Is beta schedule correctly defined?

[joanrod]

Hi all,

Am I wrong or the beta_schedule is not correct? https://github.com/Stability-AI/stablediffusion/blob/47b6b607fdd31875c9279cd2f4f16b92e4ea958e/ldm/modules/diffusionmodules/util.py#L24

It looks like a quadratic (pow 2) rather than linear.

linear_start = 0
linear_end = 1
betas = (np.linspace(linear_start ** 0.5, linear_end ** 0.5, n_timestep) ** 2)
x = np.linspace(linear_start, linear_end, n_timestep)
plt.plot(x, betas, n_timestep)
plt.ylim([0.0, 1.0])
plt.savefig("beta_schedule.png")