Index select pytorch gather, and torch. index_select (dim, index) → Tensor ¶ See torch. However, the algorithm I wrote was several hundred times faster. chunk用于按指定尺寸分割张量，torch. torch. arange. r. I am willing to use index_select() if I can figure out how to get the index. 引言 最近在刷开源的Pytorch版动手学深度学习，里面谈到几个高级选择函数，如index_select，masked_select，gather等。这些函数大多很容易理解，但是对于gather函数，确实有些难理解，官方文档开始也看得一脸懵，感觉不太直观。下面谈谈我对这几个函数的一些 torch. Hi, I just found that calling index_select() on long columns (dim=1) are much slower than doing it on long rows (dim=0). We define indices as a 1D tensor containing 0 and 2, indicating we want In PyTorch, the . randint(0, 40000, size=(256, 2000)) 256 is the batch size. I have implemented a paper using this function but the result is quite How to indexing a tensor with a tensor in multi-dimension? Zhaoyi-Yan (Zhaoyi Yan) idx is the indexes for selecting the elements in the tensor. index_select函数顾名思义就是根据index索引在input输入张量中选择某些特定的元素，下面介绍该函数的参数。torch. Pytorch tensor indexing. index – the index to select with. index_select 是 PyTorch 中用于按索引选择张量元素的函数。它的作用是从输入张量中按照给定的索引值，选取对应的元素形成一个新的张量。它沿着一个维度选择元素，同时保持其他维度不变。也就 Given a = torch. This function returns a view of the original tensor with the given dimension How can this be done using the torch. pytorch 小技巧 index_select() 用法案例与解析. 71. index_select() function extracts specific elements from a tensor along a specified dimension based on indices and returns a new tensor. LongTensor([0, 2]) y = torch. Each 2D output pixel (ignoring batches for now) will copy a pixel in the input 2D image, according to a provided lookup tensor of 2D co-ordinates. 沿着张量的某个dim方向，按照index规定的选取指定的低一维度张量元素整体，在拼接成一个张量。其官方解释如下： torch. When performing indexing in PyTorch, you can use several types: Integers: These are used for selecting specific elements or slices in tensors. Here are weight tensor and index: W = torch. Syntax: torch. index_select(input, dim, index, out=None) input: The input tensor to select elements from. index_select(dim, indices) fixes the issue. I tested multiple versions of pytorch's index_select function against two possibly implementation using a CUDA extension that I wrote. index_select outperforms regular indexing when the tensor size is small, but is outperformed when the size is large. randn_like(输入Tensor,dtype=数据类型,device=设备对象)注意：这不能用整型来作为参数在 PyTorch 中，rand和randn_like用于生成浮点数类型的随机数，而randint用于生成整数类型的随机数，并且你可以指定整数的范围和数据类型。 最近加入了一个deeplearning的学习小组开始学习pytorch，初始对这个向量切片函数index_select()感到有些疑惑，经过自己一番实验之后，应该算是懂了吧，和大家一起分享一下实验结果。index_select有两种用法，一种是将某一个张量(tensor)作为变量传入torch. e. , 0 for rows, 1 for columns). 4. You can use the workaround until this issue is solved. I have a list of indices and a pytorch dataset (e. Hello, index_select allows me to retrieve rows of a tensor by 今天就跟大家聊聊有关index_select()函数怎么在pytorch中使用，可能很多人都不太了解，为了让大家更加了解，小编给大家总结了以下内容，希望大家根据这篇文章可以有所收获。 pytorch中index_select()的用法. , 40. 3. This works, when I build the index by hand: import torch from torch. cifar). Can the selected indexes of a tensor itself, but not the selected elements of indexes differentiable in PyTorch? So that I can select different indexes of a tensor by back propagation. So, for example, this snippet would rotate the corner pixels (the ones with values 40 to 43) of the input 4x4 image torch. Intro to PyTorch - YouTube Series Understanding the Types for Indexing. split按特定大小分割张量，以及torch torch. For example, a = b. still reproduce this and observed the performance gap is even bigger when the # of repeated indices increasing during selection. index_select 是 PyTorch 中的一个函数，用于根据指定的索引从输入张量中选择特定的行或列。它是一种非常灵活的张量操作工具，常用于数据筛选、特征提取等场景。 PyTorch tensor indexing is a powerful and flexible technique that enables you to select and modify specific elements or subsets of a tensor using different indexing schemes. rand(40000, 1024) index = torch. PyTorch Recipes. 可随时部署的 PyTorch 代码示例，小巧实用. index_select 是 PyTorch 中用于按索引选择张量元素的函数。它的作用是从输入张量中按照给定的索引值，选取对应的元素形成一个新的张量。它沿着一个维度选择元素，同时保持其他维度不变。也就是说:保留所有 1. index_select, torch. ; 2. I want as output a 2d tensor with the same number of rows as the input tensor and cols as the index tensor. PyTorch 食谱. index_select(input, dim, index, out=None): input：输入Tensor，在该Tensor上根据index和dim进行切片； dim：切片维 Copies the elements of ‘tensor’ into the ‘x’ by selecting the indices in the order given in ‘index’. , 50. index_select There are two types of index-based operations in PyTorch, one is in-place operations and the other is out-of-place operations. index_select 是 PyTorch 中用于按索引选择张量元素的函数。它的作用是从输入张量中按照给定的索引值，选取对应的元素形成一个新的张量。它沿着一个维度选择元素，同时保持其他维度不变。也就是说:保留所有其他维度的元素，但在索引张量 In pytorch I have a multi-dimensional tensor, call it X X = [[1, 2, 3], [4, 5, 6], [7, 8, 9], [10, 11, 12], ] Now I would like to select a different column index Run PyTorch locally or get started quickly with one of the supported cloud platforms. is there any possibility to achieve this? import torch # initialize tensor tensor = torch. 3w次，点赞9次，收藏32次。本文详细介绍Tensor在PyTorch中的基本索引操作，包括初级索引如选取行、列和元素，以及高级索引如使用index_select、masked_select、non_zero和gather函数进行复杂的数据筛选和处理。 输入Tensor. Explanation: Select 0th row from x[0], select 2nd row from x[1]. index_select ( input , dim , index , * , out = None ) → Tensor Returns a new tensor which indexes the input tensor along dimension dim using the entries in index which is a LongTensor . By mastering these simple techniques, you can easily access, modify, and Here is a solution if you want to index a tensor in an arbitrary dimension and select a set of tensors from that dimension (an example is say we want to compute some average of the first 3 layers): Still very new to PyTorch, but loving the style. index_select (input, dim, index, *, out = None) → Tensor ¶ Returns a new tensor which indexes the input tensor along dimension dim using the entries in index torch. How can this be done using the torch. Does anyone know why there is such a huge difference? Here is Hi all, when I am masking a sparse Tensor with index_select() in PyTorch 1. The [] operator is using that mask to select elements. 在本地运行 PyTorch 或通过受支持的云平台快速开始. PyTorch Forums Index_select, take all but specified indices? mbp28 (mbp28) August 10, 2018, 1:40pm 1. nonzero找出非零元素的索引，torch. index_select(input, dim, index, out=None) Parameters: input(Tensor): Tensor from which the indices will be We call torch. What it does. cat用于沿指定维度连接张量，torch. 假设输入参数dim=0, input为 torch. 文章浏览阅读2. When I used the indices to get a subset from the dataset, the new subset. index_select¶ torch. nonzero. index_select. index_select Assume I have a tensor sequences of shape [8, 12, 2]. Basically, let’s say I have a torch tensor like so: m = Variable(torch. Hi all, when I am masking a sparse Tensor with index_select() in PyTorch 1. size(0), B. If b wasn't a tensor, I could do: a[1,1,1,1] Which returns the correct cell, but: I have been looking far and wide for this kind of generalized indexing. 2. index_select(input, dim, index, out=None) 还有一种是调用张量内置的index_select()函数。 input. Understanding the Concept. as_tensor([[1,2,3,4,5], [6,7,8,9,0]]) index = [[0, 1, 1], [1, 1, 2]] # tensor([2, 7, 8]) x[index] Now I need index to be a tensor object, but doing this, I get an error: x = torch. index_select(x, 0, indices) print(y) z = torch. 可直接部署的 PyTorch 代码示例，小而精悍. gather、torch. PyTorch 教程中的新增内容. index_select(0, b) I don't understand why indexing with square brackets leads to illegal memory access, but this gives me enough reason to believe square-bracket indexing and index_select are implemented differently. size(1), A. Tensor. It looks like it needs some modification I could not figure it out at the moment. index_select(input, dim, index) torch. index_select は、テンソルの要素をインデックスのリストに基づいて選択するための関数です。この例では、tensor は 3 行 4 列のテンソルで、indices は 3 つのインデックス (1、0、2) を含むリストです。torch 在Pytorch中，index_select和gather均是被用于张量选取的常用函数，本文通过实例来对比这两个函数。 1. 学习基础知识. 1w次，点赞20次，收藏53次。目录一、通过索引获取值二、通过索引设置值在PyTorch C++ API（libtorch）中对张量进行索引的方式与Python API的方式很相似。诸如None / / integer / boolean / slice / tensor的索引类型在C++ API里同样有效，这样就可以很方便的实现Python代码与C++代码的转换。 PyTorch supports "Advanced Indexing. double() tens Hello, index_select allows me to retrieve rows of a tensor by specifying their respective indices. A is the matrix of indices of B, so this operation is essentially an indexing operation. index_select、torch. masked_select (input, mask, *, (BoolTensor) – the tensor containing the binary mask to index with. It is surely a way to solve it, however, I wonder whether pytorch can support a[idx], is it possible @albanD? pytorch函数之torch. Learn the Basics. src must be of the proper size in order to be embedded into input. as_tensor( [[0, 1, 1], [1, 1, 2]]) # IndexError: index 2 is out of bounds for dimension 0 with 1. gather(A, 1, dummy) There’s probably a simple way to do this, but owing to my noobness I do not know who to do this in PyTorch. view(3, 4) print(a Is this function differentiable? Is there any implementation code behind this function? I cannot find the source code of this function in the pytorch website. index_select 是 PyTorch 中用于按索引选择张量元素的函数。它的作用是从输入张量中按照给定的索引值，选取对应的元素形成一个新的张量。它沿着一个维度选择元素，同时保持其他维度不变。也就是说:保留所有其他维度的元素，但在索引张量 文章浏览阅读1. LongTensor of size 4] What I would like to do, is use the HI, torch uses same convention as numpy such for finding values or indices of particular tensor regarding specific condition. index_select和torch. index_select は、PyTorch の Tensor クラスにおいて、指定された次元とインデックスに基づいてテンソル要素を抽出するための関数です。 入力テンソルから特定の行または列を選択したり、特定の条件に基づいて要素を抽出したりするなど、さまざまな用途に使用できます。 torch. Familiarize yourself with PyTorch concepts and modules. ; index: A 1-D tensor pytorch按照指定元素索引排序选择操作大全（nonzero、sort、index_select函数），代码先锋网，一个为软件开发程序员提供代码片段和技术文章聚合的网站。 pytorch按照指定元素索引排序选择操作大全（nonzero、sort、index_select函数） - 代码先锋网 文章浏览阅读1w次，点赞16次，收藏31次。本文深入探讨了PyTorch中Tensor的维度理解，从一维到多维的构建过程，并详细介绍了简单索引、切片、bool tensor索引及花式索引的用法，帮助读者更好地掌握Tensor的操作。通过实例解析了不同类型的索引方式，包括数字索引、list索引、numpy数组索引、bool tensor I want to do something like this, but I need it be be differentiable w. view(3,4) print(x) indices = torch. nonzero()的定义 【摘自：Pytorch：torch. linspace(1, 12, steps=12). a[b] without all the extra operations PyTorch Tensor Indexing: Select Values by Last Dimension Indices . I could achieve In other words, matrix A is indexing and broadcasting matrix B. For all, we started with a simple 2D example, and also visualized the resulting selection graphically. index_select(input, dim, index) 功能:在指定的维度dim上选取数据,不如选取某些行,列 参数介绍. randn(10) b = a <= 0 indices = b. index_select (input, dim, index, out = None) """ Returns a new tensor which indexes the In this post we have seen three common selection methods in Pytorch: torch. Imagine you have two PyTorch tensors: Using torch. dataset still keeps the same length as the original dataset, even though when it is loaded into a dataloader, the length becomes correct. This seems to be very relevant for GNNs, since there are many node/edges/emb indexing. Keyword Arguments. Very surprised PyTorch doesn't support this natively, i. autograd import In this post we have seen three common selection methods in Pytorch: torch. index_select(dim, index) index_select()函数的作用是针对张量input，在它的dim维度上切取index指定的 torch. dataset. index_select(-1, c) Run PyTorch locally or get started quickly with one of the supported cloud platforms. index_select: A tensor is returned I have a multi-dimensional index b and want to use it to select a single cell in a. Motivation Index the input tensor along a given dimension using the entries in a multidimensional array of indices. ]) I found torch. tuero (Jake Tuero) January 11, 2025, 1 🚀 Feature Let index_select work with a multidimensional index. g. The returned tensor has the same number of dimensions as the original tensor I am confused about the Subset() for torch. 9k次，点赞15次，收藏17次。最近加入了一个deeplearning的学习小组开始学习pytorch，初始对这个向量切片函数index_select()感到有些疑惑，经过自己一番实验之后，应该算是懂了吧，和大家一起分享一下实验结果。index_select有两种用法，一种是将某一个张量(tensor)作为变量传入torch. index_select() You can use the torch. index_select with x as the input tensor, dim=0 to select rows, and indices to specify which rows to select. Example: A[0, 1] selects the element at the first row and second column. For the use case I originally built this for it was several thousand times faster! I was wondering if my algorithm could replace the current torch. Module where the input and outputs are both 2D grayscale images. index_select torch. nonzero()函数】 2. index_select: A tensor is returned with indices as mentioned, by selecting from the target tensor. The selection over dimension 1 is specified by indices stored in a long tensor indices of shape [8]. 第一个参数input是要索引查找的对象; 第二个参数dim是要查找的维度,因为通常情况下我们使用的都是二维张量,所以可以简单的记忆: 0代表行,1代表列 Demystifying torch. index_select(x, 1, indices) But the problem is that it is selecting the 0th and 2nd row for each item in x. This example below might help clarify: 文章浏览阅读2. a PyTorchでテンソルの一部を取得する：インデックススライシング、torch. Using index_select() requires that the PyTorch tensor indexing provides a rich set of indexing operations that enable you to select and modify tensor elements using different indexing schemes, such as integer indexing, boolean indexing, and advanced indexing. However, using x. randn(3, 2, 4, 5), how I can select sub tensor like (2, :, 0, :), (1, :, 1, :), (2, :, 2, :), (0, :, 3, :) (a resulting tensor of size (2, 4, 5) or (4 torch. Indexing one PyTorch tensor by another using index_select. index_select() method) to select multiple dimensions from a tensor and return a new tensor with the same number of torch. index_select和gather pytorch说明: index_select; gather index_select(input, dim, index) Returns a new tensor which indexes the input tensor along dimension dim using the entries in index which is a LongTensor. 1k次。是 PyTorch 中的一个非常有用的函数，允许从给定的维度中选择指定索引的张量值一个 1D 张量，包含你想要从dim维度中选择的索引此张量应该是LongTensor类型一个可选的参数，用于指定输出张量。如果没有提供，将创建一个新的张量。_pytorch index select Yes, in that case I can solve with gather but below case(x is 4-dim) I can’t solve with gather. I am stuck on a small problem where I cannot get the gradient or call backward() when using masked_select(). t the index-tensors. 是 PyTorch 中用于按索引选择张量元素的函数。它的作用是从输入张量中按照给定的索引值，选取对应的元素形成一个新的张量。它沿着一个维度选择元素，同时保持其他维度不变。也就 这篇博客介绍了PyTorch中的index_select函数，通过示例展示了如何在维度1上根据给定的索引选取数据。文章解释了参数含义，并给出了不同索引选择结果的示例。 pytorch索引查找 index_select. 教程. Understanding that could be Yes I did! I think the index attribute expects a tensor of all the classes for example if I have 10 classes, then it expects a tensor([0,1,2,3,4,5,6,7,8,9]). The extension outperforms all pyto I’m trying to write my own index_select to understand how this is done under the hood efficiently. zeros((1, 400, 400)). I think the old example is not correct to this problem, I changed it. dummy = B. Hi, I would like to know if it is possible to access multiple indexes across multiple dimensions in a single line using advance indexing/broadcasting techniques. take. In fact, for large enough matrices, it’s much faster to first transpose the matrix and call index_select() on rows! PyTorch 0. index_select¶ Tensor. unsqueeze(2). My use case is the following, I have an input image tensor (N, C, H_in, W_in), I have valid indexes tensors (N, H_out, W_out) for the height and width axes of the input image and I want to build an output image Now I would like to to access only the elements at specific indices, lets say at [0, 3, 4]. . In this post we have seen three common selection methods in Pytorch: torch. nonzero(). Suppose we have access to index(t, indices) where passing a list of raw integer indices will return a flattened tensor indexing into the passed tensor t. 1+cu117 Is debug build: False Indices in PyTorch help you efficiently work with data inside tensors, just like pointing to cells in a spreadsheet. index_select which worked great for a tensor of two dimensions, e. 9. new_ones(行,列,dtype=数据类型,device=设备对象)x = torch. index_select in PyTorch: Extracting Elements from Tensors . 方法 1: インデックススライシング PyTorchでは、ニューラルネットワークなどの計算をグラフ構造で表現します。 index的shape本来是(2,2), 里面的每个value被expand成了一个(3,4)的tensor, 故最后结果为shape为(2,2,3,4)的tensor. PyTorch version: 2. With all of these, one can select / index elements from a Tensor based on 文章浏览阅读2. Tutorials. 0. select_index(dim, index) 对于一个二维张量feature： 第一个参数 参数0表示按行索引，1表示按列进行索引 第二个参数 是一个整数类型的一维tensor，就是索引的序号 二维张量举例： 三维张量举例： 另一 torch. import torch a = torch. Now suppose my tensor is very large and I want almost all of these indices. Syntax 文章浏览阅读3. PyTorch 入门 - YouTube 系列. as_tensor([[1,2,3,4,5], [6,7,8,9,0]]) index = torch. masked_select实现按索引选取元素，torch. Syntax torch. Now I would like to make a selection of that tensor for each first dimension which results in a tensor of shape [8, 2]. size(0)), index] That essentially creates tuples between the enumerated tensor and your index tensor to access the data, which results in indexing output[0, 24], output[1, 10] etc. index_select(input, dim, index) 函数返回的 函数形式: index_select( dim, index ) 参数: dim:表示从第几维挑选数据,类型为int值: index:表示从第一个参数维度中的哪个位置挑选数据,类型为torch. Hi, I usually index tensors with lists of indices, like x = torch. Bite-size, ready-to-deploy PyTorch code examples. 通过我们引人入胜的 YouTube 教程系列掌握 PyTorch 基础知识 index_select()函数有两种用法。 第一种是将被切片的函数作为参数传入index_select()中. Hi, Say the column index is obtained though a network, and the loss is computed based on the selected columns from the matrix. where and torch. 12 documentation. index_select — PyTorch 1. I can do this by creating row and column index tensors, selecting from the input tensor, and then reshaping, but is there As you can see index_select for a dense tensor runs incredibly quickly, but the pytorch index_select is atrociously slow for sparse tensors. So I would like to return # exptected output tensor([10. What you can do is to apply your condition and get a binary mask of indices that match the condition and find the indices using torch. nonzero()用来筛选张量中符合某个条件的元素，得到这些元素的索引 一维例子： 注意得到的b是二维张量。 上述代码的原理是，a>6得到的是一个元素为True或 torch. Note. c = a[b] to. While torch. index_select() function? If the solution involves adding or permuting dimensions, that's fine. a = torch. " It implements the ability to accept a tensor argument to the [] operator. expand(B. PyTorch 教程的新内容. 7w次，点赞4次，收藏7次。本文详细介绍了PyTorch中的一些重要张量操作，包括torch. (Came from indices) I tried using index_select like this: torch. I don't think upstream pytorch would engage further on this However, the problem magically goes away when I change the indexing style from. format(x. post1, and GTX 1080). Its triggered by the fact that you use the max_index from the max operation that is not differential. index_select(y, 1 I am not able to understand how complex indexing - non contiguous indexing of a tensor works. out (Tensor, optional) – the output tensor. The result of the == operator is a boolean mask. Here is a sample code and its output import torch def describe(x): print(&quot;Type: {}&quot;. index_select. size(2)) out = torch. With all of these, one can select / index elements from a Tensor based on some condition. 熟悉 PyTorch 的概念和模块. torch. index_select()函数，还有一个是tensor的内置方法index_select。 在本地运行 PyTorch 或通过受支持的云平台快速开始. index_select is a function used to extract specific elements (rows or columns) from a tensor based on a 🐛 Describe the bug As the picture below shows, torch. randn(4,2)) Furthermore, I have a bunch of indices, given by inds, where inds is: inds Variable containing 1 1 0 0 [torch. ; dim: The dimension along which to index (e. Whats new in PyTorch tutorials. It builds a 256*N matrix (for various N) and rearranges its rows So index_select somehow discards the Variable state (or is it squeeze)? No its a problem (on pytorch side, not your code) in the way backward engine computes dependencies. arange(output. 是 PyTorch 中用于按索引选择张量元素的函数。它的作用是从输入张量中按照给定的索引值，选取对应的元素形成一个新的张量。它沿着一个维度选择元素，同时保持其他维度不变。也就是说:保留所有其他维度的元素，但在索引张量 torch. I tried this, however it selects each index in indices for each first dimension in sequences Run PyTorch locally or get started quickly with one of the supported cloud platforms. 2025-03-12 . 通过我们引人入胜的 YouTube 教程系列掌握 PyTorch 基础知识 torch. In PyTorch, the . index_select() function (or the Tensor. nonzero() 函数实现从当前张量中从某个维度选择一部分序号的张量 tensor. Tensor类的实例: 刚开始学习pytorch,遇到了index_select(),一开始不太明白几个参数的意思,后来查了一下资料,算是明白了一点. index_select(x, 1, indices) print(z) z = torch. 2. select (input, dim, index) → Tensor ¶ Slices the input tensor along the selected dimension at the given index. gather is more versatile, torch. gatherの徹底比較 . 4, the computation is much slower on a GPU (31 seconds) than a CPU (~6 seconds). This function works the same as index_add_() but instead of adding corresponding Hi! I’m trying to make my own nn. How Pytorch Tensor get the index of specific value. c = a. output[torch. Pytorch tensor - How to get the indexes by a specific tensor. PyTorch Forums Intuition behind index_select. Pytorch tensor indexing: How to gather rows by tensor containing indices. Pytorch中index_select() 函数的实现理解 函数形式: index_select( dim, index ) 参数: dim:表示从第几维挑选数据,类型为int值: index:表示从第一个参数维度中的哪个位置挑选数据,类型为torch. It operates along a designated dimension of the tensor. The basic difference between the two is in-place operation directly changes the values of the tensors without making any copy of that whereas out of place operations don’t. Whether you are working with large datasets or complex mathematical operations, PyTorch tensor indexing provides a simple and efficient way to manipulate tensor data. 4, the computation is much slower on a GPU (31 To select only one element per batch you need to enumerate the batch indices, which can be done easily with torch. I feel close with nonzero() but can’t quite get it to work. Specifically, it should I have tried two ways for batch index_select, but there are still some problems. 最新推荐文章于 2025-03-13 17:21:49 发布 I have a 2d input tensor and a 2d index tensor with the same number of rows where each value represents the column index I want to select. index_select は、テンソルの特定の次元を指定されたインデックスで選択するために使用できる関数です。 Pytorchには、2次元行列をインデックスする他にも様々な方法があります。詳しくはPytorchドキュメントを参照してください。 Just find a way to do this using gather:. 1k次，点赞2次，收藏3次。pytorch中index_select() 用法案例与解析index_select(input, dim, index)功能:在指定的维度dim上选取数据,不如选取某些行,列参数介绍第一个参数input是要索引查找的对象第二个参数dim是要查找的维度,因为通常情况下我们使用的都是二维张量,所以可以简单的记忆: 0代表行,1 🐛 Describe the bug pytorch's index_select function could be faster. index_select 関数を使用し PyTorchでGPUを利用する場合、主に2つの方法があります。CUDA モデルとデータをGPUメモリに転送し、GPU上で計算を実行します。DataParallel 複数のGPUにデータを分散させて並行処理を行い、計算速度を向上させます。 参数说明：index_select(x, 1, indices) 1代表维度1，即列，indices是筛选的索引序号。 例子： import torch x = torch. osdp jze ggwco lumzid edjup usaru jmyko cghdyd bumaskn uvn aycaxc tgmwx wnp mpk yliosze