Many fixes

src/contract.jl

@@ -117,7 +117,7 @@ function projcontract(
     end
 
     if length(results) == 1
-        return results[1]
+        return results
     end
 
     res = if length(patchorder) > 0

src/partitionedmps.jl

@@ -6,6 +6,7 @@ struct PartitionedMPS
     data::OrderedDict{Projector,SubDomainMPS}
 
     function PartitionedMPS(data::AbstractVector{SubDomainMPS})
+        length(data) > 0 || error("Empty data")
         sites_all = [siteinds(prjmps) for prjmps in data]
         for n in 2:length(data)
             Set(sites_all[n]) == Set(sites_all[1]) || error("Sitedims mismatch")
@@ -32,9 +33,10 @@ end
 ITensors.siteinds(obj::PartitionedMPS) = siteindices(obj)
 
 """
-Get the number of sites in the PartitionedMPS
+Get the number of the data in the PartitionedMPS.
+This is NOT the number of sites in the PartitionedMPS.
 """
-Base.length(obj::PartitionedMPS) = length(first(obj.data))
+Base.length(obj::PartitionedMPS) = length(obj.data)
 
 """
 Indexing for PartitionedMPS. This is deprecated and will be removed in the future.

src/projector.jl

@@ -30,7 +30,9 @@ Projector(singleproj::Pair{Index{T},Int}) where {T} =
     Projector(Dict{Index,Int}(singleproj.first => singleproj.second))
 
 function Base.hash(p::Projector, h::UInt)
-    tmp = hash(collect(Iterators.flatten(((hash(k, h), hash(v, h)) for (k, v) in p.data))))
+    tmp = hash(
+        sort(collect(Iterators.flatten(((hash(k, h), hash(v, h)) for (k, v) in p.data))))
+    )
     return Base.hash(tmp, h)
 end
 

test/partitionedmps_tests.jl

@@ -1,10 +1,11 @@
 using Test
 
 using ITensors
+using ITensorMPS
 
 import PartitionedMPSs: Projector, project, SubDomainMPS, PartitionedMPS
 
-@testset "PartitionedMPS.jl" begin
+@testset "partitionedmps.jl" begin
     @testset "two blocks" begin
         N = 3
         sitesx = [Index(2, "x=$n") for n in 1:N]
@@ -22,6 +23,10 @@ import PartitionedMPSs: Projector, project, SubDomainMPS, PartitionedMPS
         @test_throws ErrorException PartitionedMPS([prjΨ, prjΨ1])
         @test_throws ErrorException PartitionedMPS([prjΨ1, prjΨ1])
 
+        # Iterator and length
+        @test length(PartitionedMPS(prjΨ1)) == 1
+        @test length([(k, v) for (k, v) in PartitionedMPS(prjΨ1)]) == 1
+
         Ψreconst = PartitionedMPS(prjΨ1) + PartitionedMPS(prjΨ2)
         @test Ψreconst[1] == prjΨ1
         @test Ψreconst[2] == prjΨ2