ashow

Identify and highlight algebraic loops in simulation debugging session

Syntax

ashow

ashow blk

ashow aloop

ashow clear

Description

ashow displays in the MATLAB^® Command Window a list of algebraic loops in the model for the current simulation debugging session.

You can use this function in a simulation debugging session started:

• Interactively, using the Simulink^® Toolstrip

• Programmatically, using the sldebug function

• Programmatically, using the sim function with the 'debug' name-value argument

Note

This function is available only for simulation debugging sessions started programmatically and for interactive simulation debugging sessions while paused within a time step.

ashow blk displays in the MATLAB Command Window information about the algebraic loop that contains the block blk. When the block blk is part of an algebraic loop, this command also highlights the algebraic loop that contains the block blk in the block diagram.

ashow aloop displays in the MATLAB Command Window information about the algebraic loop aloop and highlights the algebraic loop in the block diagram.

ashow clear removes algebraic loop highlighting from the block diagram.

Examples

Examine Algebraic Loops in Simulation Debugging Session

Use the ashow function to examine algebraic loops in the model sldemo_hydcyl.

Open the model sldemo_hydcyl.

openExample("simulink_general/sldemo_hydcylExample",...
    supportingFile="sldemo_hydcyl.slx")

Start a simulation debugging session for the model using the sldebug function. The MATLAB Command Prompt (>>) becomes the Simulink debugger prompt ((sldebug @0): >> ).

sldebug sldemo_hydcyl

(sldebug @0): >> 

Use the step function to step to the first method in the first major time step for the simulation.

step top

%----------------------------------------------------------------%
[TM = 0                      ] sldemo_hydcyl.Outputs.Major

Use the ashow function to show a list of algebraic loops in the model.

ashow

Found 1 Algebraic loop(s): 
System number#Algebraic loop id, number of blocks in loop
- (0)0#1, 9 block(s) in loop

Use the algebraic loop identifier in the information returned by the ashow function to get more information about the algebraic loop. The ashow function lists the paths to the nine blocks in the loop and identifies which blocks correspond to algebraic variables in the loop.

ashow (0)0#1

- sldemo_hydcyl/Valve//Cylinder//Piston//Spring Assembly/Control Valve Flow/IC
- sldemo_hydcyl/Valve//Cylinder//Piston//Spring Assembly/Control Valve Flow/Sqrt
- sldemo_hydcyl/Valve//Cylinder//Piston//Spring Assembly/Control Valve Flow/Product
- sldemo_hydcyl/Valve//Cylinder//Piston//Spring Assembly/laminar flow pressure drop
- sldemo_hydcyl/Valve//Cylinder//Piston//Spring Assembly/Sum7
- sldemo_hydcyl/Pump/IC
- sldemo_hydcyl/Valve//Cylinder//Piston//Spring Assembly/Control Valve Flow/Sum1 (algebraic variable)
- sldemo_hydcyl/Pump/Sum1
- sldemo_hydcyl/Pump/leakage (algebraic variable)

The ashow function also highlights the specified loop in the block diagram. In this model, the loop includes blocks in two different levels of the model hierarchy, so only the blocks in the Control Valve Flow masked subsystem are visible.

When you have finished analyzing and debugging the model, use the stop function to end the simulation debugging session.

stop

Input Arguments

blk — Block in model

(t)s:b | gcb

Block in model, specified as one of these options:

• gcb — Current block

• (t)s:b — Block ID, where t is the index of the task that contains the block, s is the index of the system that contains the block, and b is the block index

.

aloop — Algebraic loop

algebraic loop ID

Algebraic loop, specified as an algebraic loop ID. Algebraic loop IDs have the form (t)s#n, where t is the index of the task that contains the algebraic loop, s is the index of the system that contains the algebraic loop, and n is the index of the algebraic loop in the system.

Tips

To start a simulation debugging session interactively, add one or more breakpoints to your model, and in the Breakpoints List, check that Pause within time step is selected. When the simulation pauses on a breakpoint, some of the programmatic debugging commands, such as the stop command, are available for use in the MATLAB Command Window.

Version History

Introduced before R2006a

R2024a: sldebug prompt in MATLAB Command Window indicates when simulation debugging session is paused within time step

When you start a simulation debugging session using the Simulink Editor, you can issue some programmatic simulation debugging commands, such as probe or stop, while the simulation is paused within a time step. The sldebug command prompt (sldebug>>) now replaces the MATLAB command prompt (>>) to indicate in the MATLAB Command Window when the simulation is paused within a time step. As in prior releases, you can issue both MATLAB commands and the supported simulation debugging commands at the sldebug command prompt.

For more information, see Simulink Debugging Programmatic Interface.