speed up iszero (#494)

* speed up izero

* just use to_mpoly directly in iszero

* check to see if polynorm form is a Number, then check iszero

* bump symutils version

* (Number or MPoly) && iszero

Author: shashi

Project.toml

@@ -47,7 +47,7 @@ Requires = "1.0"
 SafeTestsets = "0.0.1"
 SpecialFunctions = "0.7, 0.8, 0.9, 0.10"
 StaticArrays = "0.10, 0.11, 0.12"
-SymbolicUtils = "0.4.1"
+SymbolicUtils = "0.4.3"
 TreeViews = "0.3"
 UnPack = "0.1, 1.0"
 Unitful = "1.1"

src/operations.jl

@@ -58,7 +58,11 @@ Base.hash(o::Operation, salt::UInt) = hash(o.args, hash(o.op, salt))
 
 # provide iszero for Operations to help sparse addition and multiplication
 # e.g., we want to tell the sparse library that iszero(zero(Operation) + zero(Operation)) == true
-Base.iszero(x::Operation) = (_x = simplify(x); _x isa Constant && iszero(_x.value))
+
+function Base.iszero(x::Operation)
+    _x = SymbolicUtils.to_mpoly(to_symbolic(x))[1]
+    return (_x isa Number || _x isa SymbolicUtils.MPoly) && iszero(_x)
+end
 
 Base.show(io::IO, O::Operation) = print(io, convert(Expr, O))