Add highs backend (WIP)

.github/workflows/commit-ci.yml

@@ -34,6 +34,7 @@ jobs:
           -f requirements/dev.txt
           python=3.11
           coin-or-cbc
+          highspy
           gurobi::gurobi
         post-cleanup: all
         cache-environment: true

.github/workflows/pr-ci.yml

@@ -53,6 +53,7 @@ jobs:
           curl
           python=3.${{ matrix.py3version }}
           coin-or-cbc
+          highspy
           gurobi::gurobi
         post-cleanup: all
         cache-environment: true

src/calliope/backend/__init__.py

@@ -7,6 +7,7 @@
 from calliope.attrdict import AttrDict
 from calliope.backend.backend_model import BackendModel
 from calliope.backend.gurobi_backend_model import GurobiBackendModel
+from calliope.backend.highs_backend_model import HighsBackendModel
 from calliope.backend.latex_backend_model import (
     ALLOWED_MATH_FILE_FORMATS,
     LatexBackendModel,
@@ -37,5 +38,7 @@ def get_model_backend(
             return PyomoBackendModel(data, math, build_config)
         case "gurobi":
             return GurobiBackendModel(data, math, build_config)
+        case "highs":
+            return HighsBackendModel(data, math, build_config)
         case _:
             raise BackendError(f"Incorrect backend '{build_config.backend}' requested.")

src/calliope/backend/expression_parser.py

@@ -230,7 +230,7 @@ def _operate(
             case "*":
                 val = val * evaluated_operand
             case "/":
-                val = val / evaluated_operand
+                val = val * (1 / evaluated_operand)
             case "+":
                 val = val + evaluated_operand
             case "-":