Merge pull request #3910 from oscar-system/backports-release-1.1

Project.toml

@@ -1,7 +1,7 @@
 name = "Oscar"
 uuid = "f1435218-dba5-11e9-1e4d-f1a5fab5fc13"
 authors = ["The OSCAR Team <[email protected]>"]
-version = "1.1.0"
+version = "1.1.1"
 
 [deps]
 AbstractAlgebra = "c3fe647b-3220-5bb0-a1ea-a7954cac585d"

README.md

@@ -37,7 +37,7 @@ julia> using Oscar
  / _ \ / ___| / ___|  / \  |  _ \   |  Combining ANTIC, GAP, Polymake, Singular
 | | | |\___ \| |     / _ \ | |_) |  |  Type "?Oscar" for more information
 | |_| | ___) | |___ / ___ \|  _ <   |  Manual: https://docs.oscar-system.org
- \___/ |____/ \____/_/   \_\_| \_\  |  Version 1.1.0
+ \___/ |____/ \____/_/   \_\_| \_\  |  Version 1.1.1
 julia> k, a = quadratic_field(-5)
 (Imaginary quadratic field defined by x^2 + 5, sqrt(-5))
 
@@ -119,7 +119,7 @@ pm::Array<topaz::HomologyGroup<pm::Integer> >
 If you have used OSCAR in the preparation of a paper please cite it as described below:
 
     [OSCAR]
-        OSCAR -- Open Source Computer Algebra Research system, Version 1.1.0,
+        OSCAR -- Open Source Computer Algebra Research system, Version 1.1.1,
         The OSCAR Team, 2024. (https://www.oscar-system.org)
     [OSCAR-book]
         Wolfram Decker, Christian Eder, Claus Fieker, Max Horn, Michael Joswig, eds.
@@ -132,7 +132,7 @@ If you are using BibTeX, you can use the following BibTeX entries:
       key          = {OSCAR},
       organization = {The OSCAR Team},
       title        = {OSCAR -- Open Source Computer Algebra Research system,
-                      Version 1.1.0},
+                      Version 1.1.1},
       year         = {2024},
       url          = {https://www.oscar-system.org},
       }

etc/update_version.sh

@@ -28,7 +28,7 @@ echo "Setting version to $relvers, released $reldate_iso"
 
 # update version in several files
 perl -pi -e 's;version = "[^"]+";version = "'$relvers'";' Project.toml
-perl -pi -e "s;Version [^ },]+;Version $relvers;" README.md
+perl -pi -e "s;Version [^\s},]+;Version $relvers;" README.md
 perl -pi -e 's;Date := "[^"]+",;Date := "'$reldate'",;' gap/OscarInterface/PackageInfo.g
 perl -pi -e 's;Version := "[^"]+",;Version := "'$relvers'",;' gap/OscarInterface/PackageInfo.g
 

experimental/Schemes/src/IdealSheaves.jl

@@ -869,7 +869,8 @@ function maximal_associated_points(
     I::AbsIdealSheaf; 
     covering=default_covering(scheme(I)), 
     use_decomposition_info::Bool=true,
-    algorithm::Symbol=:GTZ
+    algorithm::Symbol=:GTZ,
+    mode::Symbol=:save_gluings
   )
   X = scheme(I)
   comps = AbsIdealSheaf[]
@@ -899,8 +900,27 @@ function maximal_associated_points(
     end
   end
 
+  if mode==:save_gluings && length(comps)==1
+    R = radical(I)
+    set_attribute!(R, :is_prime=>true)
+    P = comps[1]
+    U = original_chart(P)
+    object_cache(R)[U] = P(U)
+    comps = AbsIdealSheaf[R]
+  end
   # Manually fill up the cache
-  if !use_decomposition_info # We can only do this if all we treated all components on all charts.
+  if use_decomposition_info 
+    # we can at least remember some partial information 
+    for U in patches(covering)
+      if isone(I(U))
+        I_one = ideal(OO(U), one(OO(U)))
+        for P in comps
+          object_cache(P)[U] = I_one
+        end
+      end
+    end
+  else 
+    # We can only do this if all we treated all components on all charts.
     for U in patches(covering)
       I_one = ideal(OO(U), one(OO(U)))
       for P in comps
@@ -1390,6 +1410,7 @@ function saturation(I::AbsIdealSheaf, J::AbsIdealSheaf)
 end
 
 function pushforward(f::AbsCoveredSchemeMorphism, II::AbsIdealSheaf)
+  @req domain(f)===space(II) "ideal sheaf not defined on domain of morphism"
   f_cov = covering_morphism(f)
   dom_cov = domain(f_cov)
   cod_cov = codomain(f_cov)
@@ -1401,6 +1422,7 @@ function pushforward(f::AbsCoveredSchemeMorphism, II::AbsIdealSheaf)
   end
   return IdealSheaf(codomain(f), ideal_dict, check=true) #TODO: Set to false
 end
+
 
 function Base.:^(II::AbsIdealSheaf, k::IntegerUnion)
   k < 0 && error("negative powers of ideal sheaves are not allowed")
@@ -1933,7 +1955,7 @@ function is_subset(I::PrimeIdealSheafFromChart, rad::RadicalOfIdealSheaf)
   U = original_chart(I)
   return all(g->radical_membership(g, rad(U)), gens(I(U)))
 end
-
+ 
 function radical(I::AbsIdealSheaf)
   result = RadicalOfIdealSheaf(I)
   return result
@@ -1944,6 +1966,13 @@ is_radical(rad::RadicalOfIdealSheaf) = true
 ########################################################################
 # custom functionality for prime ideal sheaves from chart
 ########################################################################
+function is_subset(I::AbsIdealSheaf, P::PrimeIdealSheafFromChart)
+  X = scheme(I)
+  @assert X === scheme(P)
+  U = original_chart(P)
+  return is_subset(I(U), P(U))
+end
+
 
 function is_subset(P::PrimeIdealSheafFromChart, I::AbsIdealSheaf)
   X = scheme(P)

experimental/Schemes/src/elliptic_surface.jl

@@ -948,15 +948,46 @@ end
 
 Return the fiber components of the fiber over the point $P \in C$.
 """
-function fiber_components(S::EllipticSurface, P)
+function fiber_components(S::EllipticSurface, P; algorithm=:exceptional_divisors)
   @vprint :EllipticSurface 2 "computing fiber components over $(P)\n"
-  F = fiber_cartier(S, P)
-  @vprint :EllipticSurface 2 "decomposing fiber   "
-  comp = maximal_associated_points(ideal_sheaf(F))
-  @vprint :EllipticSurface 2 "done decomposing fiber\n"
-  return [weil_divisor(c, check=false) for c in comp]
+  P = base_ring(S).(P)
+  W = codomain(S.inc_Weierstrass)
+  Fcart = fiber_cartier(S, P)
+  if isone(P[2])
+    U = default_covering(W)[1]
+    (x,y,t) = coordinates(U)
+    F = PrimeIdealSheafFromChart(W, U, ideal(t - P[1]))
+  elseif isone(P[1])
+    U = default_covering(W)[4]
+    (x,y,s) = coordinates(U)
+    F = PrimeIdealSheafFromChart(W, U, ideal(s - P[2]))
+  end 
+  FF = ideal_sheaf(Fcart)
+  EE = exceptional_divisors(S)
+  EP = filter(E->issubset(FF, E), EE)
+  for bl in S.ambient_blowups
+    F = strict_transform(bl, F)
+  end
+  F = pullback(S.inc_Y, F)
+  F = weil_divisor(F, ZZ)
+  fiber_components = [weil_divisor(E, ZZ) for E in EP]
+  push!(fiber_components, F)
+  return fiber_components
 end
-
+
+@attr function exceptional_divisors(S::EllipticSurface)
+  PP = AbsIdealSheaf[]
+  @vprintln :EllipticSurface 2 "computing exceptional divisors"
+  for E in S.ambient_exceptionals
+    @vprintln :EllipticSurface 4 "decomposing divisor "
+    mp = maximal_associated_points(ideal_sheaf(pullback(S.inc_Y,E));
+                                   use_decomposition_info=true)
+    append!(PP, mp)
+  end 
+  @vprintln :EllipticSurface 3 "done"
+  return PP
+end
+
 function fiber(X::EllipticSurface)
   b, pt, F = irreducible_fiber(X)
   if b
@@ -1589,12 +1620,12 @@ degree at most ``4`` to Weierstrass form, apply Tate's algorithm and
 return the corresponding relatively minimal elliptic surface 
 as well as the coordinate transformation.
 """
-function elliptic_surface(g::MPolyRingElem, P::Vector{<:RingElem})
+function elliptic_surface(g::MPolyRingElem, P::Vector{<:RingElem}; minimize=true)
   R = parent(g)
   (x, y) = gens(R)
   P = base_ring(R).(P)
   g2, phi2 = transform_to_weierstrass(g, x, y, P);
-  Y2, phi1 = _elliptic_surface_with_trafo(g2)
+  Y2, phi1 = _elliptic_surface_with_trafo(g2; minimize)
   return Y2, phi2 * phi1  
 end
 
@@ -1628,6 +1659,7 @@ function transform_to_weierstrass(g::MPolyRingElem, x::MPolyRingElem, y::MPolyRi
     return switch(g_trans), new_trans
   end
 
+  g = inv(coeff(g,[0,2]))*g # normalise g
   kk = coefficient_ring(R)
   kkx, X = polynomial_ring(kk, :x, cached=false)
   kkxy, Y = polynomial_ring(kkx, :y, cached=false)
@@ -1640,11 +1672,19 @@ function transform_to_weierstrass(g::MPolyRingElem, x::MPolyRingElem, y::MPolyRi
   @assert all(h->degree(h)<=4, coefficients(G)) "input polynomial must be of degree <= 4 in x"
   @assert iszero(coefficients(G)[1]) "coefficient of linear term in y must be zero"
   @assert isone(coefficients(G)[2]) "leading coefficient in y must be one"
+
+  if length(P) == 3 && isone(P[3])
+      P = P[1:2]
+  end 
+
 
-  length(P) == 2 || error("need precisely two point coordinates")
-  (px, py) = P
+  if length(P) == 2
+    @assert iszero(evaluate(g, P)) "point does not lie on the hypersurface"
+    (px, py) = P
+  else 
+    px = P[1]
+  end
   #    assert g.subs({x:px,y:py})==0
-  @assert iszero(evaluate(g, P)) "point does not lie on the hypersurface"
   gx = -evaluate(g, [X + px, zero(X)])
   coeff_gx = collect(coefficients(gx))
   A = coeff(gx, 4)
@@ -1653,7 +1693,16 @@ function transform_to_weierstrass(g::MPolyRingElem, x::MPolyRingElem, y::MPolyRi
   D = coeff(gx, 1)
   E = coeff(gx, 0)
   #E, D, C, B, A = coeff_gx
-  if !iszero(E)
+  if length(P)==3
+    @req all(h->degree(h)<=3, coefficients(G)) "infinity (0:1:0) is not a point of this hypersurface"
+    # y^2 = B*x^3+C*x^2+C*x+D
+    x1 = F(inv(B)*x)
+    y1 = F(inv(B)*y)
+    trans = MapFromFunc(F, F, f->evaluate(numerator(f), [x1, y1])//evaluate(denominator(f), [x1, y1]))
+    f_trans = B^2*trans(F(g))
+    result = numerator(B^2*f_trans)
+    return result, trans
+  elseif !iszero(E)
     b = py
     a4, a3, a2, a1, a0 = A,B,C,D,E
     A = b
@@ -2286,7 +2335,7 @@ end
 # The transformation is a morphism from the fraction field of the 
 # parent of g to the fraction field of the `ambient_coordinate_ring` 
 # of the `weierstrass_chart` of the resulting surface.
-function _elliptic_surface_with_trafo(g::MPolyRingElem{<:AbstractAlgebra.Generic.FracFieldElem})
+function _elliptic_surface_with_trafo(g::MPolyRingElem{<:AbstractAlgebra.Generic.FracFieldElem}; minimize::Bool=true)
   x, y = gens(parent(g))
   E = elliptic_curve(g, x, y)
   kkt = base_field(E)
@@ -2296,11 +2345,12 @@ function _elliptic_surface_with_trafo(g::MPolyRingElem{<:AbstractAlgebra.Generic
 
   # The following three commands won't work unless we convert to a rational_function_field
   EE = base_change(x->evaluate(x, t), E)
-
-  EE = tates_algorithm_global(EE)
-  EE, _ = short_weierstrass_model(EE)
-  EE, _ = integral_model(EE)
-
+  if minimize
+    EE = tates_algorithm_global(EE)
+    EE, _ = short_weierstrass_model(EE)
+    EE, _ = integral_model(EE)
+  end
+
   # ...and back.
   E2 = base_change(x->evaluate(x, gen(kkt)), EE)
 

gap/OscarInterface/PackageInfo.g

@@ -10,8 +10,8 @@ SetPackageInfo( rec(
 
 PackageName := "OscarInterface",
 Subtitle := "GAP interface to OSCAR",
-Version := "1.1.0",
-Date := "20/06/2024", # dd/mm/yyyy format
+Version := "1.1.1",
+Date := "03/07/2024", # dd/mm/yyyy format
 License := "GPL-2.0-or-later",
 
 Persons := [

test/AlgebraicGeometry/Schemes/elliptic_surface.jl

@@ -1,9 +1,4 @@
-# The tests for elliptic surfaces have lead to random failure of the CI-tests, 
-# see issue no. 3676. 
-#
-# They are now disabled, also because in general they tend to take quite long.
-# We keep them, however, to allow for running them locally.
-#=
+
 @testset "elliptic surfaces" begin
   @testset "trivial lattice" begin
     k = GF(29)
@@ -27,9 +22,18 @@
     X = elliptic_surface(E, 2)
     triv = trivial_lattice(X)
     @test det(triv[2])==-3
+  end
+
+  @testset "trivial lattice QQ" begin
+    Qt, t = polynomial_ring(QQ, :t)
+    Qtf = fraction_field(Qt)
+    E = elliptic_curve(Qtf, [0,0,0,0,t^5*(t-1)^2])
+    X3 = elliptic_surface(E, 2)
+    weierstrass_contraction(X3)
+    trivial_lattice(X3)
   end  
 
-  # This test takes about 1 minute
+  # This test takes about 30 seconds
   @testset "mordel weil lattices" begin
     k = GF(29,2)
     # The generic fiber of the elliptic fibration
@@ -51,17 +55,9 @@
     X1 = elliptic_surface(short_weierstrass_model(E)[1],2)
     Oscar.isomorphism_from_generic_fibers(X,X1)
   end
-  #=
-  # this test is quite expensive
-  # probably because it is over QQ
-  # ... and because there are loads of complicated singular fibers
-  Qt, t = polynomial_ring(QQ, :t)
-  Qtf = fraction_field(Qt)
-  E = elliptic_curve(Qtf, [0,0,0,0,t^5*(t-1)^2])
-  X3 = elliptic_surface(E, 2)
-  weierstrass_contraction(X3)
-  trivial_lattice(X3)
-  =#
+
+
+
 
   @testset "elliptic parameter" begin
     k = GF(29)
@@ -126,8 +122,7 @@ end
 
 
 #=
-# These tests are disabled, because they take too long, about 5 minutes. But one can run them if in doubt.
-# most of the time is spent in decomposing the fibers
+# These tests are disabled, because they are dependent on factorisation order...
 @testset "two neighbor steps" begin
   K = GF(7)
   Kt, t = polynomial_ring(K, :t)
@@ -188,9 +183,9 @@ end
   # The following should not take more than at most two minutes.
   # But it broke the tests at some point leading to timeout, 
   # so we put it here to indicate regression.
-  for (i, g) in enumerate(values(gluings(default_covering(X))))
-    gluing_domains(g) # Trigger the computation once
-  end
+  #for (i, g) in enumerate(values(gluings(default_covering(X))))
+  #  gluing_domains(g) # Trigger the computation once
+  #end
 
   D_P = section(X, P)
  
@@ -272,4 +267,4 @@ end
   P = Oscar.extract_mordell_weil_basis(torsion_translation)
   @test length(P) == 2
 end
-=#
+