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  • mnist数据集下载

    http://yann.lecun.com/exdb/mnist/

    THE MNIST DATABASE

    of handwritten digits
    Yann LeCun, Courant Institute, NYU
    Corinna Cortes, Google Labs, New York
    Christopher J.C. Burges, Microsoft Research, Redmond
     

    The MNIST database of handwritten digits, available from this page, has a training set of 60,000 examples, and a test set of 10,000 examples. It is a subset of a larger set available from NIST. The digits have been size-normalized and centered in a fixed-size image.

    It is a good database for people who want to try learning techniques and pattern recognition methods on real-world data while spending minimal efforts on preprocessing and formatting.

    Four files are available on this site:  

    train-images-idx3-ubyte.gz:  training set images (9912422 bytes)
    train-labels-idx1-ubyte.gz:  training set labels (28881 bytes)
    t10k-images-idx3-ubyte.gz:   test set images (1648877 bytes)
    t10k-labels-idx1-ubyte.gz:   test set labels (4542 bytes)

    FILE FORMATS FOR THE MNIST DATABASE

    The data is stored in a very simple file format designed for storing vectors and multidimensional matrices. General info on this format is given at the end of this page, but you don't need to read that to use the data files.

    All the integers in the files are stored in the MSB first (high endian) format used by most non-Intel processors. Users of Intel processors and other low-endian machines must flip the bytes of the header.

    There are 4 files:

    train-images-idx3-ubyte: training set images
    train-labels-idx1-ubyte: training set labels
    t10k-images-idx3-ubyte:  test set images
    t10k-labels-idx1-ubyte:  test set labels

    The training set contains 60000 examples, and the test set 10000 examples.

    The first 5000 examples of the test set are taken from the original NIST training set. The last 5000 are taken from the original NIST test set. The first 5000 are cleaner and easier than the last 5000.

    TRAINING SET LABEL FILE (train-labels-idx1-ubyte):

    [offset] [type]          [value]          [description]
    0000     32 bit integer  0x00000801(2049) magic number (MSB first)
    0004     32 bit integer  60000            number of items
    0008     unsigned byte   ??               label
    0009     unsigned byte   ??               label
    ........
    xxxx     unsigned byte   ??               label

    The labels values are 0 to 9.

    TRAINING SET IMAGE FILE (train-images-idx3-ubyte):

    [offset] [type]          [value]          [description]
    0000     32 bit integer  0x00000803(2051) magic number
    0004     32 bit integer  60000            number of images
    0008     32 bit integer  28               number of rows
    0012     32 bit integer  28               number of columns
    0016     unsigned byte   ??               pixel
    0017     unsigned byte   ??               pixel
    ........
    xxxx     unsigned byte   ??               pixel

    Pixels are organized row-wise. Pixel values are 0 to 255. 0 means background (white), 255 means foreground (black).

    TEST SET LABEL FILE (t10k-labels-idx1-ubyte):

    [offset] [type]          [value]          [description]
    0000     32 bit integer  0x00000801(2049) magic number (MSB first)
    0004     32 bit integer  10000            number of items
    0008     unsigned byte   ??               label
    0009     unsigned byte   ??               label
    ........
    xxxx     unsigned byte   ??               label

    The labels values are 0 to 9.

    TEST SET IMAGE FILE (t10k-images-idx3-ubyte):

    [offset] [type]          [value]          [description]
    0000     32 bit integer  0x00000803(2051) magic number
    0004     32 bit integer  10000            number of images
    0008     32 bit integer  28               number of rows
    0012     32 bit integer  28               number of columns
    0016     unsigned byte   ??               pixel
    0017     unsigned byte   ??               pixel
    ........
    xxxx     unsigned byte   ??               pixel

    Pixels are organized row-wise. Pixel values are 0 to 255. 0 means background (white), 255 means foreground (black).
     


    THE IDX FILE FORMAT

    the IDX file format is a simple format for vectors and multidimensional matrices of various numerical types.

    The basic format is

    magic number
    size in dimension 0
    size in dimension 1
    size in dimension 2
    .....
    size in dimension N
    data

    The magic number is an integer (MSB first). The first 2 bytes are always 0.

    The third byte codes the type of the data:
    0x08: unsigned byte
    0x09: signed byte
    0x0B: short (2 bytes)
    0x0C: int (4 bytes)
    0x0D: float (4 bytes)
    0x0E: double (8 bytes)

    The 4-th byte codes the number of dimensions of the vector/matrix: 1 for vectors, 2 for matrices....

    The sizes in each dimension are 4-byte integers (MSB first, high endian, like in most non-Intel processors).

    The data is stored like in a C array, i.e. the index in the last dimension changes the fastest. 

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  • 原文地址:https://www.cnblogs.com/antflow/p/7298238.html
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