Add project convenience for symmetry-restricted arrays and TensorMap support#203
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…support Adds `project`, an owned convenience over the existing `project_map` hook for building a symmetry-restricted array from a dense one. The three-argument form takes an explicit codomain/domain split and the two-argument form takes a flat list of axes (an empty domain), both forwarding to `project_map`. `checked_project` is the verified counterpart of `checked_project_map`. This mirrors the `zeros`/`zeros_map` pairing, where the unsuffixed name is the convenience that also accepts the codomain/domain split. Also adds the `TensorMap` path in the TensorKit extension so `project` can build a `TensorMap` from a dense array: `similar_map` allocates a same-device buffer whose block storage type follows the dense prototype, `projectto!` fills the symmetry-allowed blocks through `project_symmetric!` and discards the rest, and `checked_projectto!` verifies the projection by norm, since a dense array and a `TensorMap` are not comparable elementwise and projection onto the symmetric blocks preserves the norm exactly when nothing is discarded.
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The two `similar_map` methods for a dense prototype with space axes had identical bodies and existed only to pin the elementary space type `S` from whichever of codomain/domain is non-empty. Factor the body into a `similar_tensormap` helper that takes `S` explicitly, matching the `_map_homspace` helper and the two-entries-per-constructor pattern used for the map constructors.
Densify the `TensorMap` destination with `convert(Array, ...)` and reuse the dense path's `isapprox(src, dest)` check in `checked_projectto!` instead of the norm-based shortcut, so the check keeps one `InexactError`/`kwargs` contract across backends rather than diverging toward TensorKit's residual-norm `tol`/`ArgumentError` check.
mtfishman
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## Summary Adds methods extending `TensorAlgebra.project` and `TensorAlgebra.checked_project` (added in ITensor/TensorAlgebra.jl#203) that build a named tensor from a dense array and the indices to attach. The three-argument form takes a codomain/domain split (an operator), and the two-argument form takes a flat list of indices (a state, i.e. an empty domain). The index axes select the backend, so the same call builds an `Array` on dense indices, a block-sparse array on graded indices, and a `TensorMap` on TensorKit spaces. The named entry strips to the unnamed array plus axes, lowers to `TensorAlgebra.project`, and reattaches the names. This is the named-index projection primitive for building symmetric operators and states from a dense basis matrix: `project(Sz, (i',), (i,))` for an operator, `project(v, (i,))` for a state.
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Summary
Adds
project, an owned convenience over the existingproject_maphook for building a symmetry-restricted array from a dense one. The three-argument form takes an explicit codomain/domain split and the two-argument form takes a flat list of axes (an empty domain), both forwarding toproject_map, andchecked_projectis the verified counterpart ofchecked_project_map. This mirrors thezeros/zeros_mappairing, where the unsuffixed name is the convenience that also accepts the codomain/domain split.Also adds the
TensorMappath in the TensorKit extension soprojectcan build aTensorMapfrom a dense array:similar_mapallocates a same-device buffer whose block storage type follows the dense prototype,projectto!fills the symmetry-allowed blocks throughproject_symmetric!and discards the rest, andchecked_projectto!verifies the projection by densifying the result and reusing the dense path's elementwiseisapprox(src, dest)check, so it keeps oneInexactError/kwargscontract across backends.The named-index
projectforAbstractITensoris added in ITensor/ITensorBase.jl#208.