SIMULINK BUG, or Am I missing something in DATA STORE MEMORY block?

I have a Simulink model with the following problem:

At the top-level I have one data store memory block A, with one respective read and write block. And even though after the reading, the value travels thru a S-Function at the same level, 3 different Switch-Case Action Subsystems each one with different S-Functions, returns to top-level, and passes thru a Merge block, the writing of the new value is correct.

Now, inside just 1 of the 3 Switch-Case Action Subsystems I have another data store memory block B, also with one respective read and write block inside the subsystem too, same level. After the reading, the value travels thru the S-Function, together with the value from memory block A.

The value for block A is always correct. However, there is no reading from block B.

I already tried:

1-Changing the data type, in the memory block and the S-Function.

2-Double check in sample time.

3-Different initial value.

4-Set ports connected to Merge block as SS_REUSABLE_AND_GLOBAL.

5-Diffent computers (x32 and x64).

6-Put B at the same top-level with A.

7-The same problem still exists in a smaller model too.

But still not reading from block B. Is there something missing?

Anyone please. I am stuck with this for a week.

Thanks.

-Ele

Answer 1

[Nirmal Gunaseelan]

Looks to me like an access issue. How about you make B as a global data store? This is just to make sure that your conditionally executed subsystem has and provides access to B outside itself.

[Eleazar]

Thanks for your comment. It is an access issue, but not exactly with the data store.

The 3 Switch-Case Action Subsystems have different S-Functions (which btw have i/o access to a hard-disk file), and their output updates the data store. I think the speed how the S-Functions are computed is much slower than how the data stores are updated.

Now, I could fix this if I can stop propagation of the signal when they enter a Switch-Case Action Subsystem. But still cannot find out how to stop the propagation.

[Nirmal Gunaseelan]

It looks like a block execution order issue - the s-fcn that writes into the data stores are probably in the wrong order. Can you try switching on block execution order to see if all the ordering is as you expect? This can be done by Display menu -> Blocks -> Sorted Execution order being checked.

Once that is done, you could try setting block priority to ensure that the order you want is honored.

[Eleazar]

Well, I realized the problem is not about block execution order. Funny is that, in the initial run of the model, there is no reading from block B. But if I run the model a second time, it works perfectly.

I think there is an issue with how many S-fcn's can open same .txt file at the same time. 2 S-fcn's writing in the file work fine, but one more even just reading it maybe cannot if the file is empty. But as I said, in the second run, with some data in the file, the model runs fine.

I think that is why the data store memory block B is not updated from the output of the s-fcn. A third pointer to the same .txt file is not working. Btw, the s-fcn's are in C language.

This is just my guess. Maybe I am wrong.

[Kaustubha Govind]

Eleazar: Would it be simpler if you try to debug this by modifying your S-function to not perform file read/write access (because that may be a C-language related issue)? This might help you determine if it is really a file I/O issue or a Simulink issue.

Answer 2

[Muruganandham Subramanian]

How you are reading the value for DSR B (data store read)?? from workspace?? Is DSR B depends on DSR A output?, If it depends, check DSR memory used inside the subsytem, passing right value to DSR B ?

[Eleazar]

Values of DSR B are only in the Simulink model, and there is nothing from or to the workspace.

The original model is big, so I created a much reduced toy-model out of it, just to reproduce the problem. Just a few block and 2 DSM blocks. There is 1 .txt file accessed by the 3 S-fnc's (in C lang.), and ech S-fnc in a Switch-Case Action Subsystem. The S-fnc's are used to read and update a pointer to the .txt file, and i/o to the .txt file too. The pointer is stored in the DSM B.