Stockfish 4

Stockfish 4 has been released. You can download at or browse the sources at

Diffs from last version is: 43 files changed, 1534 insertions(+), 1703 deletions(-)

So 169 lines of code less but should be quite stronger than version 3. For interested people here is the breakdown of lines count.

Language files blank comment code

C++ 20 2110 1619 5772 C/C++ Header 21 636 570 1558 SUM: 41 2746 2189 7330

This is the first release where we have took full advantage of the power of our distributed and public testing framework. At one point we reached 41 active machines connected for a total of 136 cores and a compound testing power of 190M nps (nodes per second). This is even more noteworthy considering that Gary’s 24 core monster was offline at that moment.

But is the the ‘public’ part of our development model that is the real advantage we have and without which the improvement above SF 3 would have not been possible, no matter how hardware we throw at it.

So here is the list of developers that contributed to this release:

  • Dan Schmidt
  • Dariusz Orzechowski
  • Eelco de Groot
  • Gary Linscott
  • jhellis3
  • Joona Kiiski
  • jundery
  • Leonid Pechenik
  • Marco Costalba
  • Reuven Peleg
  • Ryan Schmitt
  • Ryan Takker
  • Tom Vijlbrief
  • Uri Blass

A special thank to Daylen Yang, our precious webmaster and builder of the Mac binaries, to Peter Österlund for the Android version and to from which I have, shameless, took the Windows binaries.

For the first time since Stockfish was borne, Jim Ablett didn’t compile the official builds and this is a big miss for us and for me in particular. I’d like to publicly thank him again for the help and support during all these years.

Finally a note for the user. In this version there is no more automatic detection of CPU count, so at startup Stockfish always defaults to 1 thread. In case you want to use more than one CPU you have to manually set the “Threads” UCI option accordingly.

Have Fun
SF Team

UPDATE: Just to add another technical detail, that I forgot to mention in the announcement, for the people compiling themselves please verify build is ok running:

./stockfish bench

Searched node count must be: 4132374