From a028f2fd50e0f7eed63f2745d889f8677add47a3 Mon Sep 17 00:00:00 2001
From: lkdvos <lukas.devos@ugent.be>
Date: Mon, 1 Jan 2024 16:55:22 +0100
Subject: [PATCH] define `argmax(f, domain)` for julia < v1.7

---
 src/auxiliary/auxiliary.jl | 8 ++++++++
 src/auxiliary/linalg.jl    | 8 ++++----
 test/ad.jl                 | 2 +-
 3 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/src/auxiliary/auxiliary.jl b/src/auxiliary/auxiliary.jl
index f407f968..a00800a9 100644
--- a/src/auxiliary/auxiliary.jl
+++ b/src/auxiliary/auxiliary.jl
@@ -40,3 +40,11 @@ function _kron(A, B)
     end
     return C
 end
+
+# only defined in >v1.7
+@static if VERSION < v"1.7-"
+    _rf_findmax((fm, im), (fx, ix)) = isless(fm, fx) ? (fx, ix) : (fm, im)
+    _argmax(f, domain) = mapfoldl(x -> (f(x), x), _rf_findmax, domain)[2]
+else
+    _argmax = Base.argmax
+end
\ No newline at end of file
diff --git a/src/auxiliary/linalg.jl b/src/auxiliary/linalg.jl
index bc57d4c6..02cf503d 100644
--- a/src/auxiliary/linalg.jl
+++ b/src/auxiliary/linalg.jl
@@ -273,12 +273,12 @@ function eig!(A::StridedMatrix{T}; permute::Bool=true, scale::Bool=true) where {
     while j <= n
         if DI[j] == 0
             vr = view(VR, :, j)
-            s = conj(sign(argmax(abs, vr)))
+            s = conj(sign(_argmax(abs, vr)))
             V[:, j] .= s .* vr
         else
             vr = view(VR, :, j)
             vi = view(VR, :, j + 1)
-            s = conj(sign(argmax(abs, vr))) # vectors coming from lapack have already real absmax component
+            s = conj(sign(_argmax(abs, vr))) # vectors coming from lapack have already real absmax component
             V[:, j] .= s .* (vr .+ im .* vi)
             V[:, j + 1] .= s .* (vr .- im .* vi)
             j += 1
@@ -296,7 +296,7 @@ function eig!(A::StridedMatrix{T}; permute::Bool=true,
                          A)[[2, 4]]
     for j in 1:n
         v = view(V, :, j)
-        s = conj(sign(argmax(abs, v)))
+        s = conj(sign(_argmax(abs, v)))
         v .*= s
     end
     return D, V
@@ -308,7 +308,7 @@ function eigh!(A::StridedMatrix{T}) where {T<:BlasFloat}
     D, V = LAPACK.syevr!('V', 'A', 'U', A, 0.0, 0.0, 0, 0, -1.0)
     for j in 1:n
         v = view(V, :, j)
-        s = conj(sign(argmax(abs, v)))
+        s = conj(sign(_argmax(abs, v)))
         v .*= s
     end
     return D, V
diff --git a/test/ad.jl b/test/ad.jl
index 3b82c0b4..878031e5 100644
--- a/test/ad.jl
+++ b/test/ad.jl
@@ -312,7 +312,7 @@ Vlist = ((ℂ^2, (ℂ^3)', ℂ^3, ℂ^2, (ℂ^2)'),
             T <: Complex && remove_svdgauge_depence!(ΔU, ΔV, U, S, V)
             test_rrule(tsvd, C; atol, output_tangent=(ΔU, ΔS, ΔV, 0.0))
 
-            c, = argmax(x -> sqrt(dim(x[1])) * maximum(diag(x[2])), blocks(S))
+            c, = _argmax(x -> sqrt(dim(x[1])) * maximum(diag(x[2])), blocks(S))
             U, S, V, ϵ = tsvd(C; trunc=truncdim(2 * dim(c)))
             ΔU = TensorMap(randn, scalartype(U), space(U))
             ΔS = TensorMap(randn, scalartype(S), space(S))