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.
I’m reading through Venkatesan Guruswami’s thesis titled List Decoding of Error-Correcting Codes and the definition of infinite families of codes uses lim inf. These videos are a good reminder of how the superior and inferior limits are defined.
Real Analysis 11 | Limit Superior and Limit Inferior
Real Analysis 12 | Examples for Limit Superior and Limit Inferior
While we’re at it, why not review vector spaces since they are used in the definition of linear error correcting codes?
I have been learning a little bit about how things are made. One of the important concepts that is emphasized is GD&T. Here are the YouTube videos I found explaining what it is and why it is important.
Understanding GD&T
The next playlist was particularly interesting to me because of the discussion in one of the videos about how mechanical engineers often graduate without a basic knowledge of GD&T, which can set them back when they get into the industry.
I recently bought a 3D printer for some SolidWorks 2023 models I have been working on. I was reading through the applications of SolidWorks but was struggling to motivate myself to read through the overview of 3D printing technologies. I was therefore thrilled to find this series on Material Science in Additive Manufacturing: Basics. These are the technologies I reviewed (with the first two videos embedded at the end of this post):
Skipping the package repository setup step will result in these errors (seen on x64 5.10.102.1-microsoft-standard-WSL2 but all other steps and output are from a VM):
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Package docker-ce is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package 'docker-ce' has no installation candidate
E: Unable to locate package docker-ce-cli
E: Unable to locate package containerd.io
E: Couldn't find any package by glob 'containerd.io'
E: Couldn't find any package by regex 'containerd.io'
E: Unable to locate package docker-buildx-plugin
E: Unable to locate package docker-compose-plugin
I list the available containers by running docker ps and there are none, but this verifies that docker is working.
saint@ubuntuvm:~$ sudo docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
saint@ubuntuvm:~$
The hello-world image runs successfully as well.
saint@ubuntuvm:~$ sudo docker run hello-world
Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
719385e32844: Pull complete
Digest: sha256:88ec0acaa3ec199d3b7eaf73588f4518c25f9d34f58ce9a0df68429c5af48e8d
Status: Downloaded newer image for hello-world:latest
Hello from Docker!
This message shows that your installation appears to be working correctly.
To generate this message, Docker took the following steps:
1. The Docker client contacted the Docker daemon.
2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
(amd64)
3. The Docker daemon created a new container from that image which runs the
executable that produces the output you are currently reading.
4. The Docker daemon streamed that output to the Docker client, which sent it
to your terminal.
To try something more ambitious, you can run an Ubuntu container with:
$ docker run -it ubuntu bash
Share images, automate workflows, and more with a free Docker ID:
https://hub.docker.com/
For more examples and ideas, visit:
https://docs.docker.com/get-started/
saint@ubuntuvm:~$
Running Docker in WSL
I followed the above steps to install docker in my Windows Subsystem for Linux Ubuntu 22.04.2 LTS environment. Unfortunately, docker ps does not work.
saint@mymachine:~$ sudo docker ps
Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?
saint@mymachine:~$
To change the active code page, go to Control Panel > Region. Click on the “Change system locale…” button in the Administrative tab.
The Region Dialog Box
The Region Settings dialog will pop up. Select a different locale e.g. Japanese (Japan).
Reboot when prompted. You can verify (even before rebooting) that the active and OEM code pages have changed. Locales like Kiswahili (Kenya) and English (India) did not change the code page values (and therefore didn’t prompt to reboot).
After rebooting, I delete the build directory then configure and build OpenJDK again. This time the build fails with these errors:
ERROR: Build failed for target 'images' in configuration 'windows-x86_64-server-slowdebug' (exit code 2)
Stopping javac server
=== Output from failing command(s) repeated here ===
* For target hotspot_variant-server_libjvm_gtest_objs_test_json.obj:
test_json.cpp
d:\java\forks\jdk\test\hotspot\gtest\utilities\test_json.cpp(357): error C2143: syntax error: missing ')' before ']'
d:\java\forks\jdk\test\hotspot\gtest\utilities\test_json.cpp(355): error C2660: 'JSON_GTest::test': function does not take 1 arguments
d:\java\forks\jdk\test\hotspot\gtest\utilities\test_json.cpp(49): note: see declaration of 'JSON_GTest::test'
d:\java\forks\jdk\test\hotspot\gtest\utilities\test_json.cpp(355): note: while trying to match the argument list '(const char [171])'
d:\java\forks\jdk\test\hotspot\gtest\utilities\test_json.cpp(357): error C2143: syntax error: missing ';' before ']'
d:\java\forks\jdk\test\hotspot\gtest\utilities\test_json.cpp(357): error C2059: syntax error: ']'
d:\java\forks\jdk\test\hotspot\gtest\utilities\test_json.cpp(357): error C2017: illegal escape sequence
d:\java\forks\jdk\test\hotspot\gtest\utilities\test_json.cpp(357): error C2059: syntax error: ')'
d:\java\forks\jdk\test\hotspot\gtest\utilities\test_json.cpp(363): error C2143: syntax error: missing ')' before ']'
d:\java\forks\jdk\test\hotspot\gtest\utilities\test_json.cpp(361): error C2660: 'JSON_GTest::test': function does not take 1 arguments
d:\java\forks\jdk\test\hotspot\gtest\utilities\test_json.cpp(49): note: see declaration of 'JSON_GTest::test'
d:\java\forks\jdk\test\hotspot\gtest\utilities\test_json.cpp(361): note: while trying to match the argument list '(const char [174])'
d:\java\forks\jdk\test\hotspot\gtest\utilities\test_json.cpp(363): error C2143: syntax error: missing ';' before ']'
d:\java\forks\jdk\test\hotspot\gtest\utilities\test_json.cpp(363): error C2059: syntax error: ']'
... (rest of output omitted)
* All command lines available in /cygdrive/d/java/forks/jdk/build/windows-x86_64-server-slowdebug/make-support/failure-logs.
=== End of repeated output ===
No indication of failed target found.
HELP: Try searching the build log for '] Error'.
HELP: Run 'make doctor' to diagnose build problems.
The Visual C++ compiler’s behavior when reading source files depends on whether or not source files have a byte-order mark.
By default, Visual Studio detects a byte-order mark to determine if the source file is in an encoded Unicode format, for example, UTF-16 or UTF-8. If no byte-order mark is found, it assumes that the source file is encoded in the current user code page, unless you’ve specified a code page by using /utf-8 or the /source-charset option.
This can be easily tested using hexdump in Cygwin. Launch notepad and open the test.txt file created by these commands. The File > Save as dialog has an Encoding dropdown that write a byte-order marker for any of the UTF options. Running hexdump will display the byte-order markers.
echo abc123 > test.txt
hexdump -C test.txt
Inspect the OpenJDK source file failing to build confirms that there is no BOM in the file. (can this be done on GitHub?)
diff --git a/make/autoconf/flags-cflags.m4 b/make/autoconf/flags-cflags.m4
index c0c78ce95b6..bbb0426c368 100644
--- a/make/autoconf/flags-cflags.m4
+++ b/make/autoconf/flags-cflags.m4
@@ -560,7 +560,9 @@ AC_DEFUN([FLAGS_SETUP_CFLAGS_HELPER],
TOOLCHAIN_CFLAGS_JVM="-qtbtable=full -qtune=balanced -fno-exceptions \
-qalias=noansi -qstrict -qtls=default -qnortti -qnoeh -qignerrno -qstackprotect"
elif test "x$TOOLCHAIN_TYPE" = xmicrosoft; then
- TOOLCHAIN_CFLAGS_JVM="-nologo -MD -Zc:preprocessor -Zc:strictStrings -Zc:inline -MP"
+ # The -utf8 option sets source and execution character sets to UTF-8 to enable correct
+ # compilation of all source files regardless of the active code page on Windows.
+ TOOLCHAIN_CFLAGS_JVM="-nologo -MD -Zc:preprocessor -Zc:strictStrings -Zc:inline -MP -utf-8"
TOOLCHAIN_CFLAGS_JDK="-nologo -MD -Zc:preprocessor -Zc:strictStrings -Zc:inline -Zc:wchar_t-"
fi
The build still fails but this time the error is from the java.desktop tree.
ERROR: Build failed for target 'images' in configuration 'windows-x86_64-server-slowdebug' (exit code 2)
=== Output from failing command(s) repeated here ===
* For target support_native_java.desktop_libfreetype_afblue.obj:
afblue.c
d:\java\forks\jdk\src\java.desktop\share\native\libfreetype\src\autofit\afblue.c(1): error C2220: the following warning is treated as an error
d:\java\forks\jdk\src\java.desktop\share\native\libfreetype\src\autofit\afblue.c(1): warning C4819: The file contains a character that cannot be represented in the current code page (932). Save the file in Unicode format to prevent data loss
d:\java\forks\jdk\src\java.desktop\share\native\libfreetype\src\autofit\afscript.h(1): warning C4819: The file contains a character that cannot be represented in the current code page (932). Save the file in Unicode format to prevent data loss
d:\java\forks\jdk\src\java.desktop\share\native\libfreetype\src\autofit\afblue.c(257): warning C4819: The file contains a character that cannot be represented in the current code page (932). Save the file in Unicode format to prevent data loss
... (rest of output omitted)
* For target support_native_java.desktop_libfreetype_afcjk.obj:
afcjk.c
...
Let us try using JITWatch on the sample Factorization program I have been using to learn about systems performance. Use these instructions from that blog post to get JITWatch:
git clone https://github.com/AdoptOpenJDK/jitwatch.git
cd jitwatch
mvn clean package
# Produces an executable jar in ui/target/jitwatch-ui-shaded.jar
java -jar ui/target/jitwatch-ui-shaded.jar
Start the factorization sample application such that a hotspot log file is generated. To do so, use the flags listed in the JITWatch Instructions · AdoptOpenJDK/jitwatch Wiki (github.com). I decide to redirect the output to a file to avoid filling the script with the additional logging output.
Click on the “Open Log” button in JITWatch then select the hotspot*.log file. Next, click on the Start button to process the JIT log.
Opening a HotSpot Log FileProcessed HotSpot LogViewing JIT-compiled Class Members
Clicking on a class member opens another window with the corresponding assembly instructions generated by the JIT. I haven’t set up any source code locations but the assembly instructions are still displayed.
Setting up MVN on Windows
To run JITWatch on Windows, download the Maven binaries from Maven – Download Apache Maven and verify the hashes using certutil. Extract the downloaded .zip file using tar. Here are the instructions I used in Git Bash.
mkdir -p /c/java/binaries/apache
cd /c/java/binaries/apache
curl -Lo apache-maven-3.9.3-bin.zip https://dlcdn.apache.org/maven/maven-3/3.9.3/binaries/apache-maven-3.9.3-bin.zip
certutil -hashfile apache-maven-3.9.3-bin.zip SHA512
# shasum -a 512 apache-maven-3.9.3-bin.zip
tar xf apache-maven-3.9.3-bin.zip
Paste the lines below into a Dockerfile. See the Dockerfile reference for more information about Dockerfile commands.
FROM mcr.microsoft.com/cbl-mariner/base/core:2.0
Build the image by running docker build -t testimage . in the directory containing the Dockerfile. The output looks like this (hashes truncated to 16 characters):
It is sometimes essential to have the container run in detached mode, e.g. when you have a single command line interface available (e.g. via SSH) and don’t want to connect to the host again. Start the container using docker run then connect to it using docker attach.
docker run -dit --name mycontainer testimage
docker attach mycontainer
Other than the machine name, WSL’s Ubuntu 22.04.2 LTS has the same uname -a output as the docker container from the test image created above (on my x64 Windows 11 machine): Linux 9a13d5e98075 5.10.102.1-microsoft-standard-WSL2 #1 SMP Wed Mar 2 00:30:59 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux.
As I learn about systems performance, one question that often arises is who is responsible for the context switching on a system. In Linux, the number of context switches per second is displayed by vmstat. To see this information every second, for example, run vmstat 1. Here is sample output from my Ubuntu 22.04 VM showing about 50000 context switches per sec. I used the -SM option to display memory info in Megabytes (which reduces the amount of output per line). The last (optional) argument is the number of updates (lines) to be displayed.
saint@ubuntuvm:~$ vmstat -SM 1 5
procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
r b swpd free buff cache si so bi bo in cs us sy id wa st
2 0 0 4603 386 5176 0 0 1 5 16 7 35 6 59 0 0
4 0 0 4603 386 5176 0 0 0 88 20031 45649 51 8 41 0 0
4 0 0 4603 386 5176 0 0 0 0 23768 52532 49 8 43 0 0
4 0 0 4603 386 5176 0 0 0 0 23826 52931 49 7 43 0 0
5 0 0 4603 386 5176 0 0 0 0 23328 51731 49 9 43 0 0
Use pidstat to get a per-process breakdown of context switches per second. Like vmstat, a report delay and a report count can be specified. Without specifying any specific flags, the default output is a breakdown of CPU usage.
For our purposes, we need to specify the -w flag to report task switching activity. After the specified number of reports have been displayed, the average number of context switches (voluntary and involuntary) are displayed.
I happened to have my factorization Java application running on this VM. Interestingly, it does not appear in this output despite the fact that the time command displays a large number of context switches for this application. To see this, set up the application as described in the next section.
Running a Sample Multithreaded Application
Clone the scratchpad repo then compile and launch the factorization application using these instructions (with any necessary changes to the JAVA_HOME path):
# Download a Java build if necessary
mkdir -p ~/java/binaries/jdk/x64
cd ~/java/binaries/jdk/x64
wget https://aka.ms/download-jdk/microsoft-jdk-17.0.7-linux-x64.tar.gz
tar xzf microsoft-jdk-17.0.7-linux-x64.tar.gz
# Set the JAVA_HOME environment variable
export JAVA_HOME=~/java/binaries/jdk/x64/jdk-17.0.7+7
# Get the Factorization source code
mkdir ~/repos
cd ~/repos
git clone https://github.com/swesonga/scratchpad
cd scratchpad/demos/java/FindPrimes
# Compile the factorization source code
$JAVA_HOME/bin/javac Factorize.java
# Factorize a number and display task statistics
/usr/bin/time -v $JAVA_HOME/bin/java Factorize 897151542039582592342572091 CUSTOM_THREAD_COUNT_VIA_THREAD_CLASS 6
Notice the context switching statistics when the command completes:
Command being timed: "/home/saint/java/binaries/jdk/x64/jdk-20+36/bin/java Factorize 897151542039582592342572091 CUSTOM_THREAD_COUNT_VIA_THREAD_CLASS 6"
User time (seconds): 37.59
System time (seconds): 6.47
Percent of CPU this job got: 363%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:12.12
Average shared text size (kbytes): 0
Average unshared data size (kbytes): 0
Average stack size (kbytes): 0
Average total size (kbytes): 0
Maximum resident set size (kbytes): 298576
Average resident set size (kbytes): 0
Major (requiring I/O) page faults: 8
Minor (reclaiming a frame) page faults: 70247
Voluntary context switches: 367393
Involuntary context switches: 1337
Swaps: 0
File system inputs: 0
File system outputs: 64
Socket messages sent: 0
Socket messages received: 0
Signals delivered: 0
Page size (bytes): 4096
Exit status: 0
Per-Thread Task Switching Information
How can get some insight into the context switching in the Java process? We can also display statistics for threads associated with selected tasks using the -t option. We now get insight into Java’s contribution to context switching:
Given the large number of tasks on the system, it may be helpful to focus on Java alone. Running jps shows the pids of the Java processes running. We can pass the PID of interest to pidstat. Only context switches for that process will now be displayed, e.g.
To store encrypted git credentials on disk in Ubuntu, install pass and the git-credential-manager. We will use gpg to generate a key that pass will use for secure storage and retrieval of credentials. Use these commands to get everything set up for git:
saint@ubuntuvm:~/repos/scratchpad$ git push
Username for 'https://github.com': swesonga
Password for 'https://swesonga@github.com':
remote: Permission to swesonga/scratchpad.git denied to swesonga.
fatal: unable to access 'https://github.com/swesonga/scratchpad/': The requested URL returned error: 403
saint@ubuntuvm:~/repos/scratchpad$ sudo dpkg -i ~/Downloads/gcm-linux_amd64.2.1.2.deb
[sudo] password for saint:
Selecting previously unselected package gcm.
(Reading database ... 272980 files and directories currently installed.)
Preparing to unpack .../gcm-linux_amd64.2.1.2.deb ...
Unpacking gcm (2.1.2) ...
Setting up gcm (2.1.2) ...
saint@ubuntuvm:~/repos/scratchpad$ which git-credential-manager
/usr/local/bin/git-credential-manager
saint@ubuntuvm:~/repos/scratchpad$ git-credential-manager configure
Configuring component 'Git Credential Manager'...
Configuring component 'Azure Repos provider'...
The git push experience is now different:
saint@ubuntuvm:~/repos/scratchpad$ git push
fatal: No credential store has been selected.
Set the GCM_CREDENTIAL_STORE environment variable or the credential.credentialStore Git configuration setting to one of the following options:
secretservice : freedesktop.org Secret Service (requires graphical interface)
gpg : GNU `pass` compatible credential storage (requires GPG and `pass`)
cache : Git's in-memory credential cache
plaintext : store credentials in plain-text files (UNSECURE)
See https://aka.ms/gcm/credstores for more information.
Username for 'https://github.com':
saint@ubuntuvm:~/repos/scratchpad$ git config --global credential.credentialStore
saint@ubuntuvm:~/repos/scratchpad$ git push
fatal: Password store has not been initialized at '/home/saint/.password-store'; run `pass init <gpg-id>` to initialize the store.
See https://aka.ms/gcm/credstores for more information.
Username for 'https://github.com':
Since I own the VM, I don’t mind credentials being stored on disk (but not in plain text), so I set up gpg and pass as instructed.
saint@ubuntuvm:~$ gpg --gen-key
gpg (GnuPG) 2.2.27; Copyright (C) 2021 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Note: Use "gpg --full-generate-key" for a full featured key generation dialog.
GnuPG needs to construct a user ID to identify your key.
Real name: Saint Wesonga
Email address: saint@swesonga.org
You selected this USER-ID:
"Saint Wesonga <saint@swesonga.org>"
...
saint@ubuntuvm:~$ sudo apt install pass
[sudo] password for saint:
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following additional packages will be installed:
libqrencode4 qrencode tree xclip
Suggested packages:
libxml-simple-perl python ruby
The following NEW packages will be installed:
libqrencode4 pass qrencode tree xclip
0 upgraded, 5 newly installed, 0 to remove and 92 not upgraded.
Need to get 151 kB of archives.
After this operation, 442 kB of additional disk space will be used.
Do you want to continue? [Y/n]
...
saint@ubuntuvm:~$ pass init ABCDEF0123456789
mkdir: created directory '/home/saint/.password-store/'
Password store initialized for ABCDEF0123456789
Apparently I used the wrong value for the key but git push is unfazed – it pushes successfully after the browser authentication completes. I’m not sure what is happening now since browser authentication is in use but as long as I can push, I can forge ahead with other tasks.
saint@ubuntuvm:~/repos/scratchpad$ git push
info: please complete authentication in your browser...
fatal: Failed to encrypt file '/home/saint/.password-store/git/https/github.com/swesonga.gpg' with gpg. exit=2, out=, err=gpg: <WRONG HEX VALUE>: skipped: No public key
gpg: [stdin]: encryption failed: No public key
Enumerating objects: 11, done.
Counting objects: 100% (11/11), done.
Delta compression using up to 6 threads
Compressing objects: 100% (5/5), done.
Writing objects: 100% (6/6), 745 bytes | 745.00 KiB/s, done.
Total 6 (delta 3), reused 0 (delta 0), pack-reused 0
remote: Resolving deltas: 100% (3/3), completed with 3 local objects
Update: 2023-09-20. Use pass rm -r git to authenticate in the browser the next time git push is executed (e.g. if the password store secret is lost).
