Logic Operations Short-Circuiting

Simulink^® Design Verifier™ considers logical operations and logical expressions as short-circuiting when analyzing for dead logic and when generating tests.

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 or MCDC Objectives

Modeling element	Short-Circuit consideration for Condition or MCDC Objectives
MATLAB®, Stateflow® (C/MATLAB) and other Simulink Blocks (Fcn, If)	Always short-circuited
Logic blocks (standalone/cascaded)	Short-circuited only when CovLogicBlockShortCircuit is ON

For Condition objective, consider the following simple logical operator example model. When CovLogicBlockShortCircuit parameter is ON, a previous input alone determines the block output, the analysis ignores any remaining block inputs. If the first input to a Logical Operator block whose Operator parameter specifies AND is false, the analysis ignores the values of the other inputs.

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

The tables summarizes the difference in objectives for short-circuit and non short-circuit case for Condition objective by using a similar logical expression for MATLAB function block:

Short-Circuit considerations for Condition objective

Condition ‘F’ Port 3	CovLogicBlockShortCircuit: ON	CovLogicBlockShortCircuit: OFF
Logical operator	(in1) && (in2) && (~in2) (dead logic)	~ in2 (active logic)
MATLAB Function with logical expression (in1 && in2 && in2)	(in1) && (in2) && (~in2) (dead logic)	(in1) && (in2) && (~in2) (dead logic)

For MCDC objective, along with the short-circuit mode, the CovMCDCMode or the coverage MCDC mode is set as a parameter.

The tables summarizes the difference in objectives for short-circuit and non short-circuit case for MCDC objective.

Short-Circuit considerations for MCDC objective

CovLogicBlockShortCircuit	CovMCDCMode	Standalone block	Cascaded Network
ON	Masking	Short circuited MCDC	MCDC for network (Short-circuited)
OFF	Masking	Non short-circuited MCDC	MCDC for network (Non short-circuited)
ON	Unique cause	Short-circuited MCDC	MCDC (Short-circuited) coverage result can differ from Simulink Design Verifier.
OFF	Unique cause	Non short-circuited MCDC	NA

Note

If covMCDCMode is Unique cause, then MCDC definition differs between coverage and MCDC.

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