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Getting Started

Ankan Banerjee edited this page Mar 15, 2019 · 26 revisions


Lc0 has three main parts:

NAME FILE Function Needed for Contributing Needed for Playing
Engine lc0.exe Does the tree search and calls the NN to get evaluations YES YES
Network (NN) Varies e.g. weights_run2_32930.pb.gz Stores the Neural Net's evaluation function NO YES
Client client.exe Gets the latest network from the server, generates self-play games, and uploads the training data to the server YES NO
  • To help the project by donating GPU time, you need all three of these, and you should run client.exe. The client will automatically run lc0.exe, download the network for training, and ask the server what to do. If this doesn't work right away try debugging by running lc0.exe (see Debug section below).

  • To play or analyze games with Lc0, you don't need client.exe, but you do need the engine lc0.exe and a network file. The best way to do this is using a chess GUI. See the guide in our blog.



Can be downloaded from

  • Windows --> client.exe
  • Linux --> client_linux
  • Mac --> client_mac
  • Note: recent versions of engine package include client.exe



Download a network from

  • The name will be some long hash string, for example: b82f0b34b96c8f38f68ee97703b4149ab976122ca9bed6120f9dea88d733d266
  • Rename to "weights" (for convenience).
  • Place in the same directory with the lc0 application. On a Mac this is /Users/[username]/lc0/build/release/.
  • The file will be found automatically after opening lc0 in the command line.

Note that the latest network is not always the strongest. To find a strong network ID, check the "Test30" tab in this Google Doc.

Get started analyzing positions

  • Open the lc0 application.
  • Enter the command "go nodes 100" in the terminal.
  • lc0 will begin a configuration process, which will only happen once. Then it will analyze the starting position for 100 nodes.
  • To increase the quality of analysis, use more nodes.
  • To analyse a position, type for example, "position startpos moves e2e4 e7e5", where the moves lead to the desired position. Then use "go nodes [number]" again.


  • For easier debug, verify install by running from command line (cmd.exe)
    • cd to directory with lc0.exe.
    • run lc0.exe --logfile=log.txt
      • Most recent weights file in that directory will be used automatically.
      • Add --weights=c:\path\to\weights_476.txt.gz to specify manually.
    • Example expected output:
|   _ | |
|_ |_ |_| built Jul  8 2018
  • Type go nodes 100
  • Example expected output:
go nodes 100
Found network file: C:\Users\aolsen\Desktop\Engines\lc0-win-20180708-cuda92-cudnn714/weights_476.txt.gz
Creating backend [cudnn]...
info depth 2 seldepth 2 time 28 nodes 2 score cp 21 hashfull 0 nps 71 pv c2c4 g8f6
info depth 2 seldepth 3 time 39 nodes 4 score cp 19 hashfull 0 nps 102 pv c2c4 e7e5 g2g3
info depth 2 seldepth 4 time 56 nodes 15 score cp 20 hashfull 0 nps 267 pv c2c4 c7c5 g1f3 g8f6
info depth 2 seldepth 5 time 73 nodes 34 score cp 20 hashfull 0 nps 465 pv c2c4 c7c5 g1f3 g8f6 b1c3
info depth 2 seldepth 6 time 92 nodes 73 score cp 20 hashfull 0 nps 793 pv c2c4 c7c5 g1f3 g8f6 b1c3 e7e6
info depth 2 seldepth 7 time 111 nodes 121 score cp 20 hashfull 0 nps 1090 pv c2c4 c7c5 g1f3 g8f6 b1c3 b8c6 d2d4
info depth 2 seldepth 7 time 114 nodes 121 score cp 20 hashfull 0 nps 1061 pv c2c4 c7c5 g1f3 g8f6 b1c3 b8c6 d2d4
bestmove c2c4
  • type quit to exit the program.
  • Common problems
    • lc0.exe exits without printing anything
      • Double check you have cublas64_100.dll, cudart64_100.dll, and cudnn64_7.dll in the same directory as lc0.exe
    • CUDA driver version is insufficient for CUDA runtime version
      • You need 411.31 or newer. Download latest from nvidia's website.
    • error Network weights file not found
      • Download the latest weights from and place in the same directory as lc0.exe.
      • OR: point to the weights using --weights=c:\path\to\weights_run2_32282.pb.gz
    • If there are other problems, please upload log.txt to the discord chat #help channel.


Join the discord for quick help, it is usually very active.

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