Programmer's Guide: How To Create Network Types

The file type.h contains the bit-masks used to encode types for networks, groups, units, link blocks, projection patterns, example set selection modes, noise types, algorithms, and a number of other things. Currently the only non-standard network types are CONTINUOUS and BOLTZMANN. You may want to create a new network type if you want to run a network that uses substantially different training functions at the network-level, not just the group level.

The first thing you need to do is to choose a bitmask for your type. This should be put in your own personal version of the type.h file. Be sure to use comments to mark your addition so you can recreate it when type.h is updated. When adding a new type, you will need to add a #define like those in util.h and choose an unused bit. The shift (the number following << can range from 0 to 31). Just be sure you don't use a bit that has already been taken by one of the SHARED TYPES or NETWORK TYPES.

For example, we might add:

    /* DOUG... */
    #define COOL_NET    ((mask) 1 << 9)
    /* ...DOUG */

Now you will probably want to write some functions to train or test your network on an example or a tick. Those should be placed in extension.c. Let's pretend we wrote the functions coolNetTrainExample(), coolNetTestExample(), and coolNetUpdate().

Next, you need to write a type initializer. This will be used to set the network's function pointers to the functions you just wrote when the network is created. Put it in extension.c as well. Your initializer might look like this:

    static flag initCoolNet(Network N) {
      N->netTrainExample  = coolNetTrainExample;
      N->netTestExample   = coolNetTestExample;
      N->netRunExample    = coolNetTrainExample;
      N->netTrainTick     = coolUpdate;
      N->netTestTick      = coolUpdate;
      N->netRunTick       = coolUpdate;
      return TCL_OK;
    }

All of the functions you don't set here will be set by the initStandardNet() procedure in act.c.

Finally, you need to register your type. This is done by placing a call to registerNetType() in userInit() in extension.c. For example:

    registerNetType("COOL_NET", COOL_NET, initCoolNet);

The first argument is the name users will call this type when issuing shell commands. The second is the code that you just defined in type.c and the third is the type initialization function. Now you should be able to issue the shell command:

    addNet foo COOL_NET

and the network will use the example- and tick-processing functions you wrote.

If you need to do other things to initialize your network, you could always define your own command which could do anything you like.