kalmar/Groups.jl
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New version of hash and ==

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evaluation of Automorphism on the standard basis is expensive

in hash(g::Automorphism, h::UInt) we
1. compute and store savedhash (evaluating f, if necessary) with a fixed value HASHINGCONST
2. xor h with savedhash

in == we evaluate f only at hash-colision (or when
This way we evaluate f multiple times only in ~2% of cases (for SAut(F_4))
This commit is contained in:
kalmarek 2018-03-27 20:14:24 +02:00
parent 6a7bb03d73
commit 7139322d05
1 changed files with 40 additions and 19 deletions
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59
src/AutGroup.jl
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@ -218,20 +218,54 @@ end
###############################################################################
#
# Basic manipulation
# Comparison
#
###############################################################################
const HASHINGCONST = 0x314a5215305f3ec1 # more or less random
hash(s::AutSymbol, h::UInt) = hash(s.str, hash(s.pow, hash(:AutSymbol, h)))
function hash(g::Automorphism, h::UInt)
if g.modified
g.savedhash = hash(g(domain(parent(g))), hash(typeof(g), hash(parent(g), h)))
g.modified = false
end
return g.savedhash
if g.modified
g.savedhash = hash(reduce!.(g(domain(parent(g)))),
hash(typeof(g), hash(parent(g), HASHINGCONST)))
g.modified = false
end
return xor(g.savedhash, h)
end
(==)(s::AutSymbol, t::AutSymbol) = s.str == t.str && s.pow == t.pow
function (==)(g::Automorphism{N}, h::Automorphism{N}) where N
parent(g) == parent(h) || return false
if !g.modified && !h.modified
if g.savedhash != h.savedhash
return false
end
end
# expensive:
g_im = reduce!.(g(domain(parent(g))))
h_im = reduce!.(h(domain(parent(h))))
# cheap:
g.savedhash = hash(g_im,
hash(typeof(g), hash(parent(g), HASHINGCONST)))
g.modified = false
h.savedhash = hash(h_im,
hash(typeof(h), hash(parent(h), HASHINGCONST)))
h.modified = false
return g_im == h_im
end
###############################################################################
#
# Basic manipulation
#
###############################################################################
function change_pow(s::AutSymbol, n::Int)
if n == 0
return id_autsymbol()
@ -266,19 +300,6 @@ function show(io::IO, G::AutGroup)
print(io, "Generated by $(join(G.gens, ","))")
end
###############################################################################
#
# Comparison
#
###############################################################################
(==)(s::AutSymbol, t::AutSymbol) = s.str == t.str && s.pow == t.pow
function (==)(g::Automorphism, h::Automorphism)
parent(g) == parent(h) || return false
return g(domain(parent(g))) == h(domain(parent(h)))
end
###############################################################################
#
# Binary operators