From 6c72843e899e87a0a574aaaa1f3031ecedc21cee Mon Sep 17 00:00:00 2001
From: Johannes Schmitt <schmitt@mathematik.uni-kl.de>
Date: Wed, 24 Jan 2024 13:16:57 +0100
Subject: [PATCH] Remove eigenvalues and eigenspaces (now in Nemo)

---
 src/Misc/jordan.jl       | 75 ----------------------------------------
 src/exports.jl           |  3 --
 test/Misc/jordan_test.jl | 38 +-------------------
 3 files changed, 1 insertion(+), 115 deletions(-)

diff --git a/src/Misc/jordan.jl b/src/Misc/jordan.jl
index dc2af265f6..20306f4ea8 100644
--- a/src/Misc/jordan.jl
+++ b/src/Misc/jordan.jl
@@ -1,78 +1,3 @@
-@doc raw"""
-    spectrum(M::MatElem{T}) where T <: FieldElem -> Dict{T, Int}
-
-Returns the spectrum of a matrix, i.e. the set of eigenvalues of $M$ with multiplicities.
-"""
-function spectrum(M::MatElem{T}) where T <: FieldElem
-  @assert is_square(M)
-  K = base_ring(M)
-  f = charpoly(M)
-  fac = factor(f) #Should use roots! But needs to take into account
-                  #multiplicities
-  D = Dict{elem_type(K), Int}()
-  for (g, v) in fac
-    if degree(g) > 1
-      continue
-    end
-    lambda = -divexact(coeff(g, 0), leading_coefficient(g))
-    D[lambda] = v
-  end
-  return D
-end
-
-@doc raw"""
-    spectrum(M::MatElem{T}, L) where T <: FieldElem -> Dict{T, Int}
-
-Returns the spectrum of a matrix over the field $L$, i.e. the set of eigenvalues of $M$ with multiplicities.
-"""
-function spectrum(M::MatElem{T}, L) where T <: FieldElem
-  @assert is_square(M)
-  M1 = change_base_ring(L, M)
-  return spectrum(M1)
-end
-
-eigvals(M::MatElem{T}) where T <: FieldElem = spectrum(M)
-eigvals(M::MatElem{T}, L) where T <: FieldElem = spectrum(M, L)
-
-@doc raw"""
-    eigenspace(M::MatElem{T}, lambda::T; side::Symbol = :right)
-      where T <: FieldElem -> Vector{MatElem{T}}
-
-Return a basis of the eigenspace of $M$ with respect to the eigenvalue $\lambda$.
-If side is `:right`, the right eigenspace is computed, i.e. vectors $v$ such that
-$Mv = \lambda v$. If side is `:left`, the left eigenspace is computed, i.e. vectors
-$v$ such that $vM = \lambda v$.
-"""
-function eigenspace(M::MatElem{T}, lambda::T; side::Symbol = :right) where T <: FieldElem
-  @assert is_square(M)
-  N = deepcopy(M)
-  for i = 1:ncols(N)
-    N[i, i] -= lambda
-  end
-  return kernel(N, side = side)[2]
-end
-
-@doc raw"""
-    eigenspace(M::MatElem{T}; side::Symbol = :right)
-      where T <: FieldElem -> Dict{T, MatElem{T}}
-
-Return a dictionary containing the eigenvalues of $M$ as keys and bases for the
-corresponding eigenspaces as values.
-If side is `:right`, the right eigenspaces are computed, if it is `:left` then the
-left eigenspaces are computed.
-
-See also `eigenspace`.
-"""
-function eigenspaces(M::MatElem{T}; side::Symbol = :right) where T<:Hecke.FieldElem
-
-  S = spectrum(M)
-  L = Dict{elem_type(base_ring(M)), typeof(M)}()
-  for k in keys(S)
-    push!(L, k => Hecke.vcat(Hecke.eigenspace(M, k, side = side)))
-  end
-  return L
-end
-
 function closure_with_pol(v::MatElem{T}, M::MatElem{T}) where T <: FieldElem
   i = 1
   E = rref(v)[2]
diff --git a/src/exports.jl b/src/exports.jl
index 75c7c24506..e7725e4d4c 100644
--- a/src/exports.jl
+++ b/src/exports.jl
@@ -306,8 +306,6 @@ export dual_isogeny
 export dual_of_frobenius
 export echelon_with_transform
 export ei
-export eigenspace
-export eigenspaces
 export eisenstein_extension
 export elem_in_algebra
 export elem_in_nf
@@ -881,7 +879,6 @@ export sparse_trafo_partial_dense
 export sparse_trafo_scale
 export sparse_trafo_swap
 export sparsity
-export spectrum
 export splitting_field
 export sqrt
 export stabilizer
diff --git a/test/Misc/jordan_test.jl b/test/Misc/jordan_test.jl
index 92e1b2007b..87c51b5f6b 100644
--- a/test/Misc/jordan_test.jl
+++ b/test/Misc/jordan_test.jl
@@ -59,44 +59,8 @@
   @test Set([ J[1, 1], J[2, 2], J[3, 3] ]) == Set([ K(), K(1), K(-1) ])
 end
 
-@testset "Spectrum and eigenspaces" begin
-  M = matrix(FlintQQ, 4, 4, [ 0, 0, 1, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1 ])
-  l = eigvals(M)
-  @test length(keys(l)) == 1
-  @test haskey(l, one(FlintQQ))
-  @test l[one(FlintQQ)] == 2
-
+@testset "Common eigenspaces" begin
   K, a = cyclotomic_field(3, "a")
-  lK = eigvals(M, K)
-  @test length(keys(lK)) == 3
-  @test haskey(lK, one(K)) && haskey(lK, a) && haskey(lK, -a - 1)
-  @test lK[one(K)] == 2
-  @test lK[a] == 1
-  @test lK[-a - 1] == 1
-
-  M = matrix(K, 4, 4, [ 0, 0, 1, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1 ])
-  lK2 = eigvals(M)
-  @test lK == lK2
-
-  Eig = eigenspaces(M, side = :right)
-  V = zero_matrix(K, 4, 0)
-  for (e, v) in Eig
-    @test haskey(lK2, e)
-    @test lK2[e] == ncols(v)
-    @test M*v == e*v
-    V = hcat(V, v)
-  end
-  @test rref!(V) == 4
-
-  Eig = eigenspaces(M, side = :left)
-  V = zero_matrix(K, 0, 4)
-  for (e, v) in Eig
-    @test haskey(lK2, e)
-    @test lK2[e] == nrows(v)
-    @test v*M == e*v
-    V = vcat(V, v)
-  end
-  @test rref!(V) == 4
 
   M = [ matrix(QQ, [ 0 1 0 0 0 0;
                     1 0 0 0 0 0;