我必须在MATLAB中创建和存储几个矩阵。如果我选择使用多维数组，那么我就会遇到内存问题。如果我选择去一个单元格，那么代码非常慢。如何提高计算速度和内存使用率？
这是我的代码的简化版本
%%%%% MAIN FILE %%%%%%
rng default; %for reproducibility
%% Paramaters
N=20;
M=400;
R=M/2;
B=M/2;
%% Generate the matrix data of dimension NM x(1+1+N +(N-1)+(N-1))
data=[kron((1:1:M)', ones(N,1)) repmat((1:1:N)', M,1) randn(M*N, N +(N-1)+(N-1))];
%% Generate the matrix unob of dimension NMx(1+1+N-1)xR
unob=[repmat(data(:,1:2),1,1,R) randn(M*N,N-1,R)];
%% Option 1: MEMORY PROBLEM
%bootdata1 and bootunob1 have respectively dimension NMx(1+1+N +(N-1)+(N-1))xB and NMx(1+1+N-1)xRxB
[bootdata1, bootunob1]=boot1(N,M,B,R,data, unob);
%% Option 2: SLOW, NEVER ENDING
%bootdata is a matrix of dimension NMx(1+1+N +(N-1)+(N-1))xB
%bootunob is a cell of dimension Bx1 with bootunob{b} that is a matrix of dimension NMx(1+1+N-1)
[bootdata, bootunob]=boot(N,M,B,R,data, unob) ;
功能boot1
function [bootdata, bootunob]=boot1(N,M,B,R,data, unob)
%Allocate space
bootdata=zeros(N*M,1+1+N+(N-1)+(N-1), B);
bootunob=zeros(N*M,(1+1+N-1),R,B);
for b=1:B
%Draw uniformly at random with replacement M integers from {1,...,M} and
%store them into the vector networkindices of dimension 1xM
networkindices =randi([1 M],M,1);
%Fill bootdata(:,:,b) and bootunob(:,:,:,b)
for m=1:M
bootdata((m-1)*N+1:m*N, :,b)=data(data(:,1)==networkindices(m),:);
bootdata((m-1)*N+1:m*N,1,b)=m*(ones(N,1)); %change indices
for r=1:R
bootunob((m-1)*N+1:m*N, :,r,b)=unob(unob(:,1,r)==networkindices(m),:,r);
bootunob((m-1)*N+1:m*N,1,r,b)=m*(ones(N,1));
end
end
end
end
功能boot：
function [bootdata, bootunob]=boot(N,M,B,R,data, unob)
%Allocate space
bootdata=zeros(N*M,1+1+N+(N-1)+(N-1), B);
bootunob=cell(B,1);
for b=1:B
bootunob{b}=zeros(N*M,(1+1+N-1),R) ;
%Draw uniformly at random with replacement M integers from {1,...,M} and
%store them into the vector networkindices of dimension 1xM
networkindices =randi([1 M],M,1);
%Fill bootdata(:,:,b) and bootunob{b}
for m=1:M
bootdata((m-1)*N+1:m*N, :,b)=data(data(:,1)==networkindices(m),:);
bootdata((m-1)*N+1:m*N,1,b)=m*(ones(N,1)); %change indices
for r=1:R
bootunob{b}((m-1)*N+1:m*N, :,r)=unob(unob(:,1,r)==networkindices(m),:,r);
bootunob{b}((m-1)*N+1:m*N,1,r)=m*(ones(N,1));
end
end
end
end
答案 0 :(得分：1)
新方法
显着更快，我的计算机上的写入速度大约为100-300MB / s，尽管瓶颈已经成为代码的一部分，请参阅本节末尾的评论。
新的bootFaster方法：
function [bootDataFiles, bootUnobFiles] = bootFaster(N, M, B, R, data, unob)
% Temporary Variables
% Based on some simple math, these slices should be OKish. This will
% crash and burn if you try to use the save with files greater than
% 2^31 bytes, so just be careful with that.
bootDataTemp = zeros(N*M, 1+1+N+(N-1)+(N-1), 1);
bootUnobTemp = zeros(N*M, 1+1+(N-1), R, 1);
% Matricies containing the file names for the .mat files. There are B
% rows.
bootDataFiles = zeros(B, 17);
bootUnobFiles = zeros(B, 17);
for b = 1:B
networkIndices = randi([1 M], M, 1);
for m = 1:M
bootDataTemp((m-1)*N+1:m*N, :) = data(data(:, 1) == networkIndices(m), :);
bootDataTemp((m-1)*N+1:m*N, 1) = m * (ones(N, 1)); %change indices
for r = 1:R
bootUnobTemp((m-1)*N+1:m*N, :, r) = unob(unob(:, 1, r) == networkIndices(m), :, r);
bootUnobTemp((m-1)*N+1:m*N, 1, r) = m * (ones(N, 1));
end
end
% Creates the file name for the bth matrix.
% NOTE: if you change the 5 it will change the length of each file
% name, you will have to change the number of columns in
% bootDataFiles and bootUnobFiles accordingly.
bootDataFileB = sprintf('bootData%5.i.mat', b);
bootUnobFileB = sprintf('bootUnob%5.i.mat', b);
% Writes the contents of the tempoary variables to the file
save(bootDataFileB, 'bootDataTemp', '-v6');
save(bootUnobFileB, 'bootUnobTemp', '-v6');
% Storing the file names.
bootDataFiles(b, :) = bootDataFileB;
bootUnobFiles(b, :) = bootUnobFileB;
end
% Convert the values back to chars (each row will not be a "string")
bootDataFiles = char(bootDataFiles);
bootUnobFiles = char(bootUnobFiles);
end
要使用此数据，您现在可以使用matfile方法，如下所示。
[bootDataFiles, bootUnobFiles] = bootFaster(N,M,B,R,data, unob);
bootDataAtbFile = matfile(bootDataFiles(b, :));
% Note the use of "bootDataTemp" to access the data, you have to use
% the name of the temporary variable that you stored the data in inside
% bootFaster. E.g. to access the bootUnob data you would have to use
% bootUnobTemp, or whatever you choose to rename them to.
bootDataAtb = bootDataAtbFile.bootDataTemp;
最后的说明。这一行：
bootUnobTemp((m-1)*N+1:m*N, :, r) = unob(unob(:, 1, r) == networkIndices(m), :, r);
非常慢。例如。 N = 30且M = 200.该行占用执行时间的2/3。 高度会建议您查看是否可以重构此内容。
旧方法 - 由于压缩而在2015b中太慢
使用matfile函数和写入文件的能力变得非常容易实现。你必须改变你的代码并不多。请参阅下面的代码，了解它的工作原理。
在您的主要文件中，您需要执行以下操作：
file = bootFast(N,M,B,R,data, unob);
bootdata1F = file.bootdata;
bootunob1F = file.bootunob;
和bootFast：
function file = bootFast(N, M, B, R, data, unob)
% Opens the file, or creates it if it doesn't exsit
file = matfile('output', 'Writable', true);
% Sets the sizes of the variables
file.bootdata(N*M, 1+1+N+(N-1)+(N-1), B) = 0;
file.bootunob(N*M, 1+1+(N-1), R, B) = 0;
bootdataTemp = file.bootdata(:, :, 1);
bootunobTemp = file.bootunob(:, :, :, 1);
for b = 1:B
networkindices = randi([1 M], M, 1);
for m = 1:M
bootdataTemp((m-1)*N+1:m*N, :) = data(data(:, 1) == networkindices(m), :);
bootdataTemp((m-1)*N+1:m*N, 1) = m * (ones(N, 1)); %change indices
for r = 1:R
bootunobTemp((m-1)*N+1:m*N, :, r) = unob(unob(:, 1, r) == networkindices(m), :, r);
bootunobTemp((m-1)*N+1:m*N, 1, r) = m * (ones(N, 1));
end
end
file.bootdata(:, :, b) = bootdataTemp;
file.bootunob(:, :, :, b) = bootunobTemp;
end
end
我有限的磁盘写入每次只发生一次，试图加快速度，但你可能需要根据你拥有的内存来确定具体位置。
P.S。我希望你有一个SSD。