Non Scalar Structures

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Pankaj 2012-2-16

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https://ww2.mathworks.cn/matlabcentral/answers/29282-non-scalar-structures

回答： upol 2019-1-10

Hi how can I save a non scalar structures. Again, I don't really know what a nonscalar structure is. I know mine is a nonscalar structure because save('filename',-struct,'structname) throws exception saying your structure is nonscalar.

I am trying to save a matrix of structures each structure has a structure inside it. does such programming increase runtime?

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Answer 1

Jan 2012-2-16

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No, such programming does not necessarily increase the runtime. It can be a nice and efficient structure to represent the data. Even if it runs some seconds slower, a clear data representation can save weeks of debugging.

A non-scalar struct is something like this:

S(1,1).a = 1;
S(2,1).a = 2;
S(1,2).a = 3;
S(2,2).a = 4;

Now you have a [2x2] struct with the field 'a'. You cannot save this using the '-struct' flag, but by:

save('filename.mat', 'S');

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Pankaj 2012-2-19

Hi Jan, sorry for late reply.

The code you posted works. I was doing a mistake passing S without single quotes. The issue however is, that this still doesn't solve the problem. It takes Matlab more than half an hour to save the variable.The size of the structure in Bytes is close 5.75 GB.

Any suggestions? thanks

Jan 2012-2-19

Writing 5.75 GB to a disk takes some time. Do you write the MAT file in the -7.3 format (see "help save", if this is not clear)? You cannot use the faster -v6 flag for SAVE, because even the compressed file is larger than 2GB already.

If your staruct has a lot of elements (millions), consider that each element has more than 100 Bytes overhead. E.g.:

[S(1:1e4).a] = deal(1); T.a(1:1e4) = 1; whos

You have 1200064 Bytes for S and 80176 bytes for T. A struct of fields consumes less memory than a field of structs. This matters the requirements of RAM, of disk-space when using SAVE and even the processing speed depends on the internal data representation.

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