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add iterative bitflip decoder (#255)
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@Krastanov
Krastanov committed Apr 9, 2024
1 parent 9a36302 commit 4a007f9
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4 changes: 4 additions & 0 deletions CHANGELOG.md
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Expand Up @@ -5,6 +5,10 @@

# News

## v0.9.3 - 2024-04-08

- The ECC module now has access to an iterative bitflip decoder thanks to `LDPCDecoders.jl`.

## v0.9.2 - 2024-04-02

- Provide more configuration options in the `PyBeliefProp` decoders.
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2 changes: 1 addition & 1 deletion Project.toml
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@@ -1,7 +1,7 @@
name = "QuantumClifford"
uuid = "0525e862-1e90-11e9-3e4d-1b39d7109de1"
authors = ["Stefan Krastanov <stefan@krastanov.org> and QuantumSavory community members"]
version = "0.9.2"
version = "0.9.3"

[deps]
Combinatorics = "861a8166-3701-5b0c-9a16-15d98fcdc6aa"
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71 changes: 51 additions & 20 deletions ext/QuantumCliffordLDPCDecodersExt/QuantumCliffordLDPCDecodersExt.jl
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Expand Up @@ -6,56 +6,87 @@ using QuantumClifford
using QuantumClifford.ECC
import QuantumClifford.ECC: AbstractSyndromeDecoder, decode, parity_checks

struct BeliefPropDecoder <: AbstractSyndromeDecoder
"""Stabilizer tableau defining the code"""
struct BeliefPropDecoder <: AbstractSyndromeDecoder # TODO all these decoders have the same fields, maybe we can factor out a common type
H
"""Faults matrix corresponding to the code"""
faults_matrix
"""The number of qubits in the code"""
n
"""The depth of the code"""
s
"""The number of encoded qubits"""
k
"""Number of X checks"""
cx
"""Number of X checks"""
cz
"""The classical BP decoder for Hx"""
bpdecoderx
"""The classical BP decoder for Hz"""
bpdecoderz
end

function BeliefPropDecoder(c, p_init=0, max_iters=10)
struct BitFlipDecoder <: AbstractSyndromeDecoder # TODO all these decoders have the same fields, maybe we can factor out a common type
H
faults_matrix
n
s
k
cx
cz
bfdecoderx
bfdecoderz
end

function BeliefPropDecoder(c; errorrate=nothing, maxiter=nothing)
Hx = parity_checks_x(c)
Hz = parity_checks_z(c)
H = parity_checks(c)
s, n = size(H)
_, _, r = canonicalize!(Base.copy(H), ranks=true)
k = n - r
cx = size(Hx, 1)
cz = size(Hx, 1)
cz = size(Hz, 1)
fm = faults_matrix(H)

bpx = LDPCDecoders.BeliefPropagationDecoder(Hx, p_init, max_iters)
bpz = LDPCDecoders.BeliefPropagationDecoder(Hz, p_init, max_iters)
isnothing(errorrate) || 0≤errorrate≤1 || error(lazy"BeliefPropDecoder got an invalid error rate argument. `errorrate` must be in the range [0, 1].")
errorrate = isnothing(errorrate) ? 0.0 : errorrate
maxiter = isnothing(maxiter) ? n : maxiter
bpx = LDPCDecoders.BeliefPropagationDecoder(Hx, errorrate, maxiter)
bpz = LDPCDecoders.BeliefPropagationDecoder(Hz, errorrate, maxiter)

return BeliefPropDecoder(H, fm, n, s, k, cx, cz, bpx, bpz)
end

function BitFlipDecoder(c; errorrate=nothing, maxiter=nothing)
Hx = parity_checks_x(c)
Hz = parity_checks_z(c)
H = parity_checks(c)
s, n = size(H)
_, _, r = canonicalize!(Base.copy(H), ranks=true)
k = n - r
cx = size(Hx, 1)
cz = size(Hz, 1)
fm = faults_matrix(H)

isnothing(errorrate) || 0≤errorrate≤1 || error(lazy"BitFlipDecoder got an invalid error rate argument. `errorrate` must be in the range [0, 1].")
errorrate = isnothing(errorrate) ? 0.0 : errorrate
maxiter = isnothing(maxiter) ? n : maxiter
bfx = LDPCDecoders.BitFlipDecoder(Hx, errorrate, maxiter)
bfz = LDPCDecoders.BitFlipDecoder(Hz, errorrate, maxiter)

return BitFlipDecoder(H, fm, n, s, k, cx, cz, bfx, bfz)
end

parity_checks(d::BeliefPropDecoder) = d.H
parity_checks(d::BitFlipDecoder) = d.H

function decode(d::BeliefPropDecoder, syndrome_sample)
row_x = syndrome_sample[1:d.cx]
row_z = syndrome_sample[d.cx+1:d.cx+d.cz]
guess_z, success = LDPCDecoders.decode!(d.bpdecoderx, row_x)
guess_x, success = LDPCDecoders.decode!(d.bpdecoderz, row_z)
return vcat(guess_x, guess_z)
end

guess_x = falses(d.n)
guess_z = falses(d.n)

success = LDPCDecoders.decode!(d.bpx, row_x, guess_x)
success = LDPCDecoders.decode!(d.bpz, row_z, guess_z)
return vcat(guess_z, guess_x)
function decode(d::BitFlipDecoder, syndrome_sample)
row_x = syndrome_sample[1:d.cx]
row_z = syndrome_sample[d.cx+1:d.cx+d.cz]
guess_z, success = LDPCDecoders.decode!(d.bfdecoderx, row_x)
guess_x, success = LDPCDecoders.decode!(d.bfdecoderz, row_z)
return vcat(guess_x, guess_z)
end

end
17 changes: 11 additions & 6 deletions ext/QuantumCliffordPyQDecodersExt/QuantumCliffordPyQDecodersExt.jl
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Expand Up @@ -8,7 +8,7 @@ import QuantumClifford.ECC: AbstractSyndromeDecoder, decode, batchdecode, parity

abstract type PyBP <: AbstractSyndromeDecoder end

struct PyBeliefPropDecoder <: PyBP
struct PyBeliefPropDecoder <: PyBP # TODO all these decoders have the same fields, maybe we can factor out a common type
code
H
Hx
Expand All @@ -20,7 +20,7 @@ struct PyBeliefPropDecoder <: PyBP
pyz
end

struct PyBeliefPropOSDecoder <: PyBP
struct PyBeliefPropOSDecoder <: PyBP # TODO all these decoders have the same fields, maybe we can factor out a common type
code
H
Hx
Expand All @@ -47,7 +47,7 @@ function PyBeliefPropDecoder(c; maxiter=nothing, bpmethod=nothing, errorrate=not
return PyBeliefPropDecoder(c, H, Hx, Hz, size(Hx, 1), size(Hz, 1), fm, pyx, pyz)
end

function PyBeliefPropOSDecoder(c; maxiter=nothing, bpmethod=nothing, errorrate=nothing)
function PyBeliefPropOSDecoder(c; maxiter=nothing, bpmethod=nothing, errorrate=nothing, osdmethod=nothing, osdorder=0)
Hx = parity_checks_x(c) |> collect # TODO should be sparse
Hz = parity_checks_z(c) |> collect # TODO should be sparse
H = parity_checks(c)
Expand All @@ -57,8 +57,12 @@ function PyBeliefPropOSDecoder(c; maxiter=nothing, bpmethod=nothing, errorrate=n
bp_method = get(Dict(:productsum => 0, :minsum => 1, :minsumlog => 2), bpmethod, 0)
isnothing(errorrate) || 0≤errorrate≤1 || error(lazy"PyBeliefPropDecoder got an invalid error rate argument. `errorrate` must be in the range [0, 1].")
error_rate = isnothing(errorrate) ? PythonCall.Py(nothing) : errorrate
pyx = ldpc.bposd_decoder(np.array(Hx); max_iter, bp_method, error_rate) # TODO should be sparse
pyz = ldpc.bposd_decoder(np.array(Hz); max_iter, bp_method, error_rate) # TODO should be sparse
isnothing(osdmethod) || osdmethod ∈ (:zeroorder, :exhaustive, :combinationsweep) || error(lazy"PyBeliefPropOSDecoder got an unknown OSD method argument. `osdmethod` must be one of :zeroorder, :exhaustive, :combinationsweep.")
osd_method = get(Dict(:zeroorder => "osd0", :exhaustive => "osde", :combinationsweep => "osdcs"), osdmethod, 0)
0≤osdorder || error(lazy"PyBeliefPropOSDecoder got an invalid OSD order argument. `osdorder` must be ≥0.")
osd_order = osdorder
pyx = ldpc.bposd_decoder(np.array(Hx); max_iter, bp_method, error_rate, osd_method, osd_order) # TODO should be sparse
pyz = ldpc.bposd_decoder(np.array(Hz); max_iter, bp_method, error_rate, osd_method, osd_order) # TODO should be sparse
return PyBeliefPropOSDecoder(c, H, Hx, Hz, size(Hx, 1), size(Hz, 1), fm, pyx, pyz)
end

Expand All @@ -67,12 +71,13 @@ parity_checks(d::PyBP) = d.H
function decode(d::PyBP, syndrome_sample)
row_x = syndrome_sample[1:d.nx] # TODO These copies and indirections might be costly!
row_z = syndrome_sample[d.nx+1:end]
@show (size(row_x), size(row_z))
guess_z_errors = PythonCall.PyArray(d.pyx.decode(np.array(row_x)))
guess_x_errors = PythonCall.PyArray(d.pyz.decode(np.array(row_z)))
vcat(guess_x_errors, guess_z_errors)
end

struct PyMatchingDecoder <: AbstractSyndromeDecoder
struct PyMatchingDecoder <: AbstractSyndromeDecoder # TODO all these decoders have the same fields, maybe we can factor out a common type
code
H
Hx
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2 changes: 1 addition & 1 deletion src/ecc/ECC.jl
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Expand Up @@ -23,7 +23,7 @@ export parity_checks, parity_checks_x, parity_checks_z, iscss,
evaluate_decoder,
CommutationCheckECCSetup, NaiveSyndromeECCSetup, ShorSyndromeECCSetup,
TableDecoder,
BeliefPropDecoder,
BeliefPropDecoder, BitFlipDecoder,
PyBeliefPropDecoder, PyBeliefPropOSDecoder, PyMatchingDecoder

"""Parity check tableau of a code.
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10 changes: 10 additions & 0 deletions src/ecc/decoder_pipeline.jl
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Expand Up @@ -241,6 +241,16 @@ function BeliefPropDecoder(args...; kwargs...)
return ext.BeliefPropDecoder(args...; kwargs...)
end

"""An Iterative Bitflip decoder built around tools from `LDPCDecoders.jl`."""
function BitFlipDecoder(args...; kwargs...)
ext = Base.get_extension(QuantumClifford, :QuantumCliffordLDPCDecodersExt)
if isnothing(ext)
throw("The `BitFlipDecoder` depends on the package `LDPCDecoders` but you have not installed or imported `LDPCDecoders` yet. Immediately after you import `LDPCDecoders`, the `BitFlipDecoder` will be available.")
end
return ext.BitFlipDecoder(args...; kwargs...)
end


"""A Belief Propagation decoder built around tools from the python package `ldpc` available from the julia package `PyQDecoders.jl`."""
function PyBeliefPropDecoder(args...; kwargs...)
ext = Base.get_extension(QuantumClifford, :QuantumCliffordPyQDecodersExt)
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Registration pull request created: JuliaRegistries/General/104525

Tip: Release Notes

Did you know you can add release notes too? Just add markdown formatted text underneath the comment after the text
"Release notes:" and it will be added to the registry PR, and if TagBot is installed it will also be added to the
release that TagBot creates. i.e.

@JuliaRegistrator register

Release notes:

## Breaking changes

- blah

To add them here just re-invoke and the PR will be updated.

Tagging

After the above pull request is merged, it is recommended that a tag is created on this repository for the registered package version.

This will be done automatically if the Julia TagBot GitHub Action is installed, or can be done manually through the github interface, or via:

git tag -a v0.9.3 -m "<description of version>" 4a007f913a92e9d8bc934917498209c17fbd4f3f
git push origin v0.9.3

Also, note the warning: Version 0.9.3 skips over 0.9.2
This can be safely ignored. However, if you want to fix this you can do so. Call register() again after making the fix. This will update the Pull request.

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