Diffusers.jl/test/BetaSchedules.jl

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using Diffusers.BetaSchedules
using Test
@testset "Variance schedules tests" begin
@testset "SNR decreases monotonically" begin
T = 1000
β_linear = linear_beta_schedule(T)
β_scaled_linear = scaled_linear_beta_schedule(T)
β_cosine = cosine_beta_schedule(T)
β_sigmoid = sigmoid_beta_schedule(T)
α̅_linear = cumprod(1 .- β_linear)
α̅_scaled_linear = cumprod(1 .- β_scaled_linear)
α̅_cosine = cumprod(1 .- β_cosine)
α̅_sigmoid = cumprod(1 .- β_sigmoid)
# arxiv:2208.11970 Eq. 109
SNR_linear = α̅_linear ./ (1 .- α̅_linear)
SNR_scaled_linear = α̅_scaled_linear ./ (1 .- α̅_scaled_linear)
SNR_cosine = α̅_cosine ./ (1 .- α̅_cosine)
SNR_sigmoid = α̅_sigmoid ./ (1 .- α̅_sigmoid)
@test all(diff(SNR_linear) .<= 0)
@test all(diff(SNR_scaled_linear) .<= 0)
@test all(diff(SNR_cosine) .<= 0)
@test all(diff(SNR_sigmoid) .<= 0)
end
end