Repair flattenings of graded modules

.github/workflows/CI.yml

@@ -52,12 +52,14 @@ jobs:
           - julia-version: '1.10'
             group: 'long'
             os: macOS-latest
-          - julia-version: 'nightly'
-            group: 'short'
-            os: macOS-latest
-          - julia-version: 'nightly'
-            group: 'long'
-            os: macOS-latest
+          # nightly on macos is disabled for now since the macos jobs take too long
+          # with just 5 runners
+          #- julia-version: 'nightly'
+          #  group: 'short'
+          #  os: macOS-latest
+          #- julia-version: 'nightly'
+          #  group: 'long'
+          #  os: macOS-latest
 
     steps:
       - uses: actions/checkout@v3

Project.toml

@@ -30,7 +30,7 @@ AbstractAlgebra = "0.35.2"
 AlgebraicSolving = "0.4.6"
 Distributed = "1.6"
 DocStringExtensions = "0.8, 0.9"
-GAP = "0.10.0"
+GAP = "0.10.2"
 Hecke = "0.24.0"
 JSON = "^0.20, ^0.21"
 JSON3 = "1.13.2"

docs/doc.main

@@ -213,6 +213,18 @@
      ]
   ],
 
+  "Tropical Geometry" => [
+     "TropicalGeometry/intro.md",
+     "TropicalGeometry/semiring.md",
+     "TropicalGeometry/semiring_map.md",
+     "TropicalGeometry/variety.md",
+     "TropicalGeometry/hypersurface.md",
+     "TropicalGeometry/curve.md",
+     "TropicalGeometry/linear_space.md",
+     "TropicalGeometry/groebner_theory.md",
+     "TropicalGeometry/tropicalization.md",
+  ],
+
  "Noncommutative Algebra" => [
     "NoncommutativeAlgebra/intro.md",
     "PBW-Algebras" => [
@@ -239,20 +251,6 @@
       "StraightLinePrograms/abstractalgebra.md",
    ],
 
-
-  "Tropical Geometry" => [
-     "TropicalGeometry/intro.md",
-     "TropicalGeometry/semiring.md",
-     "TropicalGeometry/semiring_map.md",
-     "TropicalGeometry/variety.md",
-     "TropicalGeometry/hypersurface.md",
-     "TropicalGeometry/curve.md",
-     "TropicalGeometry/linear_space.md",
-     "TropicalGeometry/groebner_theory.md",
-     "TropicalGeometry/tropicalization.md",
-  ],
-
-
   "References" => "references.md",
   "Index" => "manualindex.md",
   "Developer Documentation" => [

docs/oscar_references.bib

@@ -1785,6 +1785,18 @@ @Misc{Stacks
   url           = {https://stacks.math.columbia.edu/}
 }
 
+@InCollection{Ste01,
+  author        = {Stembridge, John R.},
+  title         = {Computational aspects of root systems, {C}oxeter groups, and {W}eyl characters},
+  booktitle     = {Interaction of combinatorics and representation theory},
+  series        = {MSJ Memoirs},
+  volume        = {11},
+  publisher     = {The Mathematical Society of Japan},
+  pages         = {1--38},
+  year          = {2001},
+  doi           = {10.2969/msjmemoirs/01101C010}
+}
+
 @InCollection{Ste91,
   author        = {Stevens, Jan},
   title         = {On the versal deformation of cyclic quotient singularities},

docs/src/CommutativeAlgebra/ModulesOverMultivariateRings/free_modules.md

@@ -174,7 +174,7 @@ is_homogeneous(f::FreeModElem)
 ```
 
 ```@docs
-degree(f::FreeModElem)
+    degree(f::FreeModElem{T}) where {T<:Union{<:MPolyDecRingElem, <:MPolyQuoRingElem{<:MPolyDecRingElem}}}
 ```
 
 

docs/src/DeveloperDocumentation/printing_details.md

@@ -187,18 +187,18 @@ struct A{T}
 end
 
 function Base.show(io::IO, a::A)
-  io = AbstractAlgebra.pretty(io)
+  io = pretty(io)
   println(io, "Something of type A")
-  print(io, AbstractAlgebra.Indent(), "over ", AbstractAlgebra.Lowercase(), a.x)
-  print(io, AbstractAlgebra.Dedent()) # don't forget to undo the indentation!
+  print(io, Indent(), "over ", Lowercase(), a.x)
+  print(io, Dedent()) # don't forget to undo the indentation!
 end
 
 struct B
 end
 
 function Base.show(io::IO, b::B)
-  io = AbstractAlgebra.pretty(io)
-  print(io, AbstractAlgebra.LowercaseOff(), "Hilbert thing")
+  io = pretty(io)
+  print(io, LowercaseOff(), "Hilbert thing")
 end
 ```
 
@@ -233,7 +233,7 @@ julia> struct C{T}
 julia> function Base.show(io::IO, c::C{T}) where T
        x = c.x
        n = length(x)
-       print(io, "Something with ", AbstractAlgebra.ItemQuantity(n, "element"), " of type $T")
+       print(io, "Something with ", ItemQuantity(n, "element"), " of type $T")
        end
 ```
 

docs/src/General/faq.md

@@ -114,9 +114,20 @@ even if `zero(typeof(elm))` may not.
 
 ---
 
-**Q: How can I install or access custom GAP packages (e.g. unpublished ones)?**
+**Q: How can I access or install custom GAP packages (e.g. unpublished ones)?**
 
-TODO
+An already locally installed GAP package can be loaded into the OSCAR session
+via `GAP.Packages.load`, where the first argument is the local path to the
+package directory (the one that contains the `PackageInfo.g` file).
+This works only if no other version of this package has been loaded already.
+
+If Oscar loads the package in question already on startup
+but you want a different version of this package to be loaded,
+you can force this by storing the desired version in the `pkg` subdirectory
+of the user's root directory (`GAPInfo.UserGapRoot` in GAP).
+
+Installing a new GAP package for which you know the URL of a package archive
+can be done via `GAP.Packages.install`, where the first argument is this URL.
 
 ---
 

experimental/DoubleAndHyperComplexes/src/Morphisms/simplified_complexes.jl

@@ -587,3 +587,86 @@ function _has_index(a::SMat, i::Int, j::Int)
   return _has_index(a[i], j)
 end
 
+### Taylormade functionality for modules
+# Provided as a hotfix for issue #3108.
+function _alt_simplify(M::SubquoModule)
+  res, aug = free_resolution(SimpleFreeResolution, M)
+  simp = simplify(res)
+  simp_to_orig = map_to_original_complex(simp)
+  orig_to_simp = map_from_original_complex(simp)
+  result, Z0_to_result = homology(simp, 0)
+  Z0, inc_Z0 = kernel(simp, 0)
+
+  result_to_M = hom(result, M, 
+                    elem_type(M)[aug[0](simp_to_orig[0](inc_Z0(preimage(Z0_to_result, x)))) for x in gens(result)])
+  M_to_result = hom(M, result,
+                    elem_type(result)[Z0_to_result(preimage(inc_Z0, orig_to_simp[0](preimage(aug[0], y)))) for y in gens(M)])
+  return result, M_to_result, result_to_M
+end
+
+# Some special shortcuts
+function boundary(c::SimplifiedComplex{ChainType}, p::Int, i::Tuple) where {ChainType<:ModuleFP}
+  # try to find the boundary already computed
+  und = underlying_complex(c)::HyperComplex
+  if !isdefined(und, :boundary_cache) 
+    und.boundary_cache = Dict{Tuple{Tuple, Int}, Map}()
+  end
+  if haskey(und.boundary_cache, (i, p))
+    inc = und.boundary_cache[(i, p)]
+    return domain(inc), inc
+  end
+
+  # compute the boundary from scratch
+  orig_boundary, orig_inc = boundary(c.original_complex, p, i)
+  from_orig = map_from_original_complex(c)[i]
+  result, inc = sub(c[i], from_orig.(orig_inc.(gens(orig_boundary))))
+
+  # Cache the result
+  und.boundary_cache[(i, p)] = inc
+
+  return result, inc
+end
+
+function kernel(simp::SimplifiedComplex{ChainType}, p::Int, i::Tuple) where {ChainType<:ModuleFP}
+  c = underlying_complex(simp)::HyperComplex
+
+  if !isdefined(c, :kernel_cache) 
+    c.kernel_cache = Dict{Tuple{Tuple, Int}, Map}()
+  end
+  if haskey(c.kernel_cache, (i, p))
+    inc = c.kernel_cache[(i, p)]
+    return domain(inc), inc
+  end
+
+  if !can_compute_map(simp, p, i)
+    M = simp[i]
+    K, inc = sub(simp[i], gens(simp[i]))
+    c.kernel_cache[(i, p)] = inc
+    return K, inc
+  end
+
+  psi = map_to_original_complex(simp)[i]
+  orig = simp.original_complex # TODO: Use getter!
+  phi = map(orig, p, i)
+  K, inc = kernel(compose(psi, phi))
+  c.kernel_cache[(i, p)] = inc
+  return K, inc
+end
+
+function homology(simp::SimplifiedComplex{ChainType}, p::Int, i::Tuple) where {ChainType <: ModuleFP}
+  c = underlying_complex(simp)::HyperComplex
+
+  if !isdefined(c, :homology_cache) 
+    c.homology_cache = Dict{Tuple{Tuple, Int}, Map}()
+  end
+  if haskey(c.homology_cache, (i, p))
+    pr = c.homology_cache[(i, p)]
+    return codomain(pr), pr
+  end
+
+  H, pr = quo(kernel(simp, p, i)[1], boundary(simp, p, i)[1])
+  c.homology_cache[(i, p)] = pr
+  return H, pr
+end
+
+homology(simp::SimplifiedComplex{ChainType}, i::Int) where {ChainType <: ModuleFP} = homology(simp, 1, (i,))

experimental/DoubleAndHyperComplexes/src/Objects/tor.jl

@@ -5,17 +5,29 @@ end
 
 function homology(hc::AbsHyperComplex, i::Int)
   dim(hc) == 1 || error("dimension of the hypercomplex must be one")
-  return homology(underlying_complex(hc), 1, (i,))
+  return homology(hc, 1, (i,))
 end
 
 function kernel(hc::AbsHyperComplex, i::Int)
   dim(hc) == 1 || error("dimension of the hypercomplex must be one")
-  return kernel(underlying_complex(hc), 1, (i,))
+  return kernel(hc, 1, (i,))
 end
 
 function boundary(hc::AbsHyperComplex, i::Int)
   dim(hc) == 1 || error("dimension of the hypercomplex must be one")
-  return boundary(underlying_complex(hc), 1, (i,))
+  return boundary(hc, 1, (i,))
+end
+
+function homology(hc::AbsHyperComplex, p::Int, i::Tuple)
+  return homology(underlying_complex(hc), p, i)
+end
+
+function kernel(hc::AbsHyperComplex, p::Int, i::Tuple)
+  return kernel(underlying_complex(hc), p, i)
+end
+
+function boundary(hc::AbsHyperComplex, p::Int, i::Tuple)
+  return boundary(underlying_complex(hc), p, i)
 end
 
 function tor(M1::ModuleFP{T}, M2::ModuleFP{T}, i::Int) where {U<:MPolyComplementOfPrimeIdeal, T<:MPolyLocRingElem{<:Any, <:Any, <:Any, <:Any, U}}

experimental/GModule/Cohomology.jl

@@ -8,6 +8,8 @@ import Oscar: GAPWrap, pc_group, fp_group, direct_product, direct_sum
 import AbstractAlgebra: Group, Module
 import Base: parent
 
+import Oscar: pretty, Lowercase, @show_name, @show_special
+
 function __init__()
   Hecke.add_verbose_scope(:GroupCohomology)
   Hecke.add_assert_scope(:GroupCohomology)
@@ -104,11 +106,12 @@ Base.hash(a::MultGrpElem, u::UInt = UInt(1235)) = hash(a.data. u)
 end
 
 function Base.show(io::IO, C::GModule)
-  AbstractAlgebra.@show_name(io, C)
-  AbstractAlgebra.@show_special(io, C)
+  @show_name(io, C)
+  @show_special(io, C)
 
+  io = pretty(io)
   io = IOContext(io, :compact => true)
-  print(io, "G-module for ", C.G, " acting on ", C.M)# , "\nvia: ", C.ac)
+  print(io, "G-module for ", Lowercase(), C.G, " acting on ", Lowercase(), C.M)# , "\nvia: ", C.ac)
 end
 
 """