mindspore.nn.MaxPool1d

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class mindspore.nn.MaxPool1d(kernel_size=1, stride=1, pad_mode='valid', padding=0, dilation=1, return_indices=False, ceil_mode=False)[source]

Applies a 1D max pooling over an input Tensor which can be regarded as a composition of 1D planes.

Typically the input is of shape \((N_{in}, C_{in}, L_{in})\), MaxPool1d outputs regional maximum in the \((L_{in})\)-dimension. Given kernel size \(ks = (l_{ker})\) and stride \(s = (s_0)\), the operation is as follows:

\[\text{output}(N_i, C_j, l) = \max_{n=0, \ldots, l_{ker}-1} \text{input}(N_i, C_j, s_0 \times l + n)\]
Parameters

  • kernel_size (int) – The size of kernel used to take the max value, Default: 1 .

  • stride (int) – The distance of kernel moving, an int number that represents the width of movement is stride, Default: 1 .

  • pad_mode (str, optional) –

    Specifies the padding mode with a padding value of 0. It can be set to: "same" , "valid" or "pad" . Default: "valid" .

    • "same": Pad the input at the begin and end so that the shape of input and output are the same when stride is set to 1. The amount of padding to is calculated by the operator internally. If the amount is even, it is uniformly distributed around the input, if it is odd, the excess padding is goes to the right side. If this mode is set, padding must be 0.

    • "valid": No padding is applied to the input, and the output returns the maximum possible length. Extra pixels that could not complete a full stride will be discarded. If this mode is set, padding must be 0.

    • "pad": Pad the input with a specified amount. In this mode, the amount of padding at the begin and end is determined by the padding parameter. If this mode is set, padding must be greater than or equal to 0.

  • padding (Union(int, tuple[int], list[int])) – Padding value for the pooling. Default value is 0. padding can only be an integer or a tuple/list containing a single integer, in which case padding times or padding[0] times are padded on both sides of the input.

  • dilation (Union(int, tuple[int])) – The spacing between the elements of the kernel in convolution, used to increase the receptive field of the pooling operation. If it is a tuple, its length can only be 1. Default: 1 .

  • return_indices (bool) – If True , the function will return both the result of max pooling and the indices of the max elements. Default: False .

  • ceil_mode (bool) – If True, use ceil to compute the output shape instead of floor. Default: False .

Inputs:

  • x (Tensor) - Tensor of shape \((N, C_{in}, L_{in})\) or \((C_{in}, L_{in})\).

Outputs:

If return_indices is False, output is a Tensor, with shape \((N, C_{out}, L_{out})\) or \((C_{out}, L_{out})\). It has the same data type as x.

If return_indices is True, output is a Tuple of 2 Tensors, representing the maxpool result and where the max values are generated.

  • output (Tensor) - Maxpooling result, with shape \((N, C_{out}, L_{out})\) or \((C_{out}, L_{out})\). It has the same data type as x.

  • argmax (Tensor) - Index corresponding to the maximum value. Data type is int64.

If pad_mode is in pad mode, the output shape calculation formula is as follows:

\[L_{out} = \left\lfloor \frac{L_{in} + 2 \times \text{padding} - \text{dilation} \times (\text{kernel_size} - 1) - 1}{\text{stride}} + 1\right\rfloor\]
Raises

  • TypeError – If kernel_size or strides is not an int.

  • ValueError – If pad_mode is not "valid", "same" or "pad", case-insensitive.

  • ValueError – If data_format is neither 'NCHW' nor 'NHWC'.

  • ValueError – If kernel_size or strides is less than 1.

  • ValueError – If length of shape of x is not equal to 2 or 3.

  • ValueError – If pad_mode is not "pad", padding, dilation, return_indices, ceil_mode parameters are not set to their default values.

  • ValueError – If the length of the tuple/list padding parameter is not 1.

  • ValueError – If The length of the tuple dilation parameter is not 1.

  • ValueError – If dilation parameter is neither an integer nor a tuple.

  • ValueError – If padding is non-zero when pad_mode is not "pad".

Supported Platforms:

Ascend GPU CPU

Examples

>>> import mindspore as ms
>>> import mindspore.nn as nn
>>> import numpy as np
>>> mpool1 = nn.MaxPool1d(kernel_size=3, stride=1)
>>> x = ms.Tensor(np.random.randint(0, 10, [1, 2, 4]), ms.float32)
>>> output = mpool1(x)
>>> result = output.shape
>>> print(result)
(1, 2, 2)
>>> np_x = np.random.randint(0, 10, [5, 3, 4])
>>> x = ms.Tensor(np_x, ms.float32)
>>> mpool2 = nn.MaxPool1d(kernel_size=2, stride=1, pad_mode="pad", padding=1, dilation=1, return_indices=True)
>>> output = mpool2(x)
>>> print(output[0].shape)
(5, 3, 5)
>>> print(output[1].shape)
(5, 3, 5)