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[Nonlinear] remove recursion when parsing expressions #2020

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Oct 18, 2022
Merged

[Nonlinear] remove recursion when parsing expressions #2020

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61 changes: 38 additions & 23 deletions src/Nonlinear/parse.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -42,25 +42,38 @@ function parse_expression(
x::Expr,
parent_index::Int,
)
stack = Tuple{Int,Any}[]
push!(stack, (parent_index, x))
while !isempty(stack)
parent, item = pop!(stack)
if item isa Expr
_parse_expression(stack, data, expr, item, parent)
else
parse_expression(data, expr, item, parent)
end
end
return
end

function _parse_expression(stack, data, expr, x, parent_index)
if isexpr(x, :call)
if length(x.args) == 2 && !isexpr(x.args[2], :...)
_parse_univariate_expression(data, expr, x, parent_index)
_parse_univariate_expression(stack, data, expr, x, parent_index)
else
_parse_multivariate_expression(data, expr, x, parent_index)
_parse_multivariate_expression(stack, data, expr, x, parent_index)
end
elseif isexpr(x, :comparison)
_parse_comparison_expression(data, expr, x, parent_index)
_parse_comparison_expression(stack, data, expr, x, parent_index)
elseif isexpr(x, :...)
_parse_splat_expression(data, expr, x, parent_index)
_parse_splat_expression(stack, data, expr, x, parent_index)
elseif isexpr(x, :&&) || isexpr(x, :||)
_parse_logic_expression(data, expr, x, parent_index)
_parse_logic_expression(stack, data, expr, x, parent_index)
else
error("Unsupported expression: $x")
end
return
end

function _parse_splat_expression(data, expr, x, parent_index)
function _parse_splat_expression(stack, data, expr, x, parent_index)
@assert isexpr(x, :...) && length(x.args) == 1
if parent_index == -1
error(
Expand All @@ -74,13 +87,14 @@ function _parse_splat_expression(data, expr, x, parent_index)
"`(x + 1)...`, `[x; y]...` and `g(f(y)...)` are not.",
)
end
for xi in x.args[1]
parse_expression(data, expr, xi, parent_index)
for xi in reverse(x.args[1])
push!(stack, (parent_index, xi))
end
return
end

function _parse_univariate_expression(
stack::Vector{Tuple{Int,Any}},
data::Model,
expr::Expression,
x::Expr,
Expand All @@ -91,17 +105,18 @@ function _parse_univariate_expression(
if id === nothing
# It may also be a multivariate operator like * with one argument.
if haskey(data.operators.multivariate_operator_to_id, x.args[1])
_parse_multivariate_expression(data, expr, x, parent_index)
_parse_multivariate_expression(stack, data, expr, x, parent_index)
return
end
error("Unable to parse: $x")
end
push!(expr.nodes, Node(NODE_CALL_UNIVARIATE, id, parent_index))
parse_expression(data, expr, x.args[2], length(expr.nodes))
push!(stack, (length(expr.nodes), x.args[2]))
return
end

function _parse_multivariate_expression(
stack::Vector{Tuple{Int,Any}},
data::Model,
expr::Expression,
x::Expr,
Expand All @@ -111,13 +126,12 @@ function _parse_multivariate_expression(
id = get(data.operators.multivariate_operator_to_id, x.args[1], nothing)
if id === nothing
@assert x.args[1] in data.operators.comparison_operators
_parse_inequality_expression(data, expr, x, parent_index)
_parse_inequality_expression(stack, data, expr, x, parent_index)
return
end
push!(expr.nodes, Node(NODE_CALL_MULTIVARIATE, id, parent_index))
parent_var = length(expr.nodes)
for i in 2:length(x.args)
parse_expression(data, expr, x.args[i], parent_var)
for i in length(x.args):-1:2
push!(stack, (length(expr.nodes), x.args[i]))
end
return
end
Expand All @@ -126,16 +140,16 @@ end
# confused with `_parse_comparison_expression`, which handles things like
# `a <= b <= c`.
function _parse_inequality_expression(
stack::Vector{Tuple{Int,Any}},
data::Model,
expr::Expression,
x::Expr,
parent_index::Int,
)
operator_id = data.operators.comparison_operator_to_id[x.args[1]]
push!(expr.nodes, Node(NODE_COMPARISON, operator_id, parent_index))
parent_var = length(expr.nodes)
for i in 2:length(x.args)
parse_expression(data, expr, x.args[i], parent_var)
for i in length(x.args):-1:2
push!(stack, (length(expr.nodes), x.args[i]))
end
return
end
Expand All @@ -144,6 +158,7 @@ end
# confused with `_parse_inequality_expression`, which handles things like
# `a <= b`.
function _parse_comparison_expression(
stack::Vector{Tuple{Int,Any}},
data::Model,
expr::Expression,
x::Expr,
Expand All @@ -154,14 +169,14 @@ function _parse_comparison_expression(
end
operator_id = data.operators.comparison_operator_to_id[x.args[2]]
push!(expr.nodes, Node(NODE_COMPARISON, operator_id, parent_index))
parent_var = length(expr.nodes)
for i in 1:2:length(x.args)
parse_expression(data, expr, x.args[i], parent_var)
for i in length(x.args):-2:1
push!(stack, (length(expr.nodes), x.args[i]))
end
return
end

function _parse_logic_expression(
stack::Vector{Tuple{Int,Any}},
data::Model,
expr::Expression,
x::Expr,
Expand All @@ -170,8 +185,8 @@ function _parse_logic_expression(
id = data.operators.logic_operator_to_id[x.head]
push!(expr.nodes, Node(NODE_LOGIC, id, parent_index))
parent_var = length(expr.nodes)
parse_expression(data, expr, x.args[1], parent_var)
parse_expression(data, expr, x.args[2], parent_var)
push!(stack, (parent_var, x.args[2]))
push!(stack, (parent_var, x.args[1]))
return
end

Expand Down
14 changes: 14 additions & 0 deletions test/Nonlinear/Nonlinear.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -870,6 +870,20 @@ function test_eval_atan2()
return
end

function test_deep_recursion()
model = Nonlinear.Model()
x = MOI.VariableIndex(1)
y = Expr(:call, :sin, x)
for _ in 1:20_000
y = Expr(:call, :^, Expr(:call, :sqrt, y), 2)
end
start = time()
@test Nonlinear.parse_expression(model, y) isa Nonlinear.Expression
# A conservative bound to check we're not doing something expensive.
@test time() - start < 1.0
return
end

end

TestNonlinear.runtests()
Expand Down