From 7f33ba456bd273866079d2c375d69100124a6665 Mon Sep 17 00:00:00 2001
From: mtfishman <mfishman@flatironinstitute.org>
Date: Mon, 9 Mar 2026 14:17:01 -0400
Subject: [PATCH 01/15] Fix slicing of GradedArrays

---
 src/abstractblocksparsearray/arraylayouts.jl | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/abstractblocksparsearray/arraylayouts.jl b/src/abstractblocksparsearray/arraylayouts.jl
index 5b6e80a7..edffeb29 100644
--- a/src/abstractblocksparsearray/arraylayouts.jl
+++ b/src/abstractblocksparsearray/arraylayouts.jl
@@ -62,7 +62,10 @@ function ArrayLayouts.sub_materialize(layout::BlockLayout{<:SparseLayout}, a, ax
     # TODO: Use `similar`?
     blocktype_a = blocktype(parent(a))
     a_dest = BlockSparseArray{eltype(a), length(axes), blocktype_a}(undef, axes)
-    a_dest .= a
+    for I in SparseArraysBase.eachstoredindex(blocks(a))
+        b = Block(Tuple(I))
+        a_dest[b] = blocks(a)[Tuple(I)...]
+    end
     return a_dest
 end
 

From 0082d2557db5d0de92c2887d416a7ebf76038504 Mon Sep 17 00:00:00 2001
From: mtfishman <mfishman@flatironinstitute.org>
Date: Mon, 9 Mar 2026 14:48:52 -0400
Subject: [PATCH 02/15] Adustments to slicing

---
 src/abstractblocksparsearray/arraylayouts.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/abstractblocksparsearray/arraylayouts.jl b/src/abstractblocksparsearray/arraylayouts.jl
index edffeb29..b8329c19 100644
--- a/src/abstractblocksparsearray/arraylayouts.jl
+++ b/src/abstractblocksparsearray/arraylayouts.jl
@@ -64,7 +64,7 @@ function ArrayLayouts.sub_materialize(layout::BlockLayout{<:SparseLayout}, a, ax
     a_dest = BlockSparseArray{eltype(a), length(axes), blocktype_a}(undef, axes)
     for I in SparseArraysBase.eachstoredindex(blocks(a))
         b = Block(Tuple(I))
-        a_dest[b] = blocks(a)[Tuple(I)...]
+        a_dest[b] = copy(blocks(a)[Tuple(I)...])
     end
     return a_dest
 end

From 006cae4cd6f1d93bc9f2049b596f8e8b9a2f9123 Mon Sep 17 00:00:00 2001
From: mtfishman <mfishman@flatironinstitute.org>
Date: Mon, 9 Mar 2026 15:37:08 -0400
Subject: [PATCH 03/15] More progress

---
 .../BlockSparseArraysTensorAlgebraExt.jl      | 23 +++++++++---------
 src/abstractblocksparsearray/arraylayouts.jl  | 24 ++++++++++++-------
 2 files changed, 27 insertions(+), 20 deletions(-)

diff --git a/ext/BlockSparseArraysTensorAlgebraExt/BlockSparseArraysTensorAlgebraExt.jl b/ext/BlockSparseArraysTensorAlgebraExt/BlockSparseArraysTensorAlgebraExt.jl
index 25384e05..917119df 100644
--- a/ext/BlockSparseArraysTensorAlgebraExt/BlockSparseArraysTensorAlgebraExt.jl
+++ b/ext/BlockSparseArraysTensorAlgebraExt/BlockSparseArraysTensorAlgebraExt.jl
@@ -41,17 +41,11 @@ function TensorAlgebra.matricize(
     key(I) = Block(Tuple(I))
     value(I) = matricize(reshaped_blocks_a[I], length_codomain)
     Is = eachstoredindex(reshaped_blocks_a)
-    bs = if isempty(Is)
-        # Catch empty case and make sure the type is constrained properly.
-        # This seems to only be necessary in Julia versions below v1.11,
-        # try removing it when we drop support for those versions.
-        keytype = Base.promote_op(key, eltype(Is))
-        valtype = Base.promote_op(value, eltype(Is))
-        valtype′ = !isconcretetype(valtype) ? AbstractMatrix{eltype(a)} : valtype
-        Dict{keytype, valtype′}()
-    else
-        Dict(key(I) => value(I) for I in Is)
-    end
+    # Constrain key/value types explicitly so empty cases are still typed.
+    keytype = Base.promote_op(key, eltype(Is))
+    valtype = Base.promote_op(value, eltype(Is))
+    valtype′ = !isconcretetype(valtype) ? AbstractMatrix{eltype(a)} : valtype
+    bs = Dict{keytype, valtype′}(key(I) => value(I) for I in Is)
     return blocksparse(bs, ax)
 end
 
@@ -73,7 +67,12 @@ function TensorAlgebra.unmatricize(
         )
         return unmatricize(reshaped_blocks_m[I], block_axes_I)
     end
-    bs = Dict(key(I) => value(I) for I in eachstoredindex(reshaped_blocks_m))
+    Is = eachstoredindex(reshaped_blocks_m)
+    # Constrain key/value types explicitly so empty cases are still typed.
+    keytype = Base.promote_op(key, eltype(Is))
+    valtype = Base.promote_op(value, eltype(Is))
+    valtype′ = !isconcretetype(valtype) ? AbstractArray{eltype(m), length(ax)} : valtype
+    bs = Dict{keytype, valtype′}(key(I) => value(I) for I in Is)
     return blocksparse(bs, ax)
 end
 
diff --git a/src/abstractblocksparsearray/arraylayouts.jl b/src/abstractblocksparsearray/arraylayouts.jl
index b8329c19..76d9a4ab 100644
--- a/src/abstractblocksparsearray/arraylayouts.jl
+++ b/src/abstractblocksparsearray/arraylayouts.jl
@@ -62,20 +62,26 @@ function ArrayLayouts.sub_materialize(layout::BlockLayout{<:SparseLayout}, a, ax
     # TODO: Use `similar`?
     blocktype_a = blocktype(parent(a))
     a_dest = BlockSparseArray{eltype(a), length(axes), blocktype_a}(undef, axes)
-    for I in SparseArraysBase.eachstoredindex(blocks(a))
-        b = Block(Tuple(I))
-        a_dest[b] = copy(blocks(a)[Tuple(I)...])
-    end
+    a_dest .= a
     return a_dest
 end
 
-function _similar(arraytype::Type{<:AbstractArray}, size::Tuple)
-    return similar(arraytype, size)
+function _similar(arraytype::Type{<:AbstractArray{T, N}}, size::Tuple) where {T, N}
+    if isconcretetype(arraytype)
+        try
+            return similar(arraytype, size)
+        catch err
+            if !(err isa MethodError)
+                rethrow()
+            end
+        end
+    end
+    return similar(Array{T, N}, size)
 end
 function _similar(
         ::Type{<:SubArray{<:Any, <:Any, <:ArrayType}}, size::Tuple
     ) where {ArrayType}
-    return similar(ArrayType, size)
+    return _similar(ArrayType, size)
 end
 
 # Materialize a SubArray view.
@@ -83,6 +89,8 @@ function ArrayLayouts.sub_materialize(
         layout::BlockLayout{<:SparseLayout}, a, axes::Tuple{Vararg{Base.OneTo}}
     )
     a_dest = _similar(blocktype(a), length.(axes))
-    a_dest .= a
+    for I in CartesianIndices(a_dest)
+        @inbounds a_dest[I] = a[I]
+    end
     return a_dest
 end

From 92f88e861b0e5c360dcf0f384446c7c9f9e8d780 Mon Sep 17 00:00:00 2001
From: mtfishman <mfishman@flatironinstitute.org>
Date: Mon, 9 Mar 2026 17:35:35 -0400
Subject: [PATCH 04/15] Simplify

---
 Project.toml                                 |  2 +-
 src/abstractblocksparsearray/arraylayouts.jl | 11 +----------
 2 files changed, 2 insertions(+), 11 deletions(-)

diff --git a/Project.toml b/Project.toml
index ed57ad63..0b15d3ad 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,6 +1,6 @@
 name = "BlockSparseArrays"
 uuid = "2c9a651f-6452-4ace-a6ac-809f4280fbb4"
-version = "0.10.34"
+version = "0.10.35"
 authors = ["ITensor developers <support@itensor.org> and contributors"]
 
 [workspace]
diff --git a/src/abstractblocksparsearray/arraylayouts.jl b/src/abstractblocksparsearray/arraylayouts.jl
index 76d9a4ab..f519798e 100644
--- a/src/abstractblocksparsearray/arraylayouts.jl
+++ b/src/abstractblocksparsearray/arraylayouts.jl
@@ -67,16 +67,7 @@ function ArrayLayouts.sub_materialize(layout::BlockLayout{<:SparseLayout}, a, ax
 end
 
 function _similar(arraytype::Type{<:AbstractArray{T, N}}, size::Tuple) where {T, N}
-    if isconcretetype(arraytype)
-        try
-            return similar(arraytype, size)
-        catch err
-            if !(err isa MethodError)
-                rethrow()
-            end
-        end
-    end
-    return similar(Array{T, N}, size)
+    return isconcretetype(arraytype) ? similar(arraytype, size) : similar(Array{T, N}, size)
 end
 function _similar(
         ::Type{<:SubArray{<:Any, <:Any, <:ArrayType}}, size::Tuple

From 29fb6e8fb4102bf32fd0ffba10c08cbc8c0caa6f Mon Sep 17 00:00:00 2001
From: mtfishman <mfishman@flatironinstitute.org>
Date: Mon, 9 Mar 2026 17:44:53 -0400
Subject: [PATCH 05/15] Bump version

---
 Project.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Project.toml b/Project.toml
index 0b15d3ad..74289e35 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,6 +1,6 @@
 name = "BlockSparseArrays"
 uuid = "2c9a651f-6452-4ace-a6ac-809f4280fbb4"
-version = "0.10.35"
+version = "0.10.36"
 authors = ["ITensor developers <support@itensor.org> and contributors"]
 
 [workspace]

From 6994d05ab4c4a1d22d58c72d79d84cd4f7f41ac5 Mon Sep 17 00:00:00 2001
From: mtfishman <mfishman@flatironinstitute.org>
Date: Mon, 9 Mar 2026 17:48:28 -0400
Subject: [PATCH 06/15] Fix version

---
 Project.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Project.toml b/Project.toml
index 74289e35..0b15d3ad 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,6 +1,6 @@
 name = "BlockSparseArrays"
 uuid = "2c9a651f-6452-4ace-a6ac-809f4280fbb4"
-version = "0.10.36"
+version = "0.10.35"
 authors = ["ITensor developers <support@itensor.org> and contributors"]
 
 [workspace]

From 7ba392b5e73c34f7c27cd0f6b27a742d91a1b180 Mon Sep 17 00:00:00 2001
From: mtfishman <mfishman@flatironinstitute.org>
Date: Mon, 9 Mar 2026 19:08:48 -0400
Subject: [PATCH 07/15] More slicing improvements

---
 src/abstractblocksparsearray/arraylayouts.jl  | 12 ++++-
 .../blocksparsearrayinterface.jl              |  3 +-
 test/test_abstract_blocktype.jl               | 46 ++++++-------------
 3 files changed, 25 insertions(+), 36 deletions(-)

diff --git a/src/abstractblocksparsearray/arraylayouts.jl b/src/abstractblocksparsearray/arraylayouts.jl
index f519798e..10b29c80 100644
--- a/src/abstractblocksparsearray/arraylayouts.jl
+++ b/src/abstractblocksparsearray/arraylayouts.jl
@@ -1,5 +1,5 @@
 using ArrayLayouts: ArrayLayouts, DualLayout, MemoryLayout, MulAdd
-using BlockArrays: BlockLayout
+using BlockArrays: Block, BlockLayout, blocks
 using SparseArraysBase: SparseLayout
 using TypeParameterAccessors: parenttype, similartype
 
@@ -62,7 +62,15 @@ function ArrayLayouts.sub_materialize(layout::BlockLayout{<:SparseLayout}, a, ax
     # TODO: Use `similar`?
     blocktype_a = blocktype(parent(a))
     a_dest = BlockSparseArray{eltype(a), length(axes), blocktype_a}(undef, axes)
-    a_dest .= a
+    for I in CartesianIndices(blocks(a_dest))
+        b = Block(Tuple(I))
+        block_a = @view a[b]
+        if !iszero(block_a)
+            block_dest = similar(a_dest[b])
+            copyto!(block_dest, block_a)
+            a_dest[b] = block_dest
+        end
+    end
     return a_dest
 end
 
diff --git a/src/blocksparsearrayinterface/blocksparsearrayinterface.jl b/src/blocksparsearrayinterface/blocksparsearrayinterface.jl
index 417afb5c..4b2375e0 100644
--- a/src/blocksparsearrayinterface/blocksparsearrayinterface.jl
+++ b/src/blocksparsearrayinterface/blocksparsearrayinterface.jl
@@ -442,8 +442,7 @@ end
 
 # TODO: Define `getstoredindex`, `getunstoredindex` instead.
 function Base.getindex(a::SparseSubArrayBlocks{<:Any, N}, I::Vararg{Int, N}) where {N}
-    # TODO: Should this be defined as `@view a.array[Block(I)]` instead?
-    return @view a.array[Block(I)]
+    return BlockArrays.viewblock(a.array, Block(I))
 
     ## parent_blocks = @view blocks(parent(a.array))[blockrange(a)...]
     ## parent_block = parent_blocks[I...]
diff --git a/test/test_abstract_blocktype.jl b/test/test_abstract_blocktype.jl
index 94d57505..6a05561b 100644
--- a/test/test_abstract_blocktype.jl
+++ b/test/test_abstract_blocktype.jl
@@ -56,36 +56,22 @@ arrayts = (Array, JLArray)
     a = BlockSparseMatrix{elt, AbstractMatrix{elt}}(undef, [2, 3], [2, 3])
     a[Block(1, 1)] = dev(randn(elt, 2, 2))
     for f in (eig_full, eig_trunc)
-        if arrayt === Array
-            d, v = f(a)
-            @test a * v ≈ v * d
-        else
-            @test_broken f(a)
-        end
-    end
-    if arrayt === Array
-        d = eig_vals(a)
-        @test sort(Vector(d); by = abs) ≈ sort(eig_vals(Matrix(a)); by = abs)
-    else
-        @test_broken eig_vals(a)
+        res = f(a)
+        d, v = res[1:2]
+        @test a * v ≈ v * d
     end
+    d = eig_vals(a)
+    @test sort(Vector(d); by = abs) ≈ sort(eig_vals(Matrix(a)); by = abs)
 
     a = BlockSparseMatrix{elt, AbstractMatrix{elt}}(undef, [2, 3], [2, 3])
     a[Block(1, 1)] = dev(parent(hermitianpart(randn(elt, 2, 2))))
     for f in (eigh_full, eigh_trunc)
-        if arrayt === Array
-            d, v = f(a)
-            @test a * v ≈ v * d
-        else
-            @test_broken f(a)
-        end
-    end
-    if arrayt === Array
-        d = eigh_vals(a)
-        @test sort(Vector(d); by = abs) ≈ sort(eig_vals(Matrix(a)); by = abs)
-    else
-        @test_broken eigh_vals(a)
+        res = f(a)
+        d, v = res[1:2]
+        @test a * v ≈ v * d
     end
+    d = eigh_vals(a)
+    @test sort(Vector(d); by = abs) ≈ sort(eig_vals(Matrix(a)); by = abs)
 
     a = BlockSparseMatrix{elt, AbstractMatrix{elt}}(undef, [2, 3], [2, 3])
     a[Block(1, 1)] = dev(randn(elt, 2, 2))
@@ -96,7 +82,7 @@ arrayts = (Array, JLArray)
             @test isisometric(u; side = :left)
         else
             # TODO: Fix comparison with UniformScaling on GPU.
-            @test_broken isisometric(u; side = :left)
+            @test isisometric(u; side = :left)
         end
     end
     for f in (right_orth, right_polar, lq_compact, lq_full)
@@ -106,15 +92,11 @@ arrayts = (Array, JLArray)
             @test isisometric(u; side = :right)
         else
             # TODO: Fix comparison with UniformScaling on GPU.
-            @test_broken isisometric(u; side = :right)
+            @test isisometric(u; side = :right)
         end
     end
     for f in (svd_compact, svd_full, svd_trunc)
-        if arrayt ≢ Array && (f ≡ svd_full || f ≡ svd_trunc)
-            @test_broken f(a)
-        else
-            u, s, v = f(a)
-            @test u * s * v ≈ a
-        end
+        u, s, v = f(a)
+        @test u * s * v ≈ a
     end
 end

From 4e59d57aedf824d7e29245f000bc656b2cf8ade7 Mon Sep 17 00:00:00 2001
From: mtfishman <mfishman@flatironinstitute.org>
Date: Mon, 9 Mar 2026 19:26:45 -0400
Subject: [PATCH 08/15] Mark some tests as fixed

---
 test/test_map.jl | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/test/test_map.jl b/test/test_map.jl
index fcd9f364..8aefed5f 100644
--- a/test/test_map.jl
+++ b/test/test_map.jl
@@ -98,16 +98,14 @@ arrayts = (Array, JLArray)
     @test iszero(storedlength(a))
     @test iszero(b)
     @test iszero(storedlength(b))
-    # TODO: Broken on GPU.
-    @test iszero(c) broken = arrayt ≠ Array
+    @test iszero(c)
     @test iszero(storedlength(c))
     @allowscalar a[5, 7] = 1
     @test !iszero(a)
     @test storedlength(a) == 3 * 4
     @test !iszero(b)
     @test storedlength(b) == 3 * 4
-    # TODO: Broken on GPU.
-    @test !iszero(c) broken = arrayt ≠ Array
+    @test !iszero(c)
     @test storedlength(c) == 3 * 4
     d = @view a[1:4, 1:6]
     @test iszero(d)
@@ -407,12 +405,7 @@ arrayts = (Array, JLArray)
     a[Block(1, 1)] = dev(randn(elt, 2, 2))
     a[Block(2, 2)] = dev(randn(elt, 3, 3))
     I = (:, [2, 4])
-    if arrayt === Array
-        @test Array(a[I...]) == Array(a)[I...]
-    else
-        # TODO: Broken on GPU, fix this.
-        @test_broken a[I...]
-    end
+    @test Array(a[I...]) == Array(a)[I...]
 
     a = BlockSparseArray{elt}(undef, [2, 3], [2, 3])
     @views for b in [Block(1, 1), Block(2, 2)]

From 07d6155f27f9d9adb78ee7e592350e91c3ba982f Mon Sep 17 00:00:00 2001
From: mtfishman <mfishman@flatironinstitute.org>
Date: Mon, 9 Mar 2026 19:57:31 -0400
Subject: [PATCH 09/15] Fix tests

---
 test/test_abstract_blocktype.jl | 30 ++++++++++++++++++++----------
 1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/test/test_abstract_blocktype.jl b/test/test_abstract_blocktype.jl
index 6a05561b..b2783b47 100644
--- a/test/test_abstract_blocktype.jl
+++ b/test/test_abstract_blocktype.jl
@@ -1,6 +1,7 @@
 using Adapt: adapt
 using BlockArrays: Block
 using BlockSparseArrays: BlockSparseMatrix, blockstoredlength
+using GPUArraysCore: allowscalar
 using JLArrays: JLArray
 using LinearAlgebra: hermitianpart, norm
 using MatrixAlgebraKit: eig_full, eig_trunc, eig_vals, eigh_full, eigh_trunc, eigh_vals,
@@ -14,6 +15,7 @@ arrayts = (Array, JLArray)
 @testset "Abstract block type (arraytype=$arrayt, eltype=$elt)" for arrayt in arrayts,
         elt in elts
 
+    arrayt === Array || allowscalar(false)
     dev = adapt(arrayt)
 
     a = BlockSparseMatrix{elt, AbstractMatrix{elt}}(undef, [2, 3], [2, 3])
@@ -56,22 +58,30 @@ arrayts = (Array, JLArray)
     a = BlockSparseMatrix{elt, AbstractMatrix{elt}}(undef, [2, 3], [2, 3])
     a[Block(1, 1)] = dev(randn(elt, 2, 2))
     for f in (eig_full, eig_trunc)
-        res = f(a)
-        d, v = res[1:2]
-        @test a * v ≈ v * d
+        @test begin
+            res = f(a)
+            d, v = res[1:2]
+            a * v ≈ v * d
+        end broken = arrayt ≠ Array
     end
-    d = eig_vals(a)
-    @test sort(Vector(d); by = abs) ≈ sort(eig_vals(Matrix(a)); by = abs)
+    @test begin
+        d = eig_vals(a)
+        sort(Vector(d); by = abs) ≈ sort(eig_vals(Matrix(a)); by = abs)
+    end broken = arrayt ≠ Array
 
     a = BlockSparseMatrix{elt, AbstractMatrix{elt}}(undef, [2, 3], [2, 3])
     a[Block(1, 1)] = dev(parent(hermitianpart(randn(elt, 2, 2))))
     for f in (eigh_full, eigh_trunc)
-        res = f(a)
-        d, v = res[1:2]
-        @test a * v ≈ v * d
+        @test begin
+            res = f(a)
+            d, v = res[1:2]
+            a * v ≈ v * d
+        end broken = arrayt ≠ Array
     end
-    d = eigh_vals(a)
-    @test sort(Vector(d); by = abs) ≈ sort(eig_vals(Matrix(a)); by = abs)
+    @test begin
+        d = eigh_vals(a)
+        sort(Vector(d); by = abs) ≈ sort(eig_vals(Matrix(a)); by = abs)
+    end broken = arrayt ≠ Array
 
     a = BlockSparseMatrix{elt, AbstractMatrix{elt}}(undef, [2, 3], [2, 3])
     a[Block(1, 1)] = dev(randn(elt, 2, 2))

From c80b0cccfb6fa6770d3ff2e6658d56852aa287b3 Mon Sep 17 00:00:00 2001
From: mtfishman <mfishman@flatironinstitute.org>
Date: Mon, 9 Mar 2026 20:10:56 -0400
Subject: [PATCH 10/15] Fix more tests

---
 src/abstractblocksparsearray/arraylayouts.jl |  4 ++--
 test/test_abstract_blocktype.jl              | 14 ++------------
 2 files changed, 4 insertions(+), 14 deletions(-)

diff --git a/src/abstractblocksparsearray/arraylayouts.jl b/src/abstractblocksparsearray/arraylayouts.jl
index 10b29c80..6c7a060e 100644
--- a/src/abstractblocksparsearray/arraylayouts.jl
+++ b/src/abstractblocksparsearray/arraylayouts.jl
@@ -64,8 +64,8 @@ function ArrayLayouts.sub_materialize(layout::BlockLayout{<:SparseLayout}, a, ax
     a_dest = BlockSparseArray{eltype(a), length(axes), blocktype_a}(undef, axes)
     for I in CartesianIndices(blocks(a_dest))
         b = Block(Tuple(I))
-        block_a = @view a[b]
-        if !iszero(block_a)
+        if isstored(a, b)
+            block_a = @view a[b]
             block_dest = similar(a_dest[b])
             copyto!(block_dest, block_a)
             a_dest[b] = block_dest
diff --git a/test/test_abstract_blocktype.jl b/test/test_abstract_blocktype.jl
index b2783b47..7807916c 100644
--- a/test/test_abstract_blocktype.jl
+++ b/test/test_abstract_blocktype.jl
@@ -88,22 +88,12 @@ arrayts = (Array, JLArray)
     for f in (left_orth, left_polar, qr_compact, qr_full)
         u, c = f(a)
         @test u * c ≈ a
-        if arrayt ≡ Array
-            @test isisometric(u; side = :left)
-        else
-            # TODO: Fix comparison with UniformScaling on GPU.
-            @test isisometric(u; side = :left)
-        end
+        @test isisometric(u; side = :left)
     end
     for f in (right_orth, right_polar, lq_compact, lq_full)
         c, u = f(a)
         @test c * u ≈ a
-        if arrayt ≡ Array
-            @test isisometric(u; side = :right)
-        else
-            # TODO: Fix comparison with UniformScaling on GPU.
-            @test isisometric(u; side = :right)
-        end
+        @test isisometric(u; side = :right)
     end
     for f in (svd_compact, svd_full, svd_trunc)
         u, s, v = f(a)

From e296bd2a25e11fb736fbad998f0655aad8b8ace8 Mon Sep 17 00:00:00 2001
From: mtfishman <mfishman@flatironinstitute.org>
Date: Mon, 9 Mar 2026 22:45:45 -0400
Subject: [PATCH 11/15] Remove use of global allowscalar in tests

---
 test/test_abstract_blocktype.jl | 2 --
 1 file changed, 2 deletions(-)

diff --git a/test/test_abstract_blocktype.jl b/test/test_abstract_blocktype.jl
index 7807916c..a3f68e1c 100644
--- a/test/test_abstract_blocktype.jl
+++ b/test/test_abstract_blocktype.jl
@@ -1,7 +1,6 @@
 using Adapt: adapt
 using BlockArrays: Block
 using BlockSparseArrays: BlockSparseMatrix, blockstoredlength
-using GPUArraysCore: allowscalar
 using JLArrays: JLArray
 using LinearAlgebra: hermitianpart, norm
 using MatrixAlgebraKit: eig_full, eig_trunc, eig_vals, eigh_full, eigh_trunc, eigh_vals,
@@ -15,7 +14,6 @@ arrayts = (Array, JLArray)
 @testset "Abstract block type (arraytype=$arrayt, eltype=$elt)" for arrayt in arrayts,
         elt in elts
 
-    arrayt === Array || allowscalar(false)
     dev = adapt(arrayt)
 
     a = BlockSparseMatrix{elt, AbstractMatrix{elt}}(undef, [2, 3], [2, 3])

From f55069afd1eccd9e67a2e6b335da46dffd787125 Mon Sep 17 00:00:00 2001
From: mtfishman <mfishman@flatironinstitute.org>
Date: Mon, 9 Mar 2026 23:06:18 -0400
Subject: [PATCH 12/15] Fix tests

---
 test/test_map.jl | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/test/test_map.jl b/test/test_map.jl
index 8aefed5f..fcd9f364 100644
--- a/test/test_map.jl
+++ b/test/test_map.jl
@@ -98,14 +98,16 @@ arrayts = (Array, JLArray)
     @test iszero(storedlength(a))
     @test iszero(b)
     @test iszero(storedlength(b))
-    @test iszero(c)
+    # TODO: Broken on GPU.
+    @test iszero(c) broken = arrayt ≠ Array
     @test iszero(storedlength(c))
     @allowscalar a[5, 7] = 1
     @test !iszero(a)
     @test storedlength(a) == 3 * 4
     @test !iszero(b)
     @test storedlength(b) == 3 * 4
-    @test !iszero(c)
+    # TODO: Broken on GPU.
+    @test !iszero(c) broken = arrayt ≠ Array
     @test storedlength(c) == 3 * 4
     d = @view a[1:4, 1:6]
     @test iszero(d)
@@ -405,7 +407,12 @@ arrayts = (Array, JLArray)
     a[Block(1, 1)] = dev(randn(elt, 2, 2))
     a[Block(2, 2)] = dev(randn(elt, 3, 3))
     I = (:, [2, 4])
-    @test Array(a[I...]) == Array(a)[I...]
+    if arrayt === Array
+        @test Array(a[I...]) == Array(a)[I...]
+    else
+        # TODO: Broken on GPU, fix this.
+        @test_broken a[I...]
+    end
 
     a = BlockSparseArray{elt}(undef, [2, 3], [2, 3])
     @views for b in [Block(1, 1), Block(2, 2)]

From a44bb7d3942636d3b814b5e041c798a105f43975 Mon Sep 17 00:00:00 2001
From: mtfishman <mfishman@flatironinstitute.org>
Date: Mon, 9 Mar 2026 23:29:50 -0400
Subject: [PATCH 13/15] Cleanup

---
 .../BlockSparseArraysTensorAlgebraExt.jl      | 31 +++++++++++++------
 src/abstractblocksparsearray/arraylayouts.jl  | 18 +++++------
 2 files changed, 28 insertions(+), 21 deletions(-)

diff --git a/ext/BlockSparseArraysTensorAlgebraExt/BlockSparseArraysTensorAlgebraExt.jl b/ext/BlockSparseArraysTensorAlgebraExt/BlockSparseArraysTensorAlgebraExt.jl
index 917119df..c13734f1 100644
--- a/ext/BlockSparseArraysTensorAlgebraExt/BlockSparseArraysTensorAlgebraExt.jl
+++ b/ext/BlockSparseArraysTensorAlgebraExt/BlockSparseArraysTensorAlgebraExt.jl
@@ -41,11 +41,17 @@ function TensorAlgebra.matricize(
     key(I) = Block(Tuple(I))
     value(I) = matricize(reshaped_blocks_a[I], length_codomain)
     Is = eachstoredindex(reshaped_blocks_a)
-    # Constrain key/value types explicitly so empty cases are still typed.
-    keytype = Base.promote_op(key, eltype(Is))
-    valtype = Base.promote_op(value, eltype(Is))
-    valtype′ = !isconcretetype(valtype) ? AbstractMatrix{eltype(a)} : valtype
-    bs = Dict{keytype, valtype′}(key(I) => value(I) for I in Is)
+    bs = if isempty(Is)
+        # Catch empty case and make sure the type is constrained properly.
+        # This seems to only be necessary in Julia versions below v1.11,
+        # try removing it when we drop support for those versions.
+        keytype = Base.promote_op(key, eltype(Is))
+        valtype = Base.promote_op(value, eltype(Is))
+        valtype′ = !isconcretetype(valtype) ? AbstractMatrix{eltype(a)} : valtype
+        Dict{keytype, valtype′}()
+    else
+        Dict(key(I) => value(I) for I in Is)
+    end
     return blocksparse(bs, ax)
 end
 
@@ -68,11 +74,16 @@ function TensorAlgebra.unmatricize(
         return unmatricize(reshaped_blocks_m[I], block_axes_I)
     end
     Is = eachstoredindex(reshaped_blocks_m)
-    # Constrain key/value types explicitly so empty cases are still typed.
-    keytype = Base.promote_op(key, eltype(Is))
-    valtype = Base.promote_op(value, eltype(Is))
-    valtype′ = !isconcretetype(valtype) ? AbstractArray{eltype(m), length(ax)} : valtype
-    bs = Dict{keytype, valtype′}(key(I) => value(I) for I in Is)
+    bs = if isempty(Is)
+        # Constrain key/value types explicitly so empty cases are still typed.
+        keytype = Base.promote_op(key, eltype(Is))
+        valtype = Base.promote_op(value, eltype(Is))
+        valtype′ =
+            !isconcretetype(valtype) ? AbstractArray{eltype(m), length(ax)} : valtype
+        bs = Dict{keytype, valtype′}(key(I) => value(I) for I in Is)
+    else
+        Dict(key(I) => value(I) for I in eachstoredindex(reshaped_blocks_m))
+    end
     return blocksparse(bs, ax)
 end
 
diff --git a/src/abstractblocksparsearray/arraylayouts.jl b/src/abstractblocksparsearray/arraylayouts.jl
index 6c7a060e..921488e9 100644
--- a/src/abstractblocksparsearray/arraylayouts.jl
+++ b/src/abstractblocksparsearray/arraylayouts.jl
@@ -1,6 +1,6 @@
 using ArrayLayouts: ArrayLayouts, DualLayout, MemoryLayout, MulAdd
 using BlockArrays: Block, BlockLayout, blocks
-using SparseArraysBase: SparseLayout
+using SparseArraysBase: SparseLayout, eachstoredindex
 using TypeParameterAccessors: parenttype, similartype
 
 function ArrayLayouts.MemoryLayout(arraytype::Type{<:AnyAbstractBlockSparseArray})
@@ -62,14 +62,12 @@ function ArrayLayouts.sub_materialize(layout::BlockLayout{<:SparseLayout}, a, ax
     # TODO: Use `similar`?
     blocktype_a = blocktype(parent(a))
     a_dest = BlockSparseArray{eltype(a), length(axes), blocktype_a}(undef, axes)
-    for I in CartesianIndices(blocks(a_dest))
+    for I in eachstoredindex(blocks(a))
         b = Block(Tuple(I))
-        if isstored(a, b)
-            block_a = @view a[b]
-            block_dest = similar(a_dest[b])
-            copyto!(block_dest, block_a)
-            a_dest[b] = block_dest
-        end
+        block_a = @view a[b]
+        block_dest = similar(a_dest[b])
+        copyto!(block_dest, block_a)
+        a_dest[b] = block_dest
     end
     return a_dest
 end
@@ -88,8 +86,6 @@ function ArrayLayouts.sub_materialize(
         layout::BlockLayout{<:SparseLayout}, a, axes::Tuple{Vararg{Base.OneTo}}
     )
     a_dest = _similar(blocktype(a), length.(axes))
-    for I in CartesianIndices(a_dest)
-        @inbounds a_dest[I] = a[I]
-    end
+    copyto!(a_dest, a)
     return a_dest
 end

From d627bb104e52b2242b135196640e42a12016b835 Mon Sep 17 00:00:00 2001
From: mtfishman <mfishman@flatironinstitute.org>
Date: Tue, 10 Mar 2026 07:19:41 -0400
Subject: [PATCH 14/15] Fix tests with non-ideal loop in sub_materialize

---
 src/abstractblocksparsearray/arraylayouts.jl | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/src/abstractblocksparsearray/arraylayouts.jl b/src/abstractblocksparsearray/arraylayouts.jl
index 921488e9..edd87da5 100644
--- a/src/abstractblocksparsearray/arraylayouts.jl
+++ b/src/abstractblocksparsearray/arraylayouts.jl
@@ -1,6 +1,6 @@
 using ArrayLayouts: ArrayLayouts, DualLayout, MemoryLayout, MulAdd
 using BlockArrays: Block, BlockLayout, blocks
-using SparseArraysBase: SparseLayout, eachstoredindex
+using SparseArraysBase: SparseLayout
 using TypeParameterAccessors: parenttype, similartype
 
 function ArrayLayouts.MemoryLayout(arraytype::Type{<:AnyAbstractBlockSparseArray})
@@ -62,12 +62,14 @@ function ArrayLayouts.sub_materialize(layout::BlockLayout{<:SparseLayout}, a, ax
     # TODO: Use `similar`?
     blocktype_a = blocktype(parent(a))
     a_dest = BlockSparseArray{eltype(a), length(axes), blocktype_a}(undef, axes)
-    for I in eachstoredindex(blocks(a))
+    for I in CartesianIndices(blocks(a_dest))
         b = Block(Tuple(I))
-        block_a = @view a[b]
-        block_dest = similar(a_dest[b])
-        copyto!(block_dest, block_a)
-        a_dest[b] = block_dest
+        if isstored(a, b)
+            block_a = @view a[b]
+            block_dest = similar(a_dest[b])
+            copyto!(block_dest, block_a)
+            a_dest[b] = block_dest
+        end
     end
     return a_dest
 end

From 79ebb14f1dea4506226a9146cfbf9f1645408fe5 Mon Sep 17 00:00:00 2001
From: mtfishman <mfishman@flatironinstitute.org>
Date: Tue, 10 Mar 2026 10:13:37 -0400
Subject: [PATCH 15/15] Small simplification in blockless unmatricize

---
 .../BlockSparseArraysTensorAlgebraExt.jl                        | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ext/BlockSparseArraysTensorAlgebraExt/BlockSparseArraysTensorAlgebraExt.jl b/ext/BlockSparseArraysTensorAlgebraExt/BlockSparseArraysTensorAlgebraExt.jl
index c13734f1..c5b74c7c 100644
--- a/ext/BlockSparseArraysTensorAlgebraExt/BlockSparseArraysTensorAlgebraExt.jl
+++ b/ext/BlockSparseArraysTensorAlgebraExt/BlockSparseArraysTensorAlgebraExt.jl
@@ -80,7 +80,7 @@ function TensorAlgebra.unmatricize(
         valtype = Base.promote_op(value, eltype(Is))
         valtype′ =
             !isconcretetype(valtype) ? AbstractArray{eltype(m), length(ax)} : valtype
-        bs = Dict{keytype, valtype′}(key(I) => value(I) for I in Is)
+        bs = Dict{keytype, valtype′}()
     else
         Dict(key(I) => value(I) for I in eachstoredindex(reshaped_blocks_m))
     end