Why Doesn't "clear all" Clear the Assumptions from the Symbolic Engine?

According to the doc page assumptions

• To clear all objects in the MATLAB workspace and close the Symbolic Math Toolbox™ engine associated with the MATLAB workspace resetting all its assumptions, use this command
• clear all

Comment: I think the doc page would be clearer if that clause replaced "resetting" with "clearing".

But

syms x
assume(x < 1)
assumptions
clear all
assumptions

I'm quite certain that in previous versions (like 2022a?) the command "clear all" did clear the assumptions from the engine.

Is this a relatively-newly-introduced bug or am I misremembering/misunderstanding the situation?

Answers is running 2024b, I see the same behavior on 2024a.

[Paul]

Apparently Answers is having an issue displyaing results from executed code (@Rena Berman, others have also noted this where everything looks fine while editing the post but the results disaappear when the post is submitted).

Here are the results from running the commands on my local system (R2024a)

>> syms x
>> assume(x < 1);
>> assumptions
 
ans =
 
x < 1
 
>> clear all
>> assumptions
 
ans =
 
x < 1
 

[Animesh]

Hey @Paul,

I tried running the same commands and it seems to work as expected for me:

[Paul]

@Animesh

Which version/update of Matlab? The results I showed are for R2024a Update 1. And I got the same result on Answers running R2024b.

[Animesh]

I'm using MATLAB R2024a, but I am encountering the issue in R2024b, as mentioned.

[Sam Chak]

Yes, @Paul. Tested in both. Thanks for pointing out the issue.

[Sam Chak]

At the moment, the workaround of dealing with the issue is to clear the assumptions using the 'assume()' command.

[Paul]

@Sam Chak

Which two specific versions did you test, by release AND update (both of your screenshots above are from 2024b)?

I'm asking because I see the problem in R2024a Update 1 on Windows, and here on Answers running R2024b, which doesn't show an Update number (is Update number no longer a thing in 2024b?).

ver

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MATLAB Version: 24.2.0.2729000 (R2024b)
MATLAB License Number: 40912989
Operating System: Linux 5.15.0-1062-aws #68~20.04.1-Ubuntu SMP Wed May 1 15:24:09 UTC 2024 x86_64
Java Version: Java 1.8.0_292-b10 with AdoptOpenJDK OpenJDK 64-Bit Server VM mixed mode
-------------------------------------------------------------------------------------------------
MATLAB                                                Version 24.2        (R2024b)
Simulink                                              Version 24.2        (R2024b)
5G Toolbox                                            Version 24.2        (R2024b)
Aerospace Blockset                                    Version 24.2        (R2024b)
Aerospace Toolbox                                     Version 24.2        (R2024b)
Antenna Toolbox                                       Version 24.2        (R2024b)
Audio Toolbox                                         Version 24.2        (R2024b)
Automated Driving Toolbox                             Version 24.2        (R2024b)
Bioinformatics Toolbox                                Version 24.2        (R2024b)
Bluetooth Toolbox                                     Version 24.2        (R2024b)
Communications Toolbox                                Version 24.2        (R2024b)
Computer Vision Toolbox                               Version 24.2        (R2024b)
Control System Toolbox                                Version 24.2        (R2024b)
Curve Fitting Toolbox                                 Version 24.2        (R2024b)
DO Qualification Kit                                  Version 24.2        (R2024b)
DSP System Toolbox                                    Version 24.2        (R2024b)
Database Toolbox                                      Version 24.2        (R2024b)
Datafeed Toolbox                                      Version 24.2        (R2024b)
Deep Learning Toolbox                                 Version 24.2        (R2024b)
Econometrics Toolbox                                  Version 24.2        (R2024b)
Embedded Coder                                        Version 24.2        (R2024b)
Filter Design HDL Coder                               Version 24.2        (R2024b)
Financial Instruments Toolbox                         Version 24.2        (R2024b)
Financial Toolbox                                     Version 24.2        (R2024b)
Fixed-Point Designer                                  Version 24.2        (R2024b)
Fuzzy Logic Toolbox                                   Version 24.2        (R2024b)
Global Optimization Toolbox                           Version 24.2        (R2024b)
HDL Coder                                             Version 24.2        (R2024b)
HDL Verifier                                          Version 24.2        (R2024b)
IEC Certification Kit                                 Version 24.2        (R2024b)
Image Acquisition Toolbox                             Version 24.2        (R2024b)
Image Processing Toolbox                              Version 24.2        (R2024b)
Industrial Communication Toolbox                      Version 24.2        (R2024b)
Instrument Control Toolbox                            Version 24.2        (R2024b)
LTE Toolbox                                           Version 24.2        (R2024b)
MATLAB Coder                                          Version 24.2        (R2024b)
MATLAB Compiler                                       Version 24.2        (R2024b)
MATLAB Compiler SDK                                   Version 24.2        (R2024b)
MATLAB Report Generator                               Version 24.2        (R2024b)
Mapping Toolbox                                       Version 24.2        (R2024b)
Medical Imaging Toolbox                               Version 24.2        (R2024b)
Mixed-Signal Blockset                                 Version 24.2        (R2024b)
Model Predictive Control Toolbox                      Version 24.2        (R2024b)
Model-Based Calibration Toolbox                       Version 24.2        (R2024b)
Navigation Toolbox                                    Version 24.2        (R2024b)
Optimization Toolbox                                  Version 24.2        (R2024b)
Parallel Computing Toolbox                            Version 24.2        (R2024b)
Partial Differential Equation Toolbox                 Version 24.2        (R2024b)
Phased Array System Toolbox                           Version 24.2        (R2024b)
Powertrain Blockset                                   Version 24.2        (R2024b)
Predictive Maintenance Toolbox                        Version 24.2        (R2024b)
RF Blockset                                           Version 24.2        (R2024b)
RF Toolbox                                            Version 24.2        (R2024b)
Radar Toolbox                                         Version 24.2        (R2024b)
Requirements Toolbox                                  Version 24.2        (R2024b)
Risk Management Toolbox                               Version 24.2        (R2024b)
Robotics System Toolbox                               Version 24.2        (R2024b)
Robust Control Toolbox                                Version 24.2        (R2024b)
Sensor Fusion and Tracking Toolbox                    Version 24.2        (R2024b)
SerDes Toolbox                                        Version 24.2        (R2024b)
Signal Processing Toolbox                             Version 24.2        (R2024b)
SimBiology                                            Version 24.2        (R2024b)
SimEvents                                             Version 24.2        (R2024b)
Simscape                                              Version 24.2        (R2024b)
Simscape Driveline                                    Version 24.2        (R2024b)
Simscape Electrical                                   Version 24.2        (R2024b)
Simscape Fluids                                       Version 24.2        (R2024b)
Simscape Multibody                                    Version 24.2        (R2024b)
Simulink 3D Animation                                 Version 24.2        (R2024b)
Simulink Check                                        Version 24.2        (R2024b)
Simulink Code Inspector                               Version 24.2        (R2024b)
Simulink Coder                                        Version 24.2        (R2024b)
Simulink Control Design                               Version 24.2        (R2024b)
Simulink Coverage                                     Version 24.2        (R2024b)
Simulink Design Optimization                          Version 24.2        (R2024b)
Simulink Design Verifier                              Version 24.2        (R2024b)
Simulink Desktop Real-Time                            Version 24.2        (R2024b)
Simulink PLC Coder                                    Version 24.2        (R2024b)
Simulink Real-Time                                    Version 24.2        (R2024b)
Simulink Report Generator                             Version 24.2        (R2024b)
Simulink Test                                         Version 24.2        (R2024b)
Stateflow                                             Version 24.2        (R2024b)
Statistics and Machine Learning Toolbox               Version 24.2        (R2024b)
Symbolic Math Toolbox                                 Version 24.2        (R2024b)
System Identification Toolbox                         Version 24.2        (R2024b)
Text Analytics Toolbox                                Version 24.2        (R2024b)
Vehicle Dynamics Blockset                             Version 24.2        (R2024b)
Vehicle Network Toolbox                               Version 24.2        (R2024b)
Vision HDL Toolbox                                    Version 24.2        (R2024b)
WLAN Toolbox                                          Version 24.2        (R2024b)
Wavelet Toolbox                                       Version 24.2        (R2024b)
Wireless HDL Toolbox                                  Version 24.2        (R2024b)

@Animesh reports the problem evident in R2024b, but NOT in 2024a, which would mean it was fixed in 2024a in an update after Update 1, but then the problem resurfaces in 2024b.

[Sam Chak]

Hi @Paul

The first screenshot was taken using Answers running R2024b. The second screenshot was taken using the basic version of MATLAB Online, which includes the Symbolic Math Toolbox. The "persistant assumptions after clear all" issue has not been filed in the Bug Reports. I hope MathWorks will address it in R2024b Update 1.

[Paul]

I filed a bug report. We'll see what happens ....

[Paul]

@Sam Chak

If you want to clear all of the assumptions as should happen with "clear all"

syms x y positive
assumptions
assume(assumptions,'clear')
assumptions

 
ans =
 
Empty sym: 1-by-0
 

[Paul]

Weird that in the preceding comment the output showed up for the second "assumptions" command but not the first .... hope MathWorks can sort out this issue soon (@Rena Berman)

[Rena Berman]

@Paul, I will forward this on.

[Tushal Desai]

FYI, we are investigating the issue in Answers where the symbolic outputs appear when editing but are not rendering when viewing the submitted post. I will post an update here when that is fixed in Answers.

[Sam Chak]

Thank you, @Paul, on the method for clearing all of the assumptions. Also thank @Rena Berman and @Tushal Desai for their attention to this matter.

[Paul]

Tech Support confirmed that this behavior is an "issue" (is that different than a bug?) and may consider fixing it in a future release. I do realize they have reasons to not be concrete about it. Nevertheless, anyone with code that relies on the as-documented, as-previously-implemented behavior might be in for a surprise.

[Sam Chak]

Thanks @Paul. I put a link to

Clear Assumptions and Reset the Symbolic Engine