[ITensors] [ENHANCEMENT] Fix directsum when specifying a single `In…

…dex` (#930)

ITensorUnicodePlots/test/references/R.txt

@@ -3,18 +3,18 @@
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ERn2⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
-    ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⠔⠁⡇⠑⠢⣀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
+    ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⠕⠀⡇⠑⠢⣀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡠⠊(20)'⠀⠑⠢⣀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀20⠊⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀10⠢⢄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡠⠊⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠉⠢⢄⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡠⠊⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣀⣉hn2⠀⠀⠀⠀
-    ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⠜⠀⣀⣀⣀⣀⣀⡠⠤⠤⠤⠤2⠒⠒⠒⠒⠒⠉⠉⠉⠉⠉⠀⢀⠔⢹⠀⠀⠀⠀⠀
+    ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⠜⠀⣀⣀⣀⣀⣀⡠⠤⠤⠠⠤2⠒⠒⠒⠒⠒⠉⠉⠉⠉⠉⠀⢀⠔⢹⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ψn1n2⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⠔(2)'⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡠⠊⠁⠀⠀⠀⠀⠉⠢⢄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀10⠔⠁⠀⠀⠀⢸⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⡠⠊⠀⠀⠀⠀⠀⠀⠀⠀⠀2⊗2⊗2⠀⠀⠀⠀⠀⠀⠀⠀⠀⡠⠒⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
-    ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀20⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⠒⢄⡀⠀⠀⠀⠀⡠⠊⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
+    ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀20⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⠖⢀⡀⠀⠀⠀⠀⡠⠊⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⡠⠔⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢈⣑hn1⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
-    ⠀⠀⠀⠀⠀⠀⡠⠊⠀⠀⢀⣀⣀⣀⣀⡠⠤⠤10⠤⠒⠒⠒⠒⠒⠉⠉⠉⠉⠉⠁⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
+    ⠀⠀⠀⠀⠀⠀⡠⠊⠀⠀⢀⣀⣀⣀⣀⡠⠤⠤10⠤⠒⠒⠒⠒⠒⠉⠉⠉⠉⠈⠁⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀ELn0⠉⠉⠉⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀(2)'⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀(20)'⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

ITensorUnicodePlots/test/references/R1.txt

@@ -5,7 +5,7 @@
     ⠀⠀⠀ELn0⣀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⣷⠀⠀⠉⠉⠑⠒⠒⠤⠤⢄⣀⣀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⡇⢇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠉⠉⠑⠒⠒⠤⠤10⣀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
-    ⠀⠀⠀(20)'⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠉⠉⠉⠒⠒⠢⠤⠤⣀⣀⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
+    ⠀⠀⠀(20)'⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠉⠉⠈⠒⠒⠢⠤⠤⣀⣀⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⡇⠀⢱⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⠉⠉⠒⠒⠢⠤hn1⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⡇⠀⠀⢇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣀⠤⠒⠉⢸⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠁⠀⠀⠘⡄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⡠⠒⠉⠀⠀⠀⠀⢸⠀⠀⠀⠀⠀

ITensorUnicodePlots/test/references/R2.txt

@@ -5,7 +5,7 @@
     ⠀⠀⠀⠀T1⣀⣀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⣷⠀⠀⠉⠉⠑⠒⠒⠤⠤⢄⣀⣀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⡇⢇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠉⠉⠑⠒⠒⠤⠤20⣀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
-    ⠀20)'⊗(2)'⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠉⠉⠉⠒⠒⠢⠤⠤⣀⣀⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
+    ⠀20)'⊗(2)'⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠉⠉⠈⠒⠒⠢⠤⠤⣀⣀⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⡇⠀⢱⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⠉⠉⠒⠒⠢⠤T3⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⡇⠀⠀⢇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣀⠤⠒⠉⢸⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠁⠀⠀⠘⡄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⡠⠒⠉⠀⠀⠀⠀⢸⠀⠀⠀⠀⠀

ITensorUnicodePlots/test/references/R_tags.txt

@@ -3,7 +3,7 @@
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ERn2⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
-    ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⠔⠁⡇⠑⠢⣀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
+    ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⠕⠀⡇⠑⠢⣀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀(20|"Link,l=3")'⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀(20|"Link,l(10|"Link,ham,l=3")⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡠⠊⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠉⠢⢄⠀⠀⠀⠀⠀⠀⠀⠀
@@ -12,9 +12,9 @@
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ψn1n2⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀(2|"S=1/2,Site,⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡠⠊⠁⠀⠀⠀⠀⠉⠢⢄⠀⠀⠀⠀⠀⠀(10|"Link,ham,l=2")⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀(2|"S=1/2,Site,n=2")⊗(2|"X")⊗(2|"Y")⠀⠀⠀⠀⠀⠀⠀⠀
-    ⠀⠀⠀⠀⠀(20|"Link,l=1")⠀⠀⠀⠀⠀⠀⠀⠀⠈⠒⢄⡀⠀⠀⠀⠀⡠⠊⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
+    ⠀⠀⠀⠀⠀(20|"Link,l=1")⠀⠀⠀⠀⠀⠀⠀⠀⠈⠖⢀⡀⠀⠀⠀⠀⡠⠊⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⡠⠔⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢈⣑hn1⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
-    ⠀⠀⠀⠀⠀⠀⡠⠊⠀⠀(10|"Link,ham,l=1")⠉⠉⠁⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
+    ⠀⠀⠀⠀⠀⠀⡠⠊⠀⠀(10|"Link,ham,l=1")⠉⠈⠁⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀ELn0⠉⠉⠉⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀(2|"S=1/2,Site,n=2")'⠀⠀⠀⠀⠀⠀⠀
     ⠀"Link,l=1")'⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

ITensorUnicodePlots/test/references/tn.txt

@@ -3,18 +3,18 @@
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀tn₅⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
-    ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⠔⠁⡇⠑⠢⣀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
+    ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⠕⠀⡇⠑⠢⣀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡠⠊(20)'⠀⠑⠢⣀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀20⠊⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀10⠢⢄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡠⠊⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠉⠢⢄⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡠⠊⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣀⣉tn₄⠀⠀⠀⠀
-    ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⠜⠀⣀⣀⣀⣀⣀⡠⠤⠤⠤⠤2⠒⠒⠒⠒⠒⠉⠉⠉⠉⠉⠀⢀⠔⢹⠀⠀⠀⠀⠀
+    ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⠜⠀⣀⣀⣀⣀⣀⡠⠤⠤⠠⠤2⠒⠒⠒⠒⠒⠉⠉⠉⠉⠉⠀⢀⠔⢹⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀tn₂⣉⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⠔(2)'⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡠⠊⠁⠀⠀⠀⠀⠉⠢⢄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀10⠔⠁⠀⠀⠀⢸⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⡠⠊⠀⠀⠀⠀⠀⠀⠀⠀⠀2⊗2⊗2⠀⠀⠀⠀⠀⠀⠀⠀⠀⡠⠒⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
-    ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀20⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⠒⢄⡀⠀⠀⠀⠀⡠⠊⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
+    ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀20⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⠖⢀⡀⠀⠀⠀⠀⡠⠊⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⠀⠀⠀⡠⠔⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢈⣑tn₃⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
-    ⠀⠀⠀⠀⠀⠀⡠⠊⠀⠀⢀⣀⣀⣀⣀⡠⠤⠤10⠤⠒⠒⠒⠒⠒⠉⠉⠉⠉⠉⠁⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
+    ⠀⠀⠀⠀⠀⠀⡠⠊⠀⠀⢀⣀⣀⣀⣀⡠⠤⠤10⠤⠒⠒⠒⠒⠒⠉⠉⠉⠉⠈⠁⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀tn₁⠉⠉⠉⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀(2)'⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀(20)'⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
     ⠀⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

src/exports.jl

@@ -117,6 +117,7 @@ export
   ITensor,
   # Methods
   ⊙,
+  ⊕,
   addtags!,
   apply,
   Apply,
@@ -136,6 +137,7 @@ export
   δ,
   diagitensor,
   diagITensor,
+  directsum,
   dot,
   eachnzblock,
   firstind,

src/itensor.jl

@@ -2270,16 +2270,79 @@ function directsum_itensors(i::Index, j::Index, ij::Index)
   return D1, D2
 end
 
+function check_directsum_inds(A::ITensor, I, B::ITensor, J)
+  a = uniqueinds(A, I)
+  b = uniqueinds(B, J)
+  if !hassameinds(a, b)
+    error("""In directsum, attemptying to direct sum ITensors A and B with indices:
+
+          $(inds(A))
+
+          and
+
+          $(inds(B))
+
+          over the indices
+
+          $(I)
+
+          and
+
+          $(J)
+
+          The indices not being direct summed must match, however they are
+
+          $a
+
+          and
+
+          $b
+          """)
+  end
+end
+
+function _directsum(A::ITensor, I, B::ITensor, J; tags=["sum$i" for i in 1:length(I)])
+  N = length(I)
+  (N != length(J)) &&
+    error("In directsum(::ITensor, ::ITensor, ...), must sum equal number of indices")
+  check_directsum_inds(A, I, B, J)
+  IJ = Vector{Base.promote_eltype(I, J)}(undef, N)
+  for n in 1:N
+    In = I[n]
+    Jn = J[n]
+    In = dir(A, In) != dir(In) ? dag(In) : In
+    Jn = dir(B, Jn) != dir(Jn) ? dag(Jn) : Jn
+    IJn = directsum(In, Jn; tags=tags[n])
+    D1, D2 = directsum_itensors(In, Jn, IJn)
+    IJ[n] = IJn
+    A *= D1
+    B *= D2
+  end
+  C = A + B
+  return C => IJ
+end
+
+function _directsum(A::ITensor, i::Index, B::ITensor, j::Index; tags="sum")
+  C, (ij,) = _directsum(A, (i,), B, (j,); tags=[tags])
+  return C => ij
+end
+
 function directsum(A_and_I::Pair{ITensor}, B_and_J::Pair{ITensor}; kwargs...)
-  A, I = A_and_I
-  B, J = B_and_J
-  return directsum(A, B, I, J; kwargs...)
+  return _directsum(A_and_I..., B_and_J...; kwargs...)
+end
+
+function default_directsum_tags(A_and_I::Pair{ITensor})
+  return ["sum$i" for i in 1:length(last(A_and_I))]
+end
+
+function default_directsum_tags(A_and_I::Pair{ITensor,<:Index})
+  return "sum"
 end
 
 """
     directsum(A::Pair{ITensor}, B::Pair{ITensor}, ...; tags)
 
-Given a list of pairs of ITensors and collections of indices, perform a partial
+Given a list of pairs of ITensors and indices, perform a partial
 direct sum of the tensors over the specified indices. Indices that are
 not specified to be summed must match between the tensors.
 
@@ -2301,42 +2364,34 @@ j1 = Index(4, "j1")
 i2 = Index(5, "i2")
 j2 = Index(6, "j2")
 
+A1 = randomITensor(x, i1)
+A2 = randomITensor(x, i2)
+S, s = directsum(A1 => i1, A2 => i2)
+dim(s) == dim(i1) + dim(i2)
+
+A3 = randomITensor(x, j1)
+S, s = directsum(A1 => i1, A2 => i2, A3 => j1)
+dim(s) == dim(i1) + dim(i2) + dim(j1)
+
 A1 = randomITensor(i1, x, j1)
 A2 = randomITensor(x, j2, i2)
-S, s = ITensors.directsum(A1 => (i1, j1), A2 => (i2, j2); tags = ["sum_i", "sum_j"])
+S, s = directsum(A1 => (i1, j1), A2 => (i2, j2); tags = ["sum_i", "sum_j"])
+length(s) == 2
+dim(s[1]) == dim(i1) + dim(i2)
+dim(s[2]) == dim(j1) + dim(j2)
 ```
 """
 function directsum(
   A_and_I::Pair{ITensor},
   B_and_J::Pair{ITensor},
   C_and_K::Pair{ITensor},
   itensor_and_inds...;
-  tags=["sum$i" for i in 1:length(last(A_and_I))],
+  tags=default_directsum_tags(A_and_I),
 )
-  return directsum(
-    Pair(directsum(A_and_I, B_and_J; tags)...), C_and_K, itensor_and_inds...; tags
-  )
+  return directsum(directsum(A_and_I, B_and_J; tags), C_and_K, itensor_and_inds...; tags)
 end
 
-function directsum(A::ITensor, B::ITensor, I, J; tags)
-  N = length(I)
-  (N != length(J)) &&
-    error("In directsum(::ITensor, ::ITensor, ...), must sum equal number of indices")
-  IJ = Vector{Base.promote_eltype(I, J)}(undef, N)
-  for n in 1:N
-    In = I[n]
-    Jn = J[n]
-    In = dir(A, In) != dir(In) ? dag(In) : In
-    Jn = dir(B, Jn) != dir(Jn) ? dag(Jn) : Jn
-    IJn = directsum(In, Jn; tags=tags[n])
-    D1, D2 = directsum_itensors(In, Jn, IJn)
-    IJ[n] = IJn
-    A *= D1
-    B *= D2
-  end
-  C = A + B
-  return C, IJ
-end
+const ⊕ = directsum
 
 """
     apply(A::ITensor, B::ITensor)

src/physics/fermions.jl

@@ -79,7 +79,9 @@ according to p, then return -1. Otherwise return +1.
 function compute_permfactor(p, iv_or_qn...; range=1:length(iv_or_qn))::Int
   using_auto_fermion() || return 1
   N = length(iv_or_qn)
-  oddp = @MVector zeros(Int, N)
+  # XXX: Bug https://github.com/ITensor/ITensors.jl/issues/931
+  # oddp = @MVector zeros(Int, N)
+  oddp = MVector((ntuple(Returns(0), Val(N))))
   n = 0
   @inbounds for j in range
     if fparity(iv_or_qn[p[j]]) == 1

test/itensor.jl

@@ -1627,6 +1627,49 @@ end
         end
       end
     end
+
+    i1, i2, j, k, l = Index.((2, 3, 4, 5, 6), ("i1", "i2", "j", "k", "l"))
+
+    A = randomITensor(i1, i2, j)
+    B = randomITensor(i1, i2, k)
+    C = randomITensor(i1, i2, l)
+
+    S, s = directsum(A => j, B => k)
+    @test dim(s) == dim(j) + dim(k)
+    @test hassameinds(S, (i1, i2, s))
+
+    S, s = (A => j) ⊕ (B => k)
+    @test dim(s) == dim(j) + dim(k)
+    @test hassameinds(S, (i1, i2, s))
+
+    S, s = directsum(A => j, B => k, C => l)
+    @test dim(s) == dim(j) + dim(k) + dim(l)
+    @test hassameinds(S, (i1, i2, s))
+
+    @test_throws ErrorException directsum(A => i2, B => i2)
+
+    S, (s,) = directsum(A => (j,), B => (k,))
+    @test s == uniqueind(S, A)
+    @test dim(s) == dim(j) + dim(k)
+    @test hassameinds(S, (i1, i2, s))
+
+    S, ss = directsum(A => (i2, j), B => (i2, k))
+    @test length(ss) == 2
+    @test dim(ss[1]) == dim(i2) + dim(i2)
+    @test hassameinds(S, (i1, ss...))
+
+    S, ss = directsum(A => (j,), B => (k,), C => (l,))
+    s = only(ss)
+    @test s == uniqueind(S, A)
+    @test dim(s) == dim(j) + dim(k) + dim(l)
+    @test hassameinds(S, (i1, i2, s))
+
+    S, ss = directsum(A => (i2, i1, j), B => (i1, i2, k), C => (i1, i2, l))
+    @test length(ss) == 3
+    @test dim(ss[1]) == dim(i2) + dim(i1) + dim(i1)
+    @test dim(ss[2]) == dim(i1) + dim(i2) + dim(i2)
+    @test dim(ss[3]) == dim(j) + dim(k) + dim(l)
+    @test hassameinds(S, ss)
   end
 
   @testset "ishermitian" begin