Slightly refine gaussian_elimination semantics

Liozou · Jul 5, 2022 · 1e63355 · 1e63355
1 parent 2c54e06
commit 1e63355
Show file tree

Hide file tree

Showing 2 changed files with 31 additions and 23 deletions.
diff --git a/src/algorithms/rings.jl b/src/algorithms/rings.jl
@@ -1187,7 +1187,19 @@ end
 IterativeGaussianElimination(ring, sizehint=ring[1]) = IterativeGaussianEliminationNone(ring, sizehint)
 IterativeGaussianElimination() = IterativeGaussianEliminationNone()
 
-function _gaussian_elimination(gauss::IterativeGaussianElimination{T}, r::Vector{Int}) where T
+"""
+    gaussian_elimination(gauss::IterativeGaussianElimination, r::Vector{Int})
+
+Return `notindependent, info` where `notindependent` is `true` if `r` can be expressed as a
+sum of vectors stored in `gauss`.
+
+See [`PeriodicGraphs.gaussian_elimination!`](@ref) to store `r` in `gauss` if not, and for
+more details dependending on the type of `gauss`.
+
+Call `PeriodicGraphs.gaussian_elimination!(gauss, r, notindependent, info)` to obtain the
+result of `PeriodicGraphs.gaussian_elimination!(gauss, r)` without duplicating computation.
+"""
+function gaussian_elimination(gauss::IterativeGaussianElimination{T}, r::Vector{Int}) where T
     rings = gauss.rings
     shortcuts = gauss.shortcuts
     buffer1::Vector{Int} = gauss.buffer1
@@ -1212,7 +1224,7 @@ function _gaussian_elimination(gauss::IterativeGaussianElimination{T}, r::Vector
             push!(track, idx)
         end
         symdiff_cycles!(buffer1, r, ridx)
-        isempty(buffer1) && return true, r1, maxlen, buffer1
+        isempty(buffer1) && return true, (r1, maxlen, buffer1)
         r1 = buffer1[1]
         idx = r1 > lenshort ? zero(Int32) : shortcuts[r1]
     else
@@ -1226,24 +1238,15 @@ function _gaussian_elimination(gauss::IterativeGaussianElimination{T}, r::Vector
             push!(track, idx)
         end
         symdiff_cycles!(buffer2, buffer1, ridx)
-        isempty(buffer2) && return true, r1, maxlen, buffer1
+        isempty(buffer2) && return true, (r1, maxlen, buffer1)
         r1 = buffer2[1]
         idx = r1 > lenshort ? zero(Int32) : shortcuts[r1]
         buffer2, buffer1 = buffer1, buffer2
     end
 
-    return false, r1, maxlen, buffer1
+    return false, (r1, maxlen, buffer1)
 end
 
-"""
-    gaussian_elimination(gauss::IterativeGaussianElimination, r::Vector{Int})
-
-Test whether `r` can be expressed as a sum of vectors stored in `gauss`.
-
-See [`PeriodicGraphs.gaussian_elimination!`](@ref) to store `r` in `gauss` if not, and for
-more details dependending on the type of `gauss`.
-"""
-gaussian_elimination(gauss::IterativeGaussianElimination, r::Vector{Int}) = first(_gaussian_elimination(gauss, r))
 
 # For an IterativeGaussianElimination of i rings of size at most l, symdiff_cycles cost at
 # most (l + lenr) + (2l + lenr) + ... + (il + lenr) = O(i^2*l +i*lenr)
@@ -1267,6 +1270,11 @@ to obtain the sorted list of indices of such previously encountered vectors.
 See also [`gaussian_elimination`](@ref) to test `r` without storing it.
 """
 function gaussian_elimination!(gauss::IterativeGaussianElimination{T}, r::Vector{Int}) where T
+    notindependent, info = gaussian_elimination(gauss, r)
+    gaussian_elimination!(gauss, r, notindependent, info)
+end
+
+function gaussian_elimination!(gauss::IterativeGaussianElimination{T}, r::Vector{Int}, notindependent, (r1, maxlen, buffer1)) where T
     rings = gauss.rings
     shortcuts = gauss.shortcuts
     if gauss isa IterativeGaussianEliminationLength
@@ -1275,8 +1283,6 @@ function gaussian_elimination!(gauss::IterativeGaussianElimination{T}, r::Vector
         track::Vector{Int32} = first(gauss.track)
     end
 
-    notindependent, r1, maxlen, buffer1 = _gaussian_elimination(gauss, r)
-
     if notindependent
         gauss isa IterativeGaussianEliminationLength && return maxlen < len
         if gauss isa IterativeGaussianEliminationDecomposition

diff --git a/test/runtests.jl b/test/runtests.jl
@@ -742,12 +742,13 @@ end
     @test !PeriodicGraphs.gaussian_elimination!(gausslengths, [4, 7])
     @test !PeriodicGraphs.gaussian_elimination!(gausslengths, [1, 3, 5])
     @test length(gausslengths.track) == length(gausslengths.rings) == 4
-    @test PeriodicGraphs.gaussian_elimination(gausslengths, [1, 4, 5, 7])
+    @test first(PeriodicGraphs.gaussian_elimination(gausslengths, [1, 4, 5, 7]))
     @test PeriodicGraphs.gaussian_elimination!(gausslengths, [1, 4, 5, 7])
     @test length(gausslengths.track) == length(gausslengths.rings) == 4
     @test !PeriodicGraphs.gaussian_elimination!(gausslengths, [3, 5, 6, 7])
-    @test !PeriodicGraphs.gaussian_elimination(gausslengths, [2, 3])
-    @test !PeriodicGraphs.gaussian_elimination!(gausslengths, [2, 3])
+    notindependent, info = PeriodicGraphs.gaussian_elimination(gausslengths, [2, 3])
+    @test !notindependent
+    @test !PeriodicGraphs.gaussian_elimination!(gausslengths, [2, 3], notindependent, info)
     @test !PeriodicGraphs.gaussian_elimination!(gausslengths, [1, 2, 3])
     @test length(gausslengths.track) == length(gausslengths.rings) == 7
 
@@ -756,11 +757,11 @@ end
     @test !PeriodicGraphs.gaussian_elimination!(gaussnone, [4, 7])
     @test !PeriodicGraphs.gaussian_elimination!(gaussnone, [1, 3, 5])
     @test length(gaussnone.rings) == 4
-    @test PeriodicGraphs.gaussian_elimination(gaussnone, [1, 4, 5, 7])
+    @test first(PeriodicGraphs.gaussian_elimination(gaussnone, [1, 4, 5, 7]))
     @test PeriodicGraphs.gaussian_elimination!(gaussnone, [1, 4, 5, 7])
     @test !PeriodicGraphs.gaussian_elimination!(gaussnone, [3, 5, 6, 7])
     @test !PeriodicGraphs.gaussian_elimination!(gaussnone, [2, 3])
-    @test !PeriodicGraphs.gaussian_elimination(gaussnone, [1, 2, 3])
+    @test !first(PeriodicGraphs.gaussian_elimination(gaussnone, [1, 2, 3]))
     @test !PeriodicGraphs.gaussian_elimination!(gaussnone, [1, 2, 3])
     @test PeriodicGraphs.gaussian_elimination!(gaussnone, [1, 2, 3])
     @test gaussnone.shortcuts == Int32[4, 6, 1, 2, 5, 3, 7]
@@ -771,12 +772,13 @@ end
     @test !PeriodicGraphs.gaussian_elimination!(gausstrack, [4, 7])
     @test !PeriodicGraphs.gaussian_elimination!(gausstrack, [1, 3, 5])
     @test length(gausstrack.rings) == 4
-    @test PeriodicGraphs.gaussian_elimination(gausstrack, [1, 4, 5, 7])
-    @test PeriodicGraphs.gaussian_elimination!(gausstrack, [1, 4, 5, 7])
+    notindependent, info = PeriodicGraphs.gaussian_elimination(gausstrack, [1, 4, 5, 7])
+    @test notindependent
+    @test PeriodicGraphs.gaussian_elimination!(gausstrack, [1, 4, 5, 7], notindependent, info)
     @test PeriodicGraphs.retrieve_track!(gausstrack) == Int32[5, 4, 1]
     @test !PeriodicGraphs.gaussian_elimination!(gausstrack, [3, 5, 6, 7])
     @test !PeriodicGraphs.gaussian_elimination!(gausstrack, [2, 3])
-    @test !PeriodicGraphs.gaussian_elimination(gausstrack, [1, 2, 3])
+    @test !first(PeriodicGraphs.gaussian_elimination(gausstrack, [1, 2, 3]))
     @test !PeriodicGraphs.gaussian_elimination!(gausstrack, [1, 2, 3])
     @test PeriodicGraphs.gaussian_elimination!(gausstrack, [1, 2, 3])
     @test PeriodicGraphs.retrieve_track!(gausstrack) == Int32[9, 8]