Diagnostics tool for ill-posed constraints (#1454)

* Working on cancellation detection

* Fixing typo

* Improving efficiency

* More efficiency and testing

* Reducing duplicated code in tests

* Finishing testing

* Adding additioanl tests and clean up

* Running pylint

* Adding constraint walker to diagnostics toolbox

* Addressing simple review comments

* Accumulate node rather than str(node)

* Clean up some tests

* Supporting ranged expressions

* Apply suggestions from code review

* Regorganising and fixing pylint issues

* Fixing false positives for linking constraints

* Fixing unused variable warning

* Fixing bug related to external functions with string arguments

* Addressing comments

* removing debugging prints

* Addressing more comments

* Debugging issue with nested external functions

* Adding todo

* Relax test tolerance due to Windows failures

* Adding catches for string arguments/values

* Test for nested external functions

* Fixing bug in walker logic for string arguments to external funcitons

* Address double counting of constraints

* Fixing typo

* Bumping Pyomo version

* Adding zero tolerance

* Adding test for zero tolerance

* Fixing typo

* Logic to skip scaled equality constraints

* Handling mole fraction type constraints

* Catching negations

* Fixing typos

* Limit of cancelling combinations

* Fixing typos

* Displaying cancelling terms to user

* More detail of mismatches

* Adding hooks and warnings about new config arguments

* Expression aware to string method

* Moving expression writer to util/misc

* Typos and comments

* Using StrEnum

idaes/core/scaling/custom_scaler_base.py

@@ -16,7 +16,6 @@
 Author: Andrew Lee
 """
 from copy import copy
-from enum import Enum
 
 from pyomo.environ import ComponentMap, units, value
 from pyomo.core.base.units_container import UnitsError
@@ -26,6 +25,7 @@
 from idaes.core.scaling.scaling_base import CONFIG, ScalerBase
 from idaes.core.scaling.util import get_scaling_factor, NominalValueExtractionVisitor
 import idaes.logger as idaeslog
+from idaes.core.util.misc import StrEnum
 
 # Set up logger
 _log = idaeslog.getLogger(__name__)
@@ -41,7 +41,7 @@
 }
 
 
-class ConstraintScalingScheme(str, Enum):
+class ConstraintScalingScheme(StrEnum):
     """
     Schemes available for calculating constraint scaling factors.
 

idaes/core/util/misc.py

@@ -15,9 +15,12 @@
 This module contains miscellaneous utility functions for use in IDAES models.
 """
 from enum import Enum
+import sys
 
 import pyomo.environ as pyo
 from pyomo.common.config import ConfigBlock
+from pyomo.core.expr.visitor import _ToStringVisitor
+from pyomo.core.base.expression import ExpressionData
 
 import idaes.logger as idaeslog
 
@@ -177,3 +180,66 @@ class StrEnum(str, Enum):
 
     def __str__(self):
         return str(self.value)
+
+
+class _ToExprStringVisitor(_ToStringVisitor):
+    """
+    Derived version of the Pyomo _ToStringVisitor class
+    which checks for named Expressions in the expression tree
+    and prints their name instead of expanding the expression tree.
+    """
+
+    def visiting_potential_leaf(self, node):
+        # Check if node is a named Expression
+        if isinstance(node, ExpressionData):
+            # If it is, return the name of the Expression
+            return True, node.name
+
+        # Otherwise, continue descending as normal
+        return super().visiting_potential_leaf(node)
+
+
+def compact_expression_to_string(expr):
+    """Return a compact string representation of an expression.
+
+    Unlike the normal Pyomo string representations, this function will
+    identify any Expressions that appear within the expression tree and
+    print the name of these rather than expanding the expression tree.
+
+    Args:
+        expr: ExpressionBase. The root node of an expression tree.
+
+    Returns:
+        A string representation for the expression.
+    """
+    # Create and execute the visitor pattern
+    #
+    visitor = _ToExprStringVisitor(verbose=False, smap=None)
+    return visitor.dfs_postorder_stack(expr)
+
+
+def print_compact_form(expr, stream=None):
+    """
+    Writes a compact string representation of the given component or
+    expression to the specified stream.
+
+    Unlike the normal Pyomo string representations, this function will
+    identify any Expressions that appear within the expression tree and
+    print the name of these rather than expanding the expression tree.
+
+    Args:
+        expr: component or expression to print
+        stream: StringIO object to write to. Default is stdout.
+
+    Returns:
+        None
+    """
+    if stream is None:
+        stream = sys.stdout
+
+    if hasattr(expr, "expr"):
+        # We have a Constraint or Expression
+        # We want to print the expression, not the object name
+        expr = expr.expr
+
+    stream.write(compact_expression_to_string(expr))