Compiler-generated variable names
| Gate | _cases - Used to represent an integer or boolean gate selector via a 1-of-N encoding. |
| Depth cloning | _depthN - Created when a jagged array is used at different indexing depths. |
| Replication | _rep[] - When a variable is used inside a (range) loop, it is replicated for each iteration. |
| Variable | _use & _marginal - The Variable factor is introduced for each variable that needs to be inferred. The output edge of this factor is suffixed by _use. For instance, if we want to infer the variable mean, the input edge to the introduced factor will be called mean, and the output edge will be called mean_use. The marginal distribution is stored in a variable suffixed by _marginal. |
| Channel 2 | _uses[] - When a variable is used multiple times in the model, its uses are disambiguated by adding the _uses[] suffix (one element of this array for each use of the variable). This achieves a 1:1 mapping from variables to edges. An exception to this rule may be made when the same variable is used within gates. |
| Message | _F & _B - Each edge becomes a message. The forward messages are suffixed by _F, and the backward messages are suffixed by _B. _toDef & _marginal - When the product of the children of replicate has to be stored in a buffer, a variable suffixed by _toDef is used. This allows to optimize the computation of the forward message by dividing the value in the _toDef variable by the backward message. Similarly, if the marginal needs to be buffered, it is stored in a variable suffixed by _marginal. Note that this variable is different from the one introduced by the Variable transform. It differs in that the one here will be called *_F/B_marginal, while the one from Variable will be called *_marginal_F/B. However, they should hold exactly the same value (once both are updated). |
| Hoisting | _hoist - When the value of a variable is computed multiple times inside a loop, but the computations performed are the same for each iteration, then this computation is taken outside the loop. The temporary variable created is called _hoist. If multiple such optimizations need to be made, then the new variables are called _hoist1, …, _hoistN. |
| Dependency Analysis | Sometimes adds special comment statements (called dummy statements in the compiler). These are used to express complex dependencies. For example: if(priorType) { x_F = … } if(!priorType) { x_F = .. } // x_F is now defined in all cases <– This is the dummy statement g(x_F) |