Convert State to Stateful Parameter

[mraunak]

Overview

Bring in the concept of Stateful Parameters instead of State. The Node object will have Function and Parameter, and further Parameter is categorized as Stateful and fixed Parameter. Stateful Parameter stores the value and changes with time.

Step1: Create Stateful Parameter

• Change the time derivative to change in value of parameter and output the updated value
• Rename existing scheduler to execution_engine to perform calculation
• Link with standalone repo of scheduler for scheduling the next execution
• Pull to development branch

Step2: Write the Translator

• Convert dv/dt to incremental format
• Define a translator that converts states file into stateful parameters file

[Shanka123]

Apart from parameters nodes also have stateful parameters whose values are associated with a function and evolves with time as the graph is evaluated.
.
A stateful parameter has the following components:

1. id
2. default initial value to start with
3. value updated by a MDF function that uses the previous value of the stateful parameter, time increment (dt)

Initial work on this here: https://github.com/ModECI/MDF/tree/stateful_parameter

Initial thoughts on implementing the translator:

1. Input should be any json file with implementation of states.
2. Extract the parameters / arguments from the expression of time derivative, parameters field of the nodes.
3. Create a new MDF function using the expression of time derivative for each state, extracted arguments.

[jdcpni]

A couple of comments (if there is a better mechanism for providing comments, please let me know): a) There should be no specific requirement that a stateful parameter is associated with one or more functions, though its state will of course not change if it is not. The only implementational requirement for a stateful parameter (that is, that must be implemented by the execution environment) is that its value is maintained from one execution to the next. b) The functions that take and return stateful parameters need not have time and dt as parameters, though if they take one, they should take the other, and should also be associated with a derivative (though we have not yet formalized how that will be; one possibility is that the expression for a derivative can be an attribute of a function, in which case the triad of: time argument, dt argument, derivative attribute should always go together).

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Sent from my iPad On Jul 8, 2021, at 9:24 PM, Shanka Subhra Mondal ***@***.***> wrote:  Apart from parameters nodes also have stateful parameters whose values are associated with a function and evolves with time as the graph is evaluated. . A stateful parameter has the following components: 1. id 2. default initial value to start with 3. value updated by a MDF function that uses the previous value of the stateful parameter, time increment (dt) Initial work on this here: Initial thoughts on implementing the translator: 1. Input should be any json file with implementation of states. 2. Extract the parameters / arguments from the expression of time derivative, parameters field of the nodes. 3. Create a new MDF function using the expression of time derivative for each state, extracted arguments. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub<#89 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ACSHKGEJ4ZFOCB6TYEY4QFLTWZFV5ANCNFSM5ABVUE7Q>.

[Shanka123]

Translator has been implemented and tested successfully. Translator converts files with state if it contains to file with stateful parameters, otherwise unchanged. The output file upon evaluation produces the same results.
Steps to implement translator

1. import the original json file to be translated
2. if node object has states and time derivative then add 'dt' to the parameters of the node object and add 'time' as a stateful parameter
3. create functions for time_derivative expression for each state variable
4. Replace all names containing states into stateful_parameters
5. While evaluating the graph of the translated version, add the corresponding MDF functions

file location: src/modeci_mdf/full_translator.py
currently on branch 'stateful_parameter': https://github.com/ModECI/MDF/blob/stateful_parameter/src/modeci_mdf/full_translator.py

[pgleeson]

Translator code merged