File size: 1,359 Bytes
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function [labels, images] = read_mnist8m_libsvm_parallel(filename, num_samples)
% Open file and read all lines in one go (fast)
fid = fopen(filename, 'r');
if fid == -1
error('Could not open file.');
end
data = textscan(fid, '%s', num_samples, 'Delimiter', '\n');
fclose(fid);
data = data{1}; % Extract cell array of strings
labels = zeros(num_samples, 1, 'uint8'); % Labels
images = zeros(num_samples, 784, 'uint8'); % Preallocate matrix for images
% Start parallel processing
parfor i = 1:num_samples
line = data{i}; % Extract current line
parts = strsplit(line, ' '); % Split line into parts
% First part is the label
labels(i) = str2double(parts{1});
% Remaining parts are pixel index:value pairs
pixel_data = parts(2:end);
pixel_info = split(pixel_data, ':'); % Efficient parsing of indices and values
indices = str2double(pixel_info(:, :, 1)); % Convert indices to numeric
values = str2double(pixel_info(:, :, 2)); % Convert values to numeric
% Assign pixel values in a local temporary array
temp_img = zeros(1, 784, 'uint8');
temp_img(indices) = values;
% Store the processed image in the main matrix
images(i, :) = temp_img;
end
end
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