[NDTensors] Fix isempty(::Tensor) (#1401)

Author: mtfishman

Checklists.txt

@@ -14,9 +14,6 @@ Checklist for Tagging a New Release
   automatically (if you see a notice about "Trigger TagBot Issue"
   it does not mean that TagBot isn't working or has an issue, it
   is just literally a Github issue used to trigger TagBot to run)
-- TagBot helpfully explains the differences from the previous
-  versions in the Github version entry. This can be useful for
-  updating the NEWS.md file.
 
 Checklist for Updating the Version of Documenter.jl Used
 ----------------------------------------------------------

NDTensors/NEWS.md

@@ -1,7 +1,7 @@
 name = "NDTensors"
 uuid = "23ae76d9-e61a-49c4-8f12-3f1a16adf9cf"
 authors = ["Matthew Fishman <[email protected]>"]
-version = "0.3.1"
+version = "0.3.2"
 
 [deps]
 Accessors = "7d9f7c33-5ae7-4f3b-8dc6-eff91059b697"

NDTensors/Project.toml

@@ -277,8 +277,6 @@ array(T::Tensor) = array(dense(T))
 matrix(T::Tensor{<:Number,2}) = array(T)
 vector(T::Tensor{<:Number,1}) = array(T)
 
-isempty(T::Tensor) = isempty(storage(T))
-
 #
 # Helper functions for BlockSparse-type storage
 #

NDTensors/src/tensor/tensor.jl

@@ -1,10 +1,28 @@
 @eval module $(gensym())
-using NDTensors
-using LinearAlgebra: Hermitian, exp, svd
-using Test: @testset, @test, @test_throws
 using GPUArraysCore: @allowscalar
+using LinearAlgebra: Hermitian, exp, norm, svd
+using NDTensors:
+  NDTensors,
+  BlockSparseTensor,
+  array,
+  blockdims,
+  blockoffsets,
+  blockview,
+  data,
+  dense,
+  dims,
+  eachnzblock,
+  inds,
+  isblocknz,
+  nnz,
+  nnzblocks,
+  randomBlockSparseTensor,
+  store,
+  storage
 include("NDTensorsTestUtils/NDTensorsTestUtils.jl")
 using .NDTensorsTestUtils: default_rtol, devices_list, is_supported_eltype
+using Random: randn!
+using Test: @test, @test_throws, @testset
 
 @testset "BlockSparseTensor basic functionality" begin
   C = nothing
@@ -26,6 +44,7 @@ using .NDTensorsTestUtils: default_rtol, devices_list, is_supported_eltype
 
     @test blockdims(A, (1, 2)) == (2, 5)
     @test blockdims(A, (2, 1)) == (3, 4)
+    @test !isempty(A)
     @test nnzblocks(A) == 2
     @test nnz(A) == 2 * 5 + 3 * 4
     @test inds(A) == ([2, 3], [4, 5])
@@ -102,6 +121,30 @@ using .NDTensorsTestUtils: default_rtol, devices_list, is_supported_eltype
     @test conj(data(store(A))) == data(store(conj(A)))
     @test typeof(conj(A)) <: BlockSparseTensor
 
+    @testset "No blocks" begin
+      T = dev(BlockSparseTensor{elt}(Tuple{Int,Int}[], [2, 2], [2, 2]))
+      @test nnzblocks(T) == 0
+      @test size(T) == (4, 4)
+      @test length(T) == 16
+      @test !isempty(T)
+      @test isempty(storage(T))
+      @test nnz(T) == 0
+      @test eltype(T) == elt
+      @test norm(T) == 0
+    end
+
+    @testset "Empty" begin
+      T = dev(BlockSparseTensor{elt}(Tuple{Int,Int}[], Int[], Int[]))
+      @test nnzblocks(T) == 0
+      @test size(T) == (0, 0)
+      @test length(T) == 0
+      @test isempty(T)
+      @test isempty(storage(T))
+      @test nnz(T) == 0
+      @test eltype(T) == elt
+      @test norm(T) == 0
+    end
+
     @testset "Random constructor" begin
       T = dev(randomBlockSparseTensor(elt, [(1, 1), (2, 2)], ([2, 2], [2, 2])))
       @test nnzblocks(T) == 2

NDTensors/test/test_blocksparse.jl

@@ -6,7 +6,7 @@ The main breaking changes in ITensor.jl v0.2 involve changes to the `ITensor`, `
 
 In addition, we have moved development of NDTensors.jl into ITensors.jl to simplify the development process until NDTensors is more stable and can be a standalone package. Again, see below for more details.
 
-For a more comprehensive list of changes, see the [change log](https://github.com/ITensor/ITensors.jl/blob/main/NEWS.md) and the [commit history on Github](https://github.com/ITensor/ITensors.jl/commits/main).
+For a more comprehensive list of changes, see the [commit history on Github](https://github.com/ITensor/ITensors.jl/commits/main).
 
 If you have issues upgrading, please reach out by [raising an issue on Github](https://github.com/ITensor/ITensors.jl/issues/new) or asking a question on the [ITensor support forum](http://itensor.org/support/).
 

docs/src/UpgradeGuide_0.1_to_0.2.md

@@ -35,8 +35,7 @@ Development of ITensor is supported by the Flatiron Institute, a division of the
 
 -  Jun 09, 2021: ITensors.jl v0.2 has been released, with a few breaking changes as well as a variety of bug fixes
 and new features. Take a look at the [upgrade guide](https://itensor.github.io/ITensors.jl/stable/UpgradeGuide_0.1_to_0.2.html)
-for help upgrading your code as well as the [change log](https://github.com/ITensor/ITensors.jl/blob/main/NEWS.md)
-for a comprehensive list of changes.
+for help upgrading your code.
 
 ## Installation