cpp:35] Opened lmdb /home/ubuntu/Desktop/caffe_tutorial/deeplearning-cats-dogs-tutorial/input/train_lmdb
terminate called after throwing an instance of 'std::bad_alloc'
  what():  std::bad_alloc
*** Aborted at 1470540600 (unix time) try "date -d @1470540600" if you are using GNU date ***
PC: @     0x7f2b7680c418 gsignal
*** SIGABRT (@0x3e800002649) received by PID 9801 (TID 0x7f2b4f839700) from PID 9801; stack trace: ***
    @     0x7f2b7680c4a0 (unknown)
    @     0x7f2b7680c418 gsignal
    @     0x7f2b7680e01a abort
    @     0x7f2b7761f84d __gnu_cxx::__verbose_terminate_handler()
    @     0x7f2b7761d6b6 (unknown)
    @     0x7f2b7761d701 std::terminate()
    @     0x7f2b7761d919 __cxa_throw
    @     0x7f2b7761debc operator new()
    @     0x7f2b787fdf1d std::__cxx11::basic_string<>::_M_construct<>()
    @     0x7f2b787fee2b _ZN5caffe2db10LMDBCursor5valueB5cxx11Ev
    @     0x7f2b7866ccbe caffe::DataReader::Body::read_one()
    @     0x7f2b7866d16d caffe::DataReader::Body::InternalThreadEntry()
    @     0x7f2b78666da5 caffe::InternalThread::entry()
    @     0x7f2b6e9245d5 (unknown)
    @     0x7f2b6e1d26fa start_thread
    @     0x7f2b768ddb5d clone
    @                0x0 (unknown)

However, my train_lmdb folder is in the correct place. Does this error appear because I have a wrong directory? In my train_lmdb folder, i have only 2 files : data.mdb and lock.mdb.