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| # Interfaces | ||
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| Julia doesn't have a formal definition of interface built into the language. Instead it relies on [duck typing](https://wikipedia.org/wiki/Duck_typing). | ||
| Any declaration of a formal interface is then the documentation written for it. | ||
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| ## [TensorNetwork](@id man-interface-tensornetwork) | ||
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| A [`TensorNetwork` (interface)](@ref man-interface-tensornetwork) is a collection of [`Tensor`](@ref)s forming a graph structure. | ||
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| | Required method | Brief description | | ||
| | :----------------------------------- | :---------------------------------------------------- | | ||
| | [`tensors(tn)`](@ref tensors) | Returns the list of [`Tensor`](@ref)s present in `tn` | | ||
| | `inds_set_all` | | | ||
| | `inds_set_open` | | | ||
| | `inds_set_inner` | | | ||
| | `inds_set_hyper` | | | ||
| | `replace!(tn, index => new_index)` | | | ||
| | `replace!(tn, tensor => new_tensor)` | | | ||
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| !!! todo | ||
| - Are `contract` and `contract!` required methods for the interface? | ||
| - Is conversion to `TensorNetwork` a required method method for the interface? | ||
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| The `inds_set_all`, `inds_set_inner`, `inds_set_open` and `inds_set_hyper` are the underlying functions used by `inds(tn; set)`, so they are required for it to work. | ||
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| !!! todo | ||
| We are looking for a better way to add value-dispatch to [`inds`](@ref) (specifically, the `inds(tn; set)` method) without incurring in huge dynamic dispatch overhead (like the `Val`-dispatch method). | ||
| We might be interested in studying the internal mechanism used in [ValSplit.jl](https://github.com/ztangent/ValSplit.jl). | ||
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| The following methods are optional but you might be interested on implementing them for performance purposes. | ||
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| | Method | Default definition | Brief description | | ||
| | :--------------- | :----------------------------------------------------------- | :---------------------------------------------------------------- | | ||
| | `size(tn)` | Get index sizes from `tensors(tn)` | Returns a `Dict` that maps indices to their sizes | | ||
| | `size(tn, i)` | Get first matching tensor from `tensors(tn)` and query to it | Returns the size of the given index `i` | | ||
| | `arrays` | `parent.(tensors(tn))` | Returns the arrays wrapped by the [`Tensor`](@ref)s in `tn` | | ||
| | `ninds` | `length(inds(tn))` | Returns the number of indices in `tn` | | ||
| | `ntensors` | `length(tensors(tn))` | Returns the number of tensors contained in `tn` | | ||
| | `in(index, tn)` | `in(index, inds(tn))` | Returns `true` if `index` is a existing index in `tn` | | ||
| | `in(tensor, tn)` | `in(tensor, tensors(tn))` | Returns `true` if `tensor` is a existing [`Tensor`](@ref) in `tn` | | ||
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| ## [Pluggable](@id man-interface-pluggable) | ||
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| A [`Pluggable`](@ref man-interface-pluggable) is a [`TensorNetwork`](@ref man-interface-tensornetwork) together with a mapping between [`Site`](@ref)s and open indices. | ||
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| | Required method | Brief description | | ||
| | :------------------------ | :-------------------------------------------------------------------------------------- | | ||
| | [`sites(tn)`](@ref sites) | Returns the list of [`Site`](@ref)s present in `tn` | | ||
| | `ind_at(tn, at)` | Return the index linked to the `at` `Symbol` | | ||
| | `site_at(tn, at)` | Return the [`Site`](@ref) linked to the index `at` | | ||
| | `inds_set_physical(tn)` | Return the indices linked to [`Site`](@ref); i.e. the ones behaving as physical indices | | ||
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| | Method | Default definition | Brief description | | ||
| | :---------------------- | :----------------------------- | :---------------------------------------------------- | | ||
| | `nsites(tn; kwargs...)` | `length(sites(tn; kwargs...))` | Returns the number of [`Site`](@ref)s present in `tn` | | ||
| | `in(site, tn)` | `in(site, sites(tn))` | Returns `true` if `site` exists in `tn` | | ||
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| !!! danger | ||
| Do not just forward calls to `replace!(tn, index => new_index)` because it would break the mapping between [`Site`](@ref)s and indices when a mapped index is replaced. | ||
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| ## [Ansatz](@id man-interface-ansatz) | ||
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| A [`Ansatz`](@ref man-interface-ansatz) is a [`TensorNetwork`](@ref man-interface-tensornetwork) together with a mapping between [`Lane`](@ref)s and [`Tensor`](@ref)s. | ||
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| | Required method | Brief description | | ||
| | :------------------------ | :--------------------------------------------------------------------------------------------------------- | | ||
| | [`lanes(tn)`](@ref lanes) | Returns the list of [`Lane`](@ref)s present in `tn` | | ||
| | `tensor_at(tn, at)` | Returns the [`Tensor`](@ref) linked to the `at` [`Lane`](@ref). Dispatched through `tensors(tn; at::Lane)` | | ||
| | `lattice(tn)` | Returns the [`Lattice`](@ref) associated to `tn` | | ||
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| | Method | Default definition | Brief description | | ||
| | :------------- | :-------------------- | :---------------------------------------------------- | | ||
| | `nlanes(tn)` | `length(lanes(tn))` | Returns the number of [`Lane`](@ref)s present in `tn` | | ||
| | `in(lane, tn)` | `in(lane, lanes(tn))` | Returns `true` if `lane` exists in `tn` | | ||
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| !!! danger | ||
| Do not just forward calls to `replace!(tn, index => new_index)` nor `replace!(tn, tensor => new_tensor)` because it would break the mapping between [`Lane`](@ref)s and [`Tensor`](@ref)s when a mapped [`Tensor`] is replaced. |