mata equivalent of Stata's preserve?

[Bert Lloyd]

Dear Matalisters,

Is there an equivalent of Stata's preserve for Mata?

I am in a situation where it would be convenient to take a snapshot of all the objects in Mata's memory, and later restore Mata to this state.

Thanks,

Bert

[Joseph Coveney]

Is there an equivalent of Stata's preserve for Mata?

Not to my knowledge.

I am in a situation where it would be convenient to take a snapshot of all the objects in Mata's memory, and later restore Mata to this state.

You could try creating a pointer to each object and parking the pointers in an associative array for the time being, and then retrieving and dereferencing them all afterward.

You could also park functions and matrixes in a Mata library; here you could use a wildcard to refer to them all at once, but I'm not sure that this approach will preserve state (contents) of the matrixes.

It's a curious situation to be in. If you anticipate it again, you might want to consider working with Mata's object-oriented programming features, designing classes that can conveniently contain the pertinent scalars and matrixes (and their current states), functions etc. in a collection of instantiated objects that you can keep available in memory while you do something else and then return attention to them when ready. I don't think that you can serialze them to disc, though.

[John Mullahy]

You can save all existing global matrixes using mata matsave, e.g.

mata
mata matsave mywork *

and then reload them later using mata matuse.

See

help mata matsave

This will not save user-defined functions or other objects, however.

[Bert Lloyd]

Thanks Joseph Coveney and John Mullahy for your suggestions.

I should have mentioned that at least in this application I only need the matrices, not functions or other objects.

It's a curious situation to be in.

Agreed.

John Mullahy I had considered mata matsave but was concerned about the following in the helpfile:

These commands are for interactive use; they are not for use inside programs. See [M-5] fopen() for Mata's programming functions for reading and writing files.

I had considered something like the following:

1. create a "storage" file using fopen

fh = fopen("mySnapshot.myfile", "w")

2. List the contents of Mata's memory using mata describe.

mata describe

3a. Access the list somehow

// don't know this part

3.b Save each element of the list to "mySnapshot.myfile" along the lines of

fputmatrix(fh, X1)
fputmatrix(fh, X1)

possibly looping through the list, possibly something fancier

3.c close the snapshot file

fclose(fh)

4. [Do some other stuff until it's time to retrieve the objects]

5.a Open the snapshot file for reading

fh = fopen("mySnapshot.myfile", "r")

5.b retrieve each element

X1 = fgetmatrix(fh)
X2 = fgetmatrix(fh)

Is this a sensible thing to do?

If so, I'd appreciate some advice on implementing it, especially 3a and 3b.

[John Mullahy]

In my experience the Mata warnings about interactive use only

These commands are for interactive use; they are not for use inside programs. See [M-5] fopen() for Mata's programming functions for reading and writing files.

are sometimes not binding.

Consider this program

cap prog drop testmata
prog def testmata

mata: z=J(1,1,1)
mata: mata matsave zmat z, replace

end

Results:

. testmata
(saving z)
file zmat.mmat saved

[Bert Lloyd]

Thanks I will give that a try.