Taking the Inverse of a Tall Array To Solve a Linear System of Equations

Question

Ayden Clay 2020-5-23

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/530823-taking-the-inverse-of-a-tall-array-to-solve-a-linear-system-of-equations

编辑： Ayden Clay 2020-5-23

Hi, I'm working with some large data sets and have begun using tall arrays for the first time. I was happy to hear that the inverse function (\) was available for tall arrays, but am having some trouble on implementation. Below is a none-working example (you may need to set your own output directory), if F is tall or not doesn't change anything.

function [SOL] = MinWorkExample
outDIR = 'M:\project\MATLAB Folder\PhD\TESTAREA\InterpolationForPaper\PHFtall';
fileIDX = 1;
rowsPerFile = 1e3;
rowsWritten = 0;
totalRows = 1e5;
while rowsWritten<totalRows
    rowsToWrite = min(rowsPerFile, totalRows-rowsWritten);
    datas = rand(1,totalRows);
    fname = fullfile(outDIR,sprintf('datas_%05d.mat',fileIDX));
    save(fname,'datas');
    fileIDX = 1 + fileIDX;
    rowsWritten = rowsToWrite + rowsWritten;
end
ds = fileDatastore(fullfile(outDIR, '*.mat'), ...
    'ReadFcn', @(fname) getfield(load(fname), 'datas'), ...
    'UniformRead', true);
CONMAT = tall(ds);
% Either F does not work.
% F = rand(totalRows,1);
F = tall(rand(totalRows,1));
SOL = CONMAT\F;

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Answer 1

Ayden Clay 2020-5-23

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/530823-taking-the-inverse-of-a-tall-array-to-solve-a-linear-system-of-equations#answer_436828

在 MATLAB Online 中打开

So! I'm a collossal idiot. The error note was incredibly well written, and described my exact problem. Turns out that if I repeat the process but write in columns rather than rows, we're all good.

In the same nomenclature as the question, here is a working version:

function [SOL] = MinWorkExample
outDIR = '\PHFtall';
fileIDX = 1;
ColsPerFile = 1e3;
ColsWritten = 0;
totalCols = 1e5;
while ColsWritten<totalCols
    colsToWrite = min(ColsPerFile, totalCols-ColsWritten);
    datas = rand(totalCols,1);
    fname = fullfile(outDIR,sprintf('datas_%05d.mat',fileIDX));
    save(fname,'datas');
    fileIDX = 1 + fileIDX;
    ColsWritten = colsToWrite + ColsWritten;
end
ds = fileDatastore(fullfile(outDIR, '*.mat'), ...
    'ReadFcn', @(fname) getfield(load(fname), 'datas'), ...
    'UniformRead', true);
CONMAT = tall(ds);
F = tall(rand(1,totalCols));
SOL = CONMAT\F;