What is the fastest way to perform unary operation inplace?

General Usage Performance
1

What is the fastest way to perform unary operation inplace ?
I have tried the followings

b = rand(1000000)
@time b = -b
#  0.011017 seconds (2 allocations: 7.629 MiB)

@time b = (-).(b)
#  0.012952 seconds (2 allocations: 7.629 MiB)

@time b .-= 2 .* b
#  0.002173 seconds

@time begin
	for i in 1:length(b)
		@inbounds b[i] = -b[i]
	end
end
#  0.001698 seconds

the first and the second allocate a new array, the thrid use a trick that cannot be extended to all unary operators and the fourth is not as concise as one would like it to be.

2

Never mind i found it

@time @. b = -b
#  0.001678 seconds

# or
@time b .= (-).(b)
#  0.001670 seconds
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