HIPS/autograd

support numpy.take

Open

#743 opened on Nov 24, 2025

View on GitHub
 (2 comments) (0 reactions) (0 assignees)Python (6,628 stars) (909 forks)batch import
PR welcomegood first issue

Description

Currently tracing the gradient through take is not supported:

import numpy as np
import autograd as ag
import autograd.numpy as anp

rng = np.random.default_rng(42)
x = rng.uniform(size=(3, 4, 5))
idx = rng.integers(0, 4, size=(6,))

def foo(x, idx):
    # # works:
    # return x[:, idx, :].sum()
    # # doesn't work:
    return anp.take(x, idx, axis=1).sum()

gfoo = ag.grad(foo, argnum=0)
gfoo(x, rng.integers(0, 4, size=(6,))).shape
# NotImplementedError: VJP of take wrt argnums (0,) not defined

take is mostly just a convenient syntax/subset of getitem indexing, so I suppose there is nothing fundamentally blocking it.

Contributor guide

Tech stack
python
Domain
machine learning
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
familiarity with autograd's VJP implementationunderstanding of numpy indexing
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60
Research direction
To implement VJP for numpy.take, first examine how existing VJPs for indexing operations (e.g., getitem ) are defined in autograd's source code, likely in the numpy wrapper module. Since take is a subset of getitem, the VJP can be derived by mapping take calls to equivalent getitem slices. Check the issue comments for any additional guidance. After implementing the VJP, add a test case similar to the provided reproducer to ensure correctness.