I have been trying to branch out of computer science/software and learn more about how things are made in the “real world”. Here are some videos that I have watched as part of an online intro to manufacturing course I’m slowly working through. The key idea in the first video is that not everybody needs to get a 4-year degree. Don’t overlook manufacturing when picking a career path.
Path To Careers – The Truth About Manufacturing Careers
The Path to Careers video above features people from these companies:
The “future of manufacturing” video below might be a bit dated now. I’m not sure how many of its predictions hold as of today.
The Future of Manufacturing
There is also a discussion of the services industry in manufacturing, which is great because it really opens my eyes to how I’ve never really thought much about this sector.
The Evolution of Manufacturing Services Industry
Another video to stimulate some thinking about supply chains:
What Toilet Paper Can Teach Us About Supply Chains | Willy Shih | TEDxBeaconStreet
To build and run the JMH benchmark, ensure Maven is installed (the mvn command should be available in the shell). On Ubuntu, this is as easy as running sudo apt install maven then setting up JMH using the steps below.
git clone https://github.com/swesonga/benchmarks
cd benchmarks
cd java/jmh
./setup_jmh_jdk_micros.sh
./run_jmh_jdk_micros.sh Parallel 1 2 10 5 5
The setup_jmh_jdk_micros.sh script builds the JMH JDK microbenchmarks and the run_jmh_jdk_micros.sh run the benchmark. Someone recently asked why there are 2 java processes shown in top when the run_jmh_jdk_micros.sh script runs given that it launches only 1 java process. I learned from this site how to use top to see java processes only: run top, type ‘o’, then type ‘COMMAND=java’ and press ENTER. This is the resulting output from the top command:
top - 22:15:21 up 8:15, 1 user, load average: 1.73, 0.66, 0.30
Tasks: 330 total, 1 running, 329 sleeping, 0 stopped, 0 zombie
%Cpu(s): 20.9 us, 0.6 sy, 0.0 ni, 78.3 id, 0.0 wa, 0.0 hi, 0.2 si, 0.0 st
MiB Mem : 15415.5 total, 5837.9 free, 5436.0 used, 4141.6 buff/cache
MiB Swap: 2048.0 total, 2048.0 free, 0.0 used. 9568.6 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
22007 saint 20 0 5009436 1.1g 22464 S 345.3 7.2 1:02.74 java
21927 saint 20 0 5607592 1.1g 23100 S 0.3 7.2 0:01.08 java
Sure enough, there are 2 java processes, each with 1.1g RES. This can also be confirmed by running the ps -aux | grep java command.
Notice that one of the processes has an IP address and what is most likely a port number. Without knowing anything else, this would suggest a client/server model in use. To better understand why there are 2 java processes, let us see look at how the run script launches Java. It passes flags like -f 1 to the benchmark jar file. What parses these flags?
The benchmark JAR file is created from a pom.xml file containing a mainClass attribute of org.openjdk.jmh.Main. That’s the class responsible for parsing these flags. This Main class uses the CommandLineOptions class to parse arguments like -f 1 then executes the Runner.run() method. Runner.runBenchmarks() checks whether the benchmarks should be run embedded or forked. runBenchmarksEmbedded() has a warning about using non-forked runs only for debugging purposes. This answers the question of why there are 2 JVMs: we are running in forked mode. runSeparate() has a getForkedMainCommand() method, which suggests that there is most likely a way to pass custom arguments to the ForkedMain JVM.
Now that we understand why there are 2 JVMs, can we control the heap size of each of them independently? The CommandLineOptions class has a list of all the supported arguments. Notice the jvmArgs, jvmArgsAppend, and jvmArgsAppend arguments! These suggest that we can indeed control the heap sizes of each of the JVMs. Use the jvmArgsAppend flag in the run_jmh_jdk_micros.sh script (e.g. just before the benchmark_filter_regex to specify a custom heap size for the forked java process (independent of the jvm_heap_size_opts).
Installing Maven
I did not have Java set up on my Ubuntu VM. Therefore, setting up MVN installed Java and many other dependencies. I decided to list these here for future reference.
saint@vm1ubuntu:~/java$ sudo apt install maven
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following additional packages will be installed:
ca-certificates-java default-jre-headless java-common libaopalliance-java libapache-pom-java libatinject-jsr330-api-java libcdi-api-java libcommons-cli-java
libcommons-io-java libcommons-lang3-java libcommons-parent-java libgeronimo-annotation-1.3-spec-java libgeronimo-interceptor-3.0-spec-java libguava-java
libguice-java libhawtjni-runtime-java libjansi-java libjansi-native-java libjsr305-java libmaven-parent-java libmaven-resolver-java libmaven-shared-utils-java
libmaven3-core-java libplexus-cipher-java libplexus-classworlds-java libplexus-component-annotations-java libplexus-interpolation-java libplexus-sec-dispatcher-java
libplexus-utils2-java libsisu-inject-java libsisu-plexus-java libslf4j-java libwagon-file-java libwagon-http-shaded-java libwagon-provider-api-java
openjdk-11-jre-headless
Suggested packages:
default-jre libaopalliance-java-doc libatinject-jsr330-api-java-doc libel-api-java libcommons-io-java-doc libcommons-lang3-java-doc libasm-java libcglib-java
libjsr305-java-doc libmaven-shared-utils-java-doc liblogback-java libplexus-classworlds-java-doc libplexus-sec-dispatcher-java-doc libplexus-utils2-java-doc junit4
testng libcommons-logging-java liblog4j1.2-java fonts-dejavu-extra fonts-ipafont-gothic fonts-ipafont-mincho fonts-wqy-microhei | fonts-wqy-zenhei
The following NEW packages will be installed:
ca-certificates-java default-jre-headless java-common libaopalliance-java libapache-pom-java libatinject-jsr330-api-java libcdi-api-java libcommons-cli-java
libcommons-io-java libcommons-lang3-java libcommons-parent-java libgeronimo-annotation-1.3-spec-java libgeronimo-interceptor-3.0-spec-java libguava-java
libguice-java libhawtjni-runtime-java libjansi-java libjansi-native-java libjsr305-java libmaven-parent-java libmaven-resolver-java libmaven-shared-utils-java
libmaven3-core-java libplexus-cipher-java libplexus-classworlds-java libplexus-component-annotations-java libplexus-interpolation-java libplexus-sec-dispatcher-java
libplexus-utils2-java libsisu-inject-java libsisu-plexus-java libslf4j-java libwagon-file-java libwagon-http-shaded-java libwagon-provider-api-java maven
openjdk-11-jre-headless
0 upgraded, 37 newly installed, 0 to remove and 72 not upgraded.
Need to get 52.7 MB of archives.
After this operation, 189 MB of additional disk space will be used.
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The build_llvm_release.bat script in the LLVM repo is used to create a release build for Windows. Running it without any arguments displays a sample command line to use to build LLVM.
cd \repos && mkdir llvmcd \repos\llvm\llvm-project\llvm\utils\release
C:\> cd \repos\llvm\llvm-project\llvm\utils\release
C:\repos\llvm\llvm-project\llvm\utils\release> build_llvm_release.bat
--version option is required
=============================
Script for building the LLVM installer on Windows,
used for the releases at https://github.com/llvm/llvm-project/releases
Usage: build_llvm_release.bat --version <version> [--x86,--x64, --arm64]
Options:
--version: [required] version to build
--help: display this help
--x86: build and test x86 variant
--x64: build and test x64 variant
--arm64: build and test arm64 variant
Note: At least one variant to build is required.
Example: build_llvm_release.bat --version 15.0.0 --x86 --x64
Let us build version 17.0.1, which is the latest LLVM release. Open an administrator Developer Command Prompt then run:
:: set PATH=%PATH%;C:\Program Files\7-Zip
build_llvm_release.bat --version 17.0.1 --x64
The first error is caused by mv not being a standard command in the Windows command prompt. There are ways to create aliases, e.g. alias – Aliases in Windows command prompt – Stack Overflow but given that this is a batch file, why not just use the built-in function? I fix this in the script.
C:\repos\llvm\llvm-project\llvm\utils\release\llvm_package_17.0.1> mv llvm-project-* llvm-project || exit /b 1
'mv' is not recognized as an internal or external command,
operable program or batch file.
The build directory needs to be deleted before restarting the build with the fix. Otherwise, the script will fail.
However, from a new command window, it looks like it hasn’t been set up.
C:\repos> python --version
Python was not found; run without arguments to install from the Microsoft Store, or disable this shortcut from Settings > Manage App Execution Aliases.
Just running python loads the Microsoft Store:
I proceed with the Customize Installation option in the open Python installer, this time selecting “for all users (requires admin privileges)”.
I’m not sure why the “Install Python 3.11 for all users” option is not checked on the “Advanced Options” page.
Opening a new command prompt then running python still gives the same behavior as before. where python shows that the new installation appears 2nd.
C:\repos> where python
C:\Users\saint\AppData\Local\Microsoft\WindowsApps\python.exe
C:\Python311\python.exe
The PATH environment variable has these paths in reverse order so I don’t understand what is happening. Looks like the easiest way forward is to just install python from the Microsoft Store – this at least ensures that python scripts can run. After a failure due to the python command not being found, closer inspection of build_llvm_release.bat reveals that it needs the PYTHON_HOME environment variable to be set. However, that is set on line 358 using the python_dir variable, which is in turn the first argument to :set_environment. The call to set_environment is from :do_build_32 (or do_build_64), which uses a hard-coded python path! The script should first validate the python installation and exit early if it cannot be found! I should have reported/fixed these when I worked on Tracking Down Missing Headers in LLVM for Windows – Saint’s Log (swesonga.org) last year.
Build Errors
With the Python path fixed, the build proceeds but the C++ compilation fails. A few months ago I got the error below build version 15.0.7. Unfortunately, I didn’t explicitly note the compiler version.
FAILED: tools/clang/lib/Analysis/FlowSensitive/CMakeFiles/obj.clangAnalysisFlowSensitive.dir/HTMLLogger.cpp.obj
C:\PROGRA~1\MICROS~3\2022\COMMUN~1\VC\Tools\MSVC\1438~1.331\bin\Hostx64\x64\cl.exe /nologo /TP ... -c C:\repos\llvm\llvm-project\llvm\utils\release\llvm_package_17.0.1\llvm-project\clang\lib\Analysis\FlowSensitive\HTMLLogger.cpp
C:\repos\llvm\llvm-project\llvm\utils\release\llvm_package_17.0.1\llvm-project\clang\lib\Analysis\FlowSensitive\HTMLLogger.cpp(332): fatal error C1001: Internal compiler error.
(compiler file 'msc1.cpp', line 1587)
To work around this problem, try simplifying or changing the program near the locations listed above.
If possible please provide a repro here: https://developercommunity.visualstudio.com
Please choose the Technical Support command on the Visual C++
Help menu, or open the Technical Support help file for more information
Additional troubleshooting is obviously required to make progress here. I might try to create a narrowed down testcase for the internal compiler error or perhaps just report it as is and let the Visual C++ team figure that out.
Note: I wrote this in October 2022 but never got around to posting it. Doing so now to enable comparisons with the latest sources and compilers.
In Failing to Build Flang with Visual C++, the C++ compiler had bugs that prevented compilation from succeeding. I just tried a new version of the Visual C++ compiler (Microsoft (R) C/C++ Optimizing Compiler Version 19.34.31823.3 for x64). This failed to build the same commit with the following error.
D:\dev\repos\llvm-project\flang\lib\Evaluate\fold-implementation.h(1585): error C2220: the following warning is treated as an error
D:\dev\repos\llvm-project\flang\lib\Evaluate\fold-implementation.h(1585): warning C4189: 'ctx': local variable is initialized but not referenced
...
D:\dev\repos\llvm-project\flang\lib\Evaluate\fold-implementation.h(1578): error C2220: the following warning is treated as an error
D:\dev\repos\llvm-project\flang\lib\Evaluate\fold-implementation.h(1578): warning C4101: 'buffer': unreferenced local variable
...
Moving that variable deeper into the if-statement addresses that issue. I end up having to suppress C4661 again.
D:\dev\repos\llvm-project\flang\include\flang\Evaluate\expression.h(101): error C2220: the following warning is treated as an error
D:\dev\repos\llvm-project\flang\include\flang\Evaluate\expression.h(101): warning C4661: 'std::optional<Fortran::evaluate::DynamicType> Fortran::evaluate::ExpressionBase<Fortran::evaluate::SomeDerived>::GetType(void) const': no suitable definition provided for explicit template instantiation request
...
C:\PROGRA~1\MIB055~1\2022\Preview\VC\Tools\MSVC\1434~1.318\bin\Hostx64\x64\cl.exe /nologo /TP -DFLANG_LITTLE_ENDIAN=1 -DUNICODE -D_CRT_NONSTDC_NO_DEPRECATE -D_CRT_NONSTDC_NO_WARNINGS -D_CRT_SECURE_NO_DEPRECATE -D_CRT_SECURE_NO_WARNINGS -D_SCL_SECURE_NO_DEPRECATE -D_SCL_SECURE_NO_WARNINGS -D_UNICODE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -ID:\dev\repos\llvm-project\build-nowarn\tools\flang\unittests\Evaluate -ID:\dev\repos\llvm-project\flang\unittests\Evaluate -ID:\dev\repos\llvm-project\flang\include -ID:\dev\repos\llvm-project\build-nowarn\tools\flang\include -ID:\dev\repos\llvm-project\build-nowarn\include -ID:\dev\repos\llvm-project\llvm\include -external:ID:\dev\repos\llvm-project\llvm\..\mlir\include -external:ID:\dev\repos\llvm-project\build-nowarn\tools\mlir\include -external:ID:\dev\repos\llvm-project\build-nowarn\tools\clang\include -external:ID:\dev\repos\llvm-project\llvm\..\clang\include -external:W0 /DWIN32 /D_WINDOWS /Zc:inline /Zc:__cplusplus /Oi /bigobj /permissive- /W4 -wd4141 -wd4146 -wd4244 -wd4267 -wd4291 -wd4351 -wd4456 -wd4457 -wd4458 -wd4459 -wd4503 -wd4624 -wd4722 -wd4100 -wd4127 -wd4512 -wd4505 -wd4610 -wd4510 -wd4702 -wd4245 -wd4706 -wd4310 -wd4701 -wd4703 -wd4389 -wd4611 -wd4805 -wd4204 -wd4577 -wd4091 -wd4592 -wd4319 -wd4709 -wd4661 -wd4927 -wd4324 -w14062 -we4238 /Gw /WX /MD /O2 /Ob2 -UNDEBUG -std:c++17 /showIncludes /Fotools\flang\unittests\Evaluate\CMakeFiles\FortranEvaluateTesting.dir\fp-testing.cpp.obj /Fdtools\flang\unittests\Evaluate\CMakeFiles\FortranEvaluateTesting.dir\FortranEvaluateTesting.pdb /FS -c D:\dev\repos\llvm-project\flang\unittests\Evaluate\fp-testing.cpp
C:\Program Files\Microsoft Visual Studio\2022\Preview\VC\Tools\MSVC\14.34.31823\include\xtree(1664): error C2220: the following warning is treated as an error
C:\Program Files\Microsoft Visual Studio\2022\Preview\VC\Tools\MSVC\14.34.31823\include\xtree(1626): note: see reference to function template instantiation 'std::_Tree_node<std::pair<const Fortran::parser::CharBlock,Fortran::common::ConstantSubscript>,std::_Default_allocator_traits<_Alloc>::void_pointer> *std::_Tree<std::_Tmap_traits<_Kty,_Ty,_Pr,_Alloc,false>>::_Copy_nodes<std::_Tree<std::_Tmap_traits<_Kty,_Ty,_Pr,_Alloc,false>>::_Strategy::_Copy>(std::_Tree_node<std::pair<const Fortran::parser::CharBlock,Fortran::common::ConstantSubscript>,std::_Default_allocator_traits<_Alloc>::void_pointer> *,std::_Tree_node<std::pair<const Fortran::parser::CharBlock,Fortran::common::ConstantSubscript>,std::_Default_allocator_traits<_Alloc>::void_pointer> *)' being compiled
with
[
_Alloc=std::allocator<std::pair<const Fortran::parser::CharBlock,Fortran::common::ConstantSubscript>>,
_Kty=Fortran::parser::CharBlock,
_Ty=Fortran::common::ConstantSubscript,
_Pr=std::less<Fortran::parser::CharBlock>
]
...
C:\Program Files\Microsoft Visual Studio\2022\Preview\VC\Tools\MSVC\14.34.31823\include\map(109): note: while compiling class template member function 'std::map<Fortran::parser::CharBlock,Fortran::common::ConstantSubscript,std::less<Fortran::parser::CharBlock>,std::allocator<std::pair<const Fortran::parser::CharBlock,Fortran::common::ConstantSubscript>>>::map(const std::map<Fortran::parser::CharBlock,Fortran::common::ConstantSubscript,std::less<Fortran::parser::CharBlock>,std::allocator<std::pair<const Fortran::parser::CharBlock,Fortran::common::ConstantSubscript>>> &)'
D:\dev\repos\llvm-project\flang\include\flang/Evaluate/common.h(243): note: see reference to function template instantiation 'std::map<Fortran::parser::CharBlock,Fortran::common::ConstantSubscript,std::less<Fortran::parser::CharBlock>,std::allocator<std::pair<const Fortran::parser::CharBlock,Fortran::common::ConstantSubscript>>>::map(const std::map<Fortran::parser::CharBlock,Fortran::common::ConstantSubscript,std::less<Fortran::parser::CharBlock>,std::allocator<std::pair<const Fortran::parser::CharBlock,Fortran::common::ConstantSubscript>>> &)' being compiled
D:\dev\repos\llvm-project\flang\include\flang/Evaluate/common.h(291): note: see reference to class template instantiation 'std::map<Fortran::parser::CharBlock,Fortran::common::ConstantSubscript,std::less<Fortran::parser::CharBlock>,std::allocator<std::pair<const Fortran::parser::CharBlock,Fortran::common::ConstantSubscript>>>' being compiled
C:\Program Files\Microsoft Visual Studio\2022\Preview\VC\Tools\MSVC\14.34.31823\include\xtree(1664): warning C4530: C++ exception handler used, but unwind semantics are not enabled. Specify /EHsc
I try setting this flag just at the end of the if(MSVC) block in HandleLLVMOptions.cmake. Unfortunately, the build still fails and that’s when I notice that the earlier command lines in this post have the /EHs-c- flag. Looks like HandleLLVMOptions.cmake is explicitly removing such flags. The next logical step is to search for /EH in the codebase to see how it’s getting set for the commands that have it. That’s when I notice clang-cl – looks like a cl.exe immitation. Maybe this is how they’ve been building flang for windows without addressing all these Visual C++ issues?
Back to the exception handling issue: searching for /EHsc leads me to AddLLVM.cmake which references the LLVM_ENABLE_EH variable. Looks like that defaults to OFF in HandleLLVMOptions.cmake and it also needs LLVM_ENABLE_RTTI to be enabled.
The fact that this still doesn’t address the warning is the red flag forcing me to notice that this is a unit test and we probably don’t want to turn on RTTI anyway. That would be a huge change! Let’s drop these flags and instead modify the flang/unittests/CMakeLists.txt to add the -EHsc flag. That turns out to be exactly the right fix! Building with this command line takes about 1hr 55min on my desktop.
At this point, the commit I’ve been using and the Visual Studio build (17.4.0 Preview 3 with C++ compiler version 19.34.31823.3) are outdated. Let’s see what happens with the latest code and Visual Studio 17.4.0 Preview 4 (with C++ compiler version 19.34.31931). Bad timing on my part though, the installer now says Preview 5.0 is available and it comes with Microsoft (R) C/C++ Optimizing Compiler Version 19.34.31932 for x86. Not sure why these new preview builds are showing the x86 host when launching the developer command prompt from the start menu. Doesn’t happen when using the drop down in Windows Terminal.
One of the questions I had at the end of the Chemistry Basics II post was about how neurons were discovered. I guess these two channels have become my go to sources for these explanations. The Chadwick and the Neutron video presents a bit more history (e.g. the involvement of Marie Curie’s daughter).
chadwick and the neutron
I like the next video because it poses several questions that should be hints that the model without neutrons.
Atomic Structure: Discovery of the Neutron
The use of radiation in these experiments naturally raises the question of how these various types of radiation were discovered. Kathy Loves Physics addresses this in her video.
The Graph Isomorphism problem currently has a deterministic quasi-polynomial time algorithm. This time bound is a breakthrough from the previously best known upper bound of exponential time (in the size of the graph). I started looking at Babai’s paper on [1512.03547] Graph Isomorphism in Quasipolynomial Time (arxiv.org). Many of the key concepts involve abstract algebra, e.g. automorphism groups. This video is a great refresher on automorphisms.
The “Graph Isomorphism in Quasipolynomial Time” paper is quite involved. I was pleasantly surprised to find a University of Chicago lecture by Babai on this result few months ago. I still came away short of understanding the proof after watching the video.
We had an aviation and computers club in high school. The student that led the club was very knowledgeable about all sorts of aircraft and their capabilities. I have recently been learning more about the V-22 Osprey and thought I might as well save links to the more informative videos I’ve watched. It is this exercise that reminded me of that high school club. There are many videos on the V-22 out there. The video below provides a good introduction to the V-22, perhaps the most recognizable tilt rotor aircraft out there.
The V-22 Osprey: US Most Advanced Hybrid Aircraft Ever Built
One of the things I particularly liked about the video below was that it showed engineers working on aircraft models (e.g. propellers) in SolidWorks. Here’s a screenshot of a SolidWorks model at about 14:42 into the video above.
Another interesting video on the V-22 is this one from Business Insider. I like that it presents a bit more about the operational aspects of how the marines use the V-22.
Unfortunately, there have been many fatal accidents involving the V-22 Osprey. Ward Carroll discusses this troubled history and how the program made it through to today, at which point the V-22s have been grounded.
Chemistry Basics I covered the sections on scientific discovery up to atomic theory. Next is the question of what atoms are made of. Enter JJ Thomson with his CRT experiments. These 3 videos explain his discovery of the electron. I watched multiple just to see different perspectives on the same experiment.
It was after watching the next one that I found myself wondering how you pump all the air out of a glass bottle.
Discovery of the Electron: Cathode Ray Tube Experiment
JJ Thomson and the discovery of the electron
After it had been established that electrons exist and that they have negative charge, it naturally follows that we would want to know what the charge on an electron actually is. This was resolved by Millikan’s oil drop experiment.
This next video on the oil drop experiment was helpful because it showed a similar but modern setup.
The discovery of electrons, combined with the fact that matter is in general electrically neutron implies that there must be positively charged particles. Ernest Rutherford’s gold foil experiment confirms this:
At this point I have several questions that will have to wait for another time.
How are magnets made (e.g. the ones used by J.J. Thomson)?
How were alpha particles Rutherford was using discovered?
How was it shown that the electrons move around the nucleus?
It’s been over 20 years since I last studied chemistry. I started reading General Chemistry: Atoms First. It has an introductory chapter 0 that goes over concepts like fundamental units and conversion between units. A mention of the amount of volcanic material ejected into the atmosphere by the Krakatoa volcanic erruption piqued my curiosity enough to watch this History channel video.
Krakatoa: Devastating Explosion | How the Earth Was Made (S1, E3) | Full Episode | History
Digging into chapter one opened my eyes to the fascinating journey of many scientists through the centuries trying to understand the world, and more specifically, elements. Accounting for the similarities between many of the elements was an undertaking that got a breakthrough in Dmitri Mendeleev’s periodic table as explained in the next video.
The genius of Mendeleev’s periodic table – Lou Serico
Reading about the isolation of oxygen from mercury oxide by Joseph Priestley made me curious about how this was done. Thankfully, there are many informative videos on these topics. Here’s one on the isolation of oxygen.
The Discovery of Oxygen & Combustion 1946 Educational Film 76244
This video has left me wondering where HgO came from – was it a compound they used for something else?
Antoine Lavoisier soon afterwards demonstrated the law of mass conservation.
Joseph Proust followed with the law of definite proportions.
John Dalton capped off the line of inquiry with the law of multiple proportions.
Searching for Joseph Proust on YouTube leads me to this interesting video with some of this history.
The Creation of Chemistry – The Fundamental Laws: Crash Course Chemistry #3
I wish I had all these videos as a tool when I was learning chemistry years ago.
I have learned about various software packages this year. One of them is SolidWorks 2023. The tutorials I worked through started with how to model a flange. I figured I should probably know exactly what these are used for. Here’s a good video explaining what flanges are and the various types of flanges.
Piping Flange Types, Faces, and Surfaces – Explained!
One of the concepts introduced in this video is a gasket. I’ve heard the term used a lot but never really paid attention to exactly what a gasket is. This was a helpful breakdown of gaskets: Types of gaskets and gasket fundamental. – YouTube.
