title: LMDB files and how they are used for caffe deep learning network
body: <p>I am quite new in deep learning and I am having some problems in using the caffe deep learning network. Basically, I didn't find any documentation explaining how I can solve a series of questions and problems I am dealing right now.</p>
  
  <p>Please, let me explain my situation first. </p>
  
  <p>I have thousands of images and I must do a series of pre-processing operations on them. For each pre-processing operation, I have to save these pre-processed images as 4D matrices and also store a vector with the images labels. I will store this information as LMDB files that will be used as input for the caffe googlenet deep learning. </p>
  
  <p>I tried to save my images as .HD5 files, but the final file size is 80GB, which is impossible to process with the memory I have.</p>
  
  <p>So, the other option is using LMDB files, right? I am quite newbie in this file format and I appreciate your help in understanding how to create them in Matlab. Basically, my rookie questions are: </p>
  
  <p>1- These LMDB files have extension .MDB, right? is this extension the same used by microsoft access? or the right format is .lmdb and they are different? </p>
  
  <p>2- I find this solution for creating .mdb files (<a href="https://github.com/kyamagu/matlab-leveldb" rel="noreferrer">https://github.com/kyamagu/matlab-leveldb</a>), does it create the file format needed by caffe?</p>
  
  <p>3- For caffe, should I have to create one .mdb file for labels and other for images or both can be fields of the same .mdb file?</p>
  
  <p>4- When I create an .mdb file I have to label the database fields. Can I label one field as image and other as label? does caffe understand which field means?</p>
  
  <p>5- what does the function (in <a href="https://github.com/kyamagu/matlab-leveldb" rel="noreferrer">https://github.com/kyamagu/matlab-leveldb</a>) database.put('key1', 'value1') and database.put('key2', 'value2') do? Should I have to save my 4-d matrices in one field and the label vector in another?</p>