Computes log(1 - softmax(X)), accurately.

log1msoftmax.jl

"""
	log1msoftmax(X; dims=1)

Computes log(1 - softmax(X)), accurately.
"""
function log1msoftmax(x::AbstractArray; dims=1)
	@warn "log1msoftmax can have numerical issues, https://stats.stackexchange.com/questions/469706/log1-softmaxx/469803"
	#FIXME: https://stats.stackexchange.com/questions/469706/log1-softmaxx/469803?noredirect=1#comment867691_469803
    m = maximum(x; dims=dims)
	e = exp.(x .- m)
	s = sum(e; dims=dims)
	#return log.((s .- e) ./ s)
	return @. log1p(-e/s)
end