Logical Operations Short-circuiting

Short-circuit is exhibited by logical expressions containing && (AND) and || (OR) operators.

In a logical expression involving the && operator, if the left-hand side expression evaluates to false, the overall expression also evaluates to false. In this case, the right-hand side expression is not evaluated because the outcome is already determined by the left-hand side expression.

Similarly, for a logical expression involving the || operator, if the left-hand side expression evaluates to true, the right-hand side expression is not evaluated because the outcome is determined by the left-hand side expression. This short-circuit evaluation of logical expressions helps you to optimize the execution by avoiding unnecessary evaluations when the result is already determined.

Short-circuiting Behavior for `Condition` and `MCDC` Objectives

Logical Operators and Logical Expressions for Condition and MCDC objectives can be considered short-circuiting or not when you analyze for dead logic or generate tests. The table summarizes different considerations:

Short-circuit consideration for Condition and MCDC objectives:

Modeling element	Short-circuit consideration for `Condition` and `MCDC` Objectives
Logic blocks (standalone/cascaded)	`Condition` and `MCDC` objectives are short-circuited only when `CovLogicBlockShortCircuit` is ON
Enabled subsystem	`Condition` and `MCDC` objectives are always non short-circuited.
Triggered subsystem	`Condition` and `MCDC` objectives are always non short-circuited.
Enabled and Triggered subsystem	`Condition` and `MCDC` objectives are always non short-circuited.
MATLAB^®, Stateflow^® (C or MATLAB as action language) and other Simulink^® Blocks (Fcn, If)	`Condition` and `MCDC` objectives always short-circuited

Short-circuiting Behavior for `Condition` Objectives

The table summarizes the difference between Condition objectives that depend on CovLogicBlockShortCircuit parameter:

Short-circuit considerations for Condition objectives based on CovLogicBlockShortCircuit parameter

Block	`Condition` Objective	Condition Expression when `CovLogicBlockShortCircuit` is ON	Condition Expression when `CovLogicBlockShortCircuit` is OFF
Logical `AND` block with 3 ports	`Condition` 'F', Port 2	(in1 && ~in2)	(~in2)
Logical `OR` block with 3 ports	`Condition` 'F', Port 2	(~in1 && ~in2)	(~in2)
MATLAB Function or Chart containing expression (u1 && u2 && u3)	'u2' `False`	(u1 && ~u2)	(u1 && ~u2)

Short-circuiting Behavior for `MCDC` Objectives

The table summarizes the difference in objectives that vary based on the CovLogicBlockShortCircuit parameter as shown:

Short-Circuit considerations for MCDC objectives based on CovLogicBlockShortCircuit parameter:

Block	`MCDC` Objective	`MCDC`Expression when `CovLogicBlockShortCircuit` is ON	`MCDC` Expression when `CovLogicBlockShortCircuit` is OFF
Logical `AND` block with 3 ports	expression for output with input port 2 `false`	(in1 && ~in2)	(in1 && ~in2 && in3)
Logical `AND` block with 3 ports	expression for output with input port 2 `true`	(in1 && in2 && in3)	(in1 && in2 && in3)
MATLAB Function or Chart containing expression (u1 && u2 && u3)	expression for output with input port 2 `false`	(in1 && ~in2)	(in1 && ~in2)
	expression for output with input port 2 `true`	(in1 && in2 && in3)	(in1 && in2 && in2)

Note

When MCDC expression is derived from a cascaded logic, it follows similar definition as logic blocks.

For more information, see "Short-Circuiting of Boolean Expressions for MCDC" in Analyzing MCDC for Cascaded Logic Blocks (Simulink Coverage).

Impact of `CovLogicBlockShortCircuit` parameter on `Condition` and `MCDC` Results

In some cases, coverage result for MCDC objectives can vary based on the CovLogicBlockShortCircuit parameter as shown:

When CovLogicBlockShortCircuit parameter is OFF, all the inputs are considered.

Short-Circuit considerations for Condition objectives based on CovLogicBlockShortCircuit parameter:

Block	`Condition` Objective	`Condition` Expression when `CovLogicBlockShortCircuit` is ON	`Condition` Expression when `CovLogicBlockShortCircuit` is OFF
Logical `AND` block with 3 ports	`Condition` 'F', Port 3	(in1 && in2 && ~in2) (Dead Logic)	(~in2) (Active Logic)

Short-Circuit considerations for MCDC objectives based on CovLogicBlockShortCircuit parameter:

Block	`MCDC` Objective	`MCDC`Expression when `CovLogicBlockShortCircuit` is ON	`MCDC` Expression when `CovLogicBlockShortCircuit` is OFF
Logical `AND` block with 3 ports	Expression for output with input port 2 `false`	(in1 && ~in2) (Active Logic)	(in1 && ~in2 && in2) (Dead Logic)