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optional sizehint for building matrix #199

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merged 3 commits into from
Mar 30, 2023
Merged

optional sizehint for building matrix #199

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1ff8795
init
christofbradly Mar 30, 2023
84c331b
Update src/Hamiltonians/abstract.jl
christofbradly Mar 30, 2023
a2d537e
BSR doc
christofbradly Mar 30, 2023
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init
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@christofbradly
christofbradly committed Mar 30, 2023
commit 1ff8795f5e3c9b0c47d2553d0f7fc3ee1de53f30
10 changes: 7 additions & 3 deletions src/Hamiltonians/abstract.jl
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Expand Up @@ -145,7 +145,7 @@ momentum

"""
sm, basis = build_sparse_matrix_from_LO(
ham, address=starting_address(ham); cutoff, filter=nothing, nnzs, sort=false, kwargs...
ham, address=starting_address(ham); cutoff, filter=nothing, nnzs, col_hint, sort=false, kwargs...
)

Create a sparse matrix `sm` of all reachable matrix elements of a linear operator `ham`
Expand All @@ -155,6 +155,10 @@ configurations.
Providing the number `nnzs` of expected calculated matrix elements may improve performance.
The default estimates for `nnzs` is `dimension(ham)`.

Setting a custom `col_hint` may improve performance for cases where `num_offdiagonals` is
not a good estimate of the actual number of nonzero offdiagonal elements in each column.
Defaults to `num_offdiagonals(ham, address)`.

Providing an energy cutoff will skip the columns and rows with diagonal elements greater
than `cutoff`. Alternatively, an arbitrary `filter` function can be used instead. These are
not enabled by default.
Expand All @@ -169,7 +173,7 @@ function build_sparse_matrix_from_LO(
ham, address=starting_address(ham);
cutoff=nothing,
filter=isnothing(cutoff) ? nothing : (a -> diagonal_element(ham, a) ≤ cutoff),
nnzs=dimension(ham),
nnzs=dimension(ham), col_hint=num_offdiagonals(ham, address),
sort=false, kwargs...,
)
if !isnothing(filter) && !filter(address)
Expand All @@ -182,7 +186,7 @@ function build_sparse_matrix_from_LO(
adds = [address] # Queue of addresses. Also returned as the basis.
dict = Dict(address => 1) # Mapping from addresses to indices
col = Dict{Int,T}() # Temporary column storage
sizehint!(col, num_offdiagonals(ham, address))
sizehint!(col, col_hint)

is = Int[] # row indices
js = Int[] # column indice
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