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Getting started with Torch

Installing Torch

We provide a simple installation process for Torch on Mac OS X and Ubuntu 12+:

Torch can be installed to your home folder in ~/torch by running these three commands:

# in a terminal, run the commands WITHOUT sudo
git clone ~/torch --recursive
cd ~/torch; bash install-deps;

The first script installs the basic package dependencies that LuaJIT and Torch require. The second script installs LuaJIT, LuaRocks, and then uses LuaRocks (the lua package manager) to install core packages like torch, nn and paths, as well as a few other packages.

The script adds torch to your PATH variable. You just have to source it once to refresh your env variables. The installation script will detect what is your current shell and modify the path in the correct configuration file.

# On Linux with bash
source ~/.bashrc
# On Linux with zsh
source ~/.zshrc
# On OSX or in Linux with none of the above.
source ~/.profile

If you ever need to uninstall torch, simply run the command:

rm -rf ~/torch

If you want to install torch with Lua 5.2 instead of LuaJIT, simply run:

git clone ~/torch --recursive
cd ~/torch

# clean old torch installation
# optional clean command (for older torch versions)
# curl -s | bash

# : set env to use lua

New packages can be installed using Luarocks from the command-line:

# run luarocks WITHOUT sudo
$ luarocks install image
$ luarocks list

Once installed you can run torch with the command th from you prompt!

The easiest way to learn and experiment with Torch is by starting an interactive session (also known as the torch read-eval-print loop or TREPL):

$ th
  ______             __   |  Torch7                                   
 /_  __/__  ________/ /   |  Scientific computing for Lua.         
  / / / _ \/ __/ __/ _ \  |                                           
 /_/  \___/_/  \__/_//_/  |   
th> torch.Tensor{1,2,3}
[torch.DoubleTensor of dimension 3]


To exit the interactive session, type ^c twice — the control key together with the c key, twice, or type os.exit(). Once the user has entered a complete expression, such as 1 + 2, and hits enter, the interactive session evaluates the expression and shows its value.

To evaluate expressions written in a source file file.lua, write dofile "file.lua".

To run code in a file non-interactively, you can give it as the first argument to the th command::

$ th file.lua

There are various ways to run Lua code and provide options, similar to those available for the perl and ruby programs:

 $ th -h
Usage: th [options] [script.lua [arguments]]

  -l name            load library name
  -e statement       execute statement
  -h,--help          print this help
  -a,--async         preload async (libuv) and start async repl (BETA)
  -g,--globals       monitor global variables (print a warning on creation/access)
  -gg,--gglobals     monitor global variables (throw an error on creation/access)
  -x,--gfx           start gfx server and load gfx env
  -i,--interactive   enter the REPL after executing a script

TREPL is full of convenient features likes:

  • Tab-completion on nested namespaces
  • Tab-completion on disk files (when opening a string)
  • History (preserved between sessions)
  • Pretty print (table introspection and coloring)
  • Auto-print after eval (can be stopped with ;)
  • Each command is profiled, timing is reported
  • No need for '=' to print
  • Easy help with: ? funcname
  • Self help: ?
  • Shell commands with: $ cmd (example: $ ls)

Next steps

In addition to this manual, there are various other resources that may help new users get started with torch, all summarized in this Cheatsheet

The cheatsheet provides links to tutorials, demos, package summaries and a lot of useful information.

If you have a question, please come join the Torch users mailing list