gunzip.m is very slow

Question

Apri in MATLAB Online

0 voti

I am running MATLAB 2010b, win7, 64 bit, quod core, 16GB RAM.

I have a large number of csv.gz files, between 200MB and 6GB in size on my local drive.

myPathData = C:\myFile.csv.gz

I need to extract the file. using tic/toc, for a 200MB file

f = char(gunzip(myPathData));

the time taken is 152 minutes!

This is too slow for me.

I can manually extract the file using WINRAR in 13 mins. I try and call winrar from MATLAB but it fails:

cd('C:\Program Files\WinRAR\');
[status,result] = system(['UnRAR.exe' ' ' 'e' ' ' myPathData]); 
cd('V:\MatlabCode');

with the error message "csv.gz is not RAR archive" and "No files to extract".

I see the problem has also been posed here:

http://stackoverflow.com/questions/2295312/what-is-the-fastest-way-to-unzip-textfiles-in-matlab-during-a-function

Does anyone know how I can dramatically speed up the unzipping? (My only thought is to write something in C# (like below) and then call that exe from system.m). Surely there is a better way?

Many Thanks!

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.IO.Compression;
namespace ohMyGodICantBelieveIt
{
    public class unzipper
    {
          //http://msdn.microsoft.com/en-us/library/system.io.compression.gzipstream.aspx
          public static void Decompress(FileInfo fi)
          {
              // Get the stream of the source file.
              using (FileStream inFile = fi.OpenRead())
              {
                  // Get original file extension, for example "doc" from report.doc.gz.
                  string curFile = fi.FullName;
                  string origName = curFile.Remove(curFile.Length - fi.Extension.Length);
                  //Create the decompressed file.
                  using (FileStream outFile = File.Create(origName))
                  {
                      using (GZipStream Decompress = new GZipStream(inFile, CompressionMode.Decompress))
                      {
                          // Copy the decompression stream into the output file.
                          Decompress.CopyTo(outFile);
                      }
                  }
              }
          }
       }
  }