Add tests for TruncationUnion and minrank

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: lkdvos

test/testsuite/decompositions/svd.jl

@@ -212,6 +212,29 @@ function test_svd_trunc(
                 @test diagview(S2) ≈ diagview(S)[1:2]
             end
         end
+        @testset "mix minrank and tol" begin
+            m4 = 4
+            U = instantiate_unitary(T, A, m4)
+            Sdiag = similar(A, real(eltype(T)), m4)
+            copyto!(Sdiag, [0.9, 0.3, 0.1, 0.01])
+            S = Diagonal(Sdiag)
+            Vᴴ = instantiate_unitary(T, A, m4)
+            A = U * S * Vᴴ
+            for trunc_fun in (
+                    (rtol, minrank) -> (; rtol, minrank),
+                    (rtol, minrank) -> trunctol(; rtol) | truncrank(minrank),
+                )
+                # trunctol(rtol=0.5) keeps 1 value, truncrank(3) keeps 3, union keeps 3
+                U1, S1, V1ᴴ, ϵ1 = svd_trunc(A; trunc = trunc_fun(0.5, 3))
+                @test length(diagview(S1)) == 3
+                @test diagview(S1) ≈ diagview(S)[1:3]
+
+                # trunctol(rtol=0.2) keeps 2 values, truncrank(1) keeps 1, union keeps 2
+                U2, S2, V2ᴴ = svd_trunc_no_error(A; trunc = trunc_fun(0.2, 1))
+                @test length(diagview(S2)) == 2
+                @test diagview(S2) ≈ diagview(S)[1:2]
+            end
+        end
         @testset "specify truncation algorithm" begin
             atol = sqrt(eps(real(eltype(T))))
             m4 = 4
@@ -294,6 +317,29 @@ function test_svd_trunc_algs(
                 @test collect(diagview(S2)) ≈ collect(diagview(S)[1:2])
             end
         end
+        @testset "mix minrank and tol" begin
+            m4 = 4
+            U = instantiate_unitary(T, A, m4)
+            Sdiag = similar(A, real(eltype(T)), m4)
+            copyto!(Sdiag, real(eltype(T))[0.9, 0.3, 0.1, 0.01])
+            S = Diagonal(Sdiag)
+            Vᴴ = instantiate_unitary(T, A, m4)
+            A = U * S * Vᴴ
+            for trunc_fun in (
+                    (rtol, minrank) -> (; rtol, minrank),
+                    (rtol, minrank) -> trunctol(; rtol) | truncrank(minrank),
+                )
+                # trunctol(rtol=0.5) keeps 1 value, truncrank(3) keeps 3, union keeps 3
+                U1, S1, V1ᴴ, ϵ1 = svd_trunc(A; trunc = trunc_fun(0.5, 3), alg)
+                @test length(diagview(S1)) == 3
+                @test collect(diagview(S1)) ≈ collect(diagview(S)[1:3])
+
+                # trunctol(rtol=0.2) keeps 2 values, truncrank(1) keeps 1, union keeps 2
+                U2, S2, V2ᴴ, ϵ2 = svd_trunc(A; trunc = trunc_fun(0.2, 1), alg)
+                @test length(diagview(S2)) == 2
+                @test collect(diagview(S2)) ≈ collect(diagview(S)[1:2])
+            end
+        end
         @testset "specify truncation algorithm" begin
             atol = sqrt(eps(real(eltype(T))))
             m4 = 4

test/truncate.jl

@@ -1,8 +1,8 @@
 using MatrixAlgebraKit
 using Test
 using TestExtras
-using MatrixAlgebraKit: NoTruncation, TruncationIntersection, TruncationByOrder,
-    TruncationByValue, TruncationStrategy, findtruncated, findtruncated_svd
+using MatrixAlgebraKit: NoTruncation, TruncationIntersection, TruncationUnion,
+    TruncationByOrder, TruncationByValue, TruncationStrategy, findtruncated, findtruncated_svd
 
 @testset "truncate" begin
     trunc = @constinferred TruncationStrategy()
@@ -65,4 +65,32 @@ using MatrixAlgebraKit: NoTruncation, TruncationIntersection, TruncationByOrder,
     @test issetequal(values[@constinferred(findtruncated(values, strategy))], values[2:5])
     vals_sorted = sort(values; by = abs, rev = true)
     @test vals_sorted[@constinferred(findtruncated_svd(vals_sorted, strategy))] == vals_sorted[1:4]
+
+    # TruncationUnion / minrank
+    trunc = @constinferred TruncationStrategy(; minrank = 3)
+    @test trunc isa TruncationByOrder
+    @test trunc == truncrank(3)
+
+    trunc = @constinferred TruncationStrategy(; atol, minrank = 3)
+    @test trunc isa TruncationUnion
+    @test trunc == trunctol(; atol) | truncrank(3)
+
+    # | operator
+    values2 = [1.0, 0.9, 0.5, 0.3, 0.01]
+    # trunctol keeps 1:3 (above 0.4), truncrank(4) keeps 1:4, union keeps 1:4
+    strategy = trunctol(; atol = 0.4) | truncrank(4)
+    @test @constinferred(findtruncated_svd(values2, strategy)) == 1:4
+    # trunctol keeps 1:3, truncrank(2) keeps 1:2, union keeps 1:3
+    strategy = trunctol(; atol = 0.4) | truncrank(2)
+    @test @constinferred(findtruncated_svd(values2, strategy)) == 1:3
+
+    # notrunc is absorbing for |
+    @test (notrunc() | truncrank(3)) isa NoTruncation
+    @test (truncrank(3) | notrunc()) isa NoTruncation
+
+    # TruncationUnion flattening
+    union1 = truncrank(2) | trunctol(; atol = 0.4)
+    union2 = union1 | truncrank(4)
+    @test union2 isa TruncationUnion
+    @test length(union2.components) == 3
 end