University of Cologne

Faculty of Mathematics and Natural Sciences
Computer Science Department - COPhy Junior Research Group

Spin Glass Server
(This service is provided by COPhy and M. Jünger's group.)

This page offers a service to compute exact ground states of Ising spin glasses and partition functions of Potts glasses with many states.
Instances can be uploaded using this web-interface or our command-line client (for Unix/Linux based OS). The results are returned by email.
We recommend to use the command-line client for the submission of many instances.

The following geometries are supported:
• Ising spin glass on a:
• two-dimensional planar quadratic lattice (free boundary in at least one direction)
• two-dimensional quadratic lattice on a torus (periodic boundaries in both directions)
• three-dimensional lattice (periodic boundaries in all directions)
• complete graph (Sherrington-Kirkpatrick (SK) spin-glass model). For the SK model, we use an algorithm provided to us by our colleagues G. Rinaldi, F. Rendl and A. Wiegele.

(each instance has to be a text file; files can be bundled into an archive; supported archive-formats are tar, tar.gz and zip)
 file name type Ising spin glass Potts infinite email address

The input format is as follows:

``` name: the name of the instance spin_i1   spin_j1   coupling between i1 and j1 spin_i2   spin_j2   coupling between i2 and j2 ... ```

If the instance should be named like the filename, simply skip the line `name: ...` in the file.
Lattices with uniformly distributed ±J couplings need to be scaled to ±1 couplings.

See an example of the input format together with the corresponding results from the server here.
For lattice models, spins are numbered sequentially layer by layer starting with index 1.
For example, a two-dimensional 3x3 spin glass is numbered as follows:

|       |       |
-(1)---(2)---(3)--
|       |       |
-(4)---(5)---(6)--
|       |       |
-(7)---(8)---(9)--
|       |       |

For the non-lattice models such as the Sherrington-Kirkpatrick (SK) model, the order of the spins is arbitrary.