feat: add initial support for XMILE/Stella models by chrispcampbell · Pull Request #778 · climateinteractive/SDEverywhere

chrispcampbell · 2026-02-13T19:42:42Z

Fixes #468

@ToddFincannonEI: Sorry for the large PR. I could've broken it up into 3 PRs but figured it would be better for you to see how it all fits together. I recommend first reading the issue comment that I just posted for context. I will annotate files and code in the PR to help provide more context.

The main thing is that none of this should have an impact on your/our existing models.

I'm cc'ing @bobeberlein mainly as a heads up. Bob, you're welcome to review parts and provide feedback if you'd like, but it's not critical since I know the code base is unfamiliar, and you're also welcome to ignore this completely 😄

…f change

…kind from file extension

…ions and read-subscripts tests

…ackage

…tmx model

…with shorthand

…ed variable is non-apply-to-all

… from sample models

…ons differently

…nition

…r files

[skip ci]

… and XMILE/Stella function names

… a function call or more complex expression

…nces of "mdl" to "model"

…ddition to Vensim files

… before comparing

…subscripts)

Map XMILE/Stella's SAFEDIV function to the equivalent Vensim ZIDZ function. SAFEDIV performs safe division, returning 0 when the denominator is zero. Generated with Claude Code

Map XMILE/Stella's DELAY function to the equivalent Vensim DELAY FIXED function. DELAY is a fixed-delay function that outputs a past value of the input after a specified delay time. Generated with Claude Code

Map XMILE/Stella's SIZE function to the equivalent Vensim ELMCOUNT function. SIZE returns the number of elements in a dimension at compile time. Generated with Claude Code

…E models - Add _DEPRECIATE_STRAIGHTLINE case to validateStellaFunctionCall() - Add _ACTIVE_INITIAL case to validateStellaFunctionCall() - Update parse-xmile-variable-def.ts to synthesize ACTIVE_INITIAL calls - Add tests for both functions - Add PLAN.md documenting XMILE integration test analysis 7 of 11 XMILE integration tests now pass. Generated with Claude Code

chrispcampbell

I added some comments to help add context for review.

chrispcampbell · 2026-02-13T19:46:18Z

packages/cli/src/sde-test.js

    choices: ['js', 'c'],
    default: 'js'
  },
+  tooldat: {


I added this option for sde test so that we can pass a custom name for the dat file. Before this, it assumed that the file is called {model}.dat.

I could've also updated sde test to support reading csv files in addition to dat, but I didn't want to go deep on something that's probably not used much outside of our own testing framework. So instead I just added some code to our test scripts to convert the csv files (for expected Stella results) to dat format as part of the testing process.

chrispcampbell · 2026-02-13T19:48:43Z

packages/cli/src/utils.js


 /**
- * Normalize a model pathname that may or may not include the .mdl extension.
+ * Normalize a model pathname that may or may not include the .mdl or .xmile/.stmx/.itmx extension.


The sde CLI commands previously automatically found the corresponding mdl file for a given model name. Now we do the same thing for xmile/stmx/itmx files. If there are multiple options, it throws an error and the user can specify which one by providing a full file name with extension.

chrispcampbell · 2026-02-13T19:50:47Z

packages/compile/src/generate/gen-code-c-from-vensim.spec.ts

The existing code gen tests were written using Vensim format as the input model format, but we need new tests that cover similar things except for XMILE format (since the code gen can be different in certain cases), so I renamed these files accordingly.

chrispcampbell · 2026-02-13T19:53:34Z

packages/compile/src/generate/gen-expr.js

    //
    //

+    // Simple functions that are common to Vensim and XMILE/Stella


I changed this big switch statement so that it's more clear which cases are for both Vensim+XMILE, and which cases are for Vensim only or XMILE/Stella only.

And I added comments to note any format-specific things.

chrispcampbell · 2026-02-13T19:56:42Z

packages/compile/src/model/read-equations-vensim.spec.ts

 }

-describe('readEquations', () => {
+describe('readEquations (from Vensim model)', () => {


I renamed this file to make it focused on reading equations in Vensim format. There is a new copy of these tests focused on reading equations in XMILE format.

I added one new test here to align with a test that I added in the XMILE tests.

chrispcampbell · 2026-02-13T20:00:59Z

packages/create/src/index.ts

I updated the create package so that it handles stmx files in the same way that we already handled mdl files.

chrispcampbell · 2026-02-13T20:02:41Z

packages/parse/src/ast/ast-types.ts


 /** A complete model definition, including all defined dimensions and equations. */
 export interface Model {
+  /**


This was the only addition I made at the AST level. We needed a way to include the simulation parameters because (unlike Vensim) they're in a different part of the XMILE structure than the equations.

chrispcampbell · 2026-02-13T20:05:57Z

packages/parse/src/xmile/parse-xmile-model.spec.ts

For the record, I wrote nearly all of the test code in this PR myself, but really wish Claude was around when I was first working on this since the tests are very tedious to write. (I started this long before AI tools were a daily use kind of thing.) We could get even better test coverage by letting Claude have at it, but I'll save that for another day.

chrispcampbell · 2026-02-13T20:07:04Z

tests/modeltests


+    if [[ $INPUT_FORMAT == "stmx" ]]; then
+      # Skip tests for models that are not yet supported by the Stella/XMILE backend
+      if [[ $m == "allocate" || $m == "arrays" ]]; then


As noted in my issue comment, we are skipping these two tests because they are failing (only in part). I filed separate issues to address these separately.

chrispcampbell · 2026-02-13T20:09:32Z

packages/parse/package.json

    "ci:build": "run-s clean lint prettier:check type-check test:ci build docs"
  },
  "dependencies": {
+    "@rgrove/parse-xml": "^4.1.0",


We have one new dependency in the parse package, which is not used in the case of Vensim models. The good news is that the parse-xml package is pretty minimal and has no dependencies of its own.

travisfranck · 2026-02-13T21:49:55Z

I'm excited by this PR! Likely using Stella for our next project, so hopefully we can use SDE too! Thank you in advance, Chris.

chrispcampbell added 30 commits April 24, 2024 13:51

feat: add initial XMILE parsing support

fed74ce

fix: update XMILE parser to account for SubscriptRange -> DimensionDe…

0ab29b4

…f change

fix: checkpoint work on parsing gf elements

180e87a

fix: flesh out parsing of gf elements

5182e02

fix: expose xmile parsing functions in index

2c21f75

Merge branch 'main' into chris/468-xmile

6436b97

fix: update XMILE code in parse package to use new canonicalId function

b0343a1

fix: add initial support for parsing XMILE models in compile package

89b98d2

Merge branch 'main' into chris/468-xmile

6916d5f

test: add initial support for testing stmx files

d7c15c0

fix: update cli package to accept stmx and xmile files + infer model …

22cb090

…kind from file extension

test: add helper function for generating XMILE content

a56e839

test: create separate files for vensim and xmile paths for read-equat…

bff3837

…ions and read-subscripts tests

fix: add temporary workaround for XMILE dimension wildcard in parse p…

a56cb1a

…ackage

test: restore comment in test

feefb1f

fix: update compile package to handle XMILE wildcards

7ffe1f6

test: update test expectations to account for differences in arrays.s…

90c2051

…tmx model

test: add separate tests for non-apply-to-all with separate defs and …

b42ab63

…with shorthand

fix: correct handling of wildcards to work in the case where referenc…

48532e3

…ed variable is non-apply-to-all

test: convert a batch of readEquations tests to verify XMILE

8ef4605

test: convert a batch of readEquations tests for XMILE

2032ae5

test: convert the last batch and remove all remaining tests that read…

8227ded

… from sample models

fix: update readEquations so that it handles Vensim and Stella functi…

3a26509

…ons differently

fix: convert XMILE logical operators to Vensim syntax before parsing

7748cb9

docs: fix comment

3f797c3

fix: restore handling of INTEG function calls and update tests

2c8ca56

fix: include itmx as one of the supported xmile file extensions

c7d9744

fix: update XMILE parser to ignore non_negative elements in stocks

4f384bd

fix: improve error message when parsing fails for XMILE variable defi…

0033fca

…nition

fix: include line number from original XML input in XMILE parsing errors

fe73b21

chrispcampbell added 27 commits September 5, 2025 11:32

test: remove tests for subscripted variables that are covered in othe…

425552f

…r files

test: remove tests for functions not supported in XMILE/Stella

a0a0c04

test: convert tests for subscripted equations

2968846

test: convert tests for supported XMILE/Stella functions

b65e528

[skip ci]

fix: update generateFunctionCall to handle differences between Vensim…

7d00640

… and XMILE/Stella function names

fix: update IF THEN ELSE parsing to handle case where it is nested in…

f7bd6b5

… a function call or more complex expression

fix: improve indentation in xmile function

bd8cb56

fix: update create package to support XMILE file types + change insta…

cf8f063

…nces of "mdl" to "model"

test: update step-config tests to verify handling of XMILE files in a…

f24f43f

…ddition to Vensim files

Merge branch 'main' into chris/468-xmile

29b37f6

build: update lock file

47be15a

fix: add tooldat option for sde test command

0da1d4f

test: update modeltests script to convert Stella-generated CSV to DAT…

af199ba

… before comparing

test: disable lint warnings for use of any in tests

7e4aa61

fix: use canonicalVarId instead of canonicalId (which doesn't handle …

f28013f

…subscripts)

feat: add SAFEDIV function support for XMILE models

940d069

Map XMILE/Stella's SAFEDIV function to the equivalent Vensim ZIDZ function. SAFEDIV performs safe division, returning 0 when the denominator is zero. Generated with Claude Code

feat: add DELAY function support for XMILE models

631cb38

Map XMILE/Stella's DELAY function to the equivalent Vensim DELAY FIXED function. DELAY is a fixed-delay function that outputs a past value of the input after a specified delay time. Generated with Claude Code

feat: add SIZE function support for XMILE models

5099835

Map XMILE/Stella's SIZE function to the equivalent Vensim ELMCOUNT function. SIZE returns the number of elements in a dimension at compile time. Generated with Claude Code

docs: update comments

e325d66

Merge branch 'main' into chris/468-xmile

be3038d

docs: update comment

34bf1d9

docs: update PLAN.md to account for latest test fixes

653bb3f

test: skip two test models that are not yet supported by XMILE backend

546d07f

fix: prettier

034ed4d

fix: update copyright years in parse package

ff27a52

docs: remove PLAN.md (I added this to an issue comment for the record)

dc97cca

chrispcampbell requested a review from ToddFincannonEI February 13, 2026 19:42

chrispcampbell commented Feb 13, 2026

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feat: add initial support for XMILE/Stella models#778

feat: add initial support for XMILE/Stella models#778
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