torch.digamma

torch.digamma(input, *, out=None) → Tensor

Computes the logarithmic derivative of the gamma function on input.

$$\psi(x) = \frac{d}{dx} \ln\left(\Gamma\left(x\right)\right) = \frac{\Gamma'(x)}{\Gamma(x)}$$

Parameters

input (Tensor) – the tensor to compute the digamma function on

Keyword Arguments

out (Tensor, optional) – the output tensor.

Note

This function is similar to SciPy’s scipy.special.digamma.

Note

From PyTorch 1.8 onwards, the digamma function returns -Inf for 0. Previously it returned NaN for 0.

Example:

>>> a = torch.tensor([1, 0.5])
>>> torch.digamma(a)
tensor([-0.5772, -1.9635])