dev container for OpenMP backend by science-enthusiast · Pull Request #8 · CExA-project/CExA-Experimental

science-enthusiast · 2026-04-13T11:59:48Z

Dev container for IDEs like VSCode for Kokkos OpenMP backend.

More details in the README.md file.

tretre91

I could get the dev container to work with both docker and podman on a desktop with

Fedora 43
docker 29.4.3
podman 5.8.2
vscode 1.119.0

tretre91 · 2026-05-07T17:24:27Z

+          } 
+      }
+  },
+  "postStartCommand": "cmake -DKokkos_ROOT=/opt/kokkos-install -DKokkos_ENABLE_OPENMP=ON -B build"


No need to repeat Kokkos_ENABLE_OPENMP here.
Using CMAKE_EXPORT_COMPILE_COMMANDS=ON will tell CMake to produce a compile_commands.json file, which can then be used by the C++ extension (or any other language server protocol extension) to get the info about the include path and the flags

Suggested change

"postStartCommand": "cmake -DKokkos_ROOT=/opt/kokkos-install -DKokkos_ENABLE_OPENMP=ON -B build"

"postStartCommand": "cmake -DKokkos_ROOT=/opt/kokkos-install -DCMAKE_EXPORT_COMPILE_COMMANDS=ON -B build"

I am not sure why -DKokkos_ENABLE_OPENMP=ON was added here. It should go.

tretre91 · 2026-05-07T17:28:33Z

+          "settings": { 
+            "C_Cpp.default.includePath": [
+              "/opt/kokkos-install/include/"
+            ]


This is the setting used by the C++ extension to locate the compile_commands.json, cmake puts it in the build directory.
Using this, Kokkos symbols are correctly recognized by Intellisense, it also removes the need for the export CPATH=...

Suggested change

]

],

"C_Cpp.default.compileCommands": [

"./build/compile_commands.json"

]

Thank you. Nice to know.

tretre91 · 2026-05-07T17:28:53Z

@@ -0,0 +1,22 @@
+FROM mcr.microsoft.com/vscode/devcontainers/cpp:ubuntu-22.04
+
+# Install C++ development tools, Git and CMake 


Trailing space

Suggested change

# Install C++ development tools, Git and CMake

# Install C++ development tools, Git and CMake

tretre91 · 2026-05-07T17:29:20Z

+               "ms-vscode.cpptools-extension-pack",
+               "ms-azuretools.vscode-docker"
+          ],
+          "settings": { 


Trailing space

Suggested change

"settings": {

"settings": {

Thank you for your time, Trévis.

I am curious to know what approach you take to identify trailing white spaces in a file.

My editor is configured to show spaces at the end of a line as visible characters (see the list and listchars options in vim)

I will look into those vim options.

tretre91 · 2026-05-07T17:31:03Z

+    cmake
+
+RUN git clone https://github.com/kokkos/kokkos.git \
+    --branch release-candidate-4.6.01 --depth=1 /opt/kokkos && \


We can use a more recent kokkos version (and the release-candidate-4.6.01 branch doesn't exist anymore)

Suggested change

--branch release-candidate-4.6.01 --depth=1 /opt/kokkos && \

--branch 5.1.1 --depth=1 /opt/kokkos && \

tretre91 · 2026-05-07T17:45:19Z

+
+There is a simple C++ project that links with [Kokkos](https://cexa-project.org/news/2025-03-19-ninth-kokkos-tea-time/) to be built and run in `devc_hellow`. One can see in the `CMakeLists.txt` file that CMake expects Kokkos to be installed, in order to build the project. The container image takes care of this requirement.
+
+In `devcontainer.json`, one can specify a "postStartCommand". For e.g., it is defined as "cmake -DKokkos_ROOT=/opt/kokkos-install -DKokkos_ENABLE_OPENMP=ON -B build" in our case. This ensures that a `build` directory is generated by CMake. See below for some observations with Docker and Podman regarding "postStartCommand". 


Suggested change

In `devcontainer.json`, one can specify a "postStartCommand". For e.g., it is defined as "cmake -DKokkos_ROOT=/opt/kokkos-install -DKokkos_ENABLE_OPENMP=ON -B build" in our case. This ensures that a `build` directory is generated by CMake. See below for some observations with Docker and Podman regarding "postStartCommand".

In `devcontainer.json`, one can specify a "postStartCommand". For e.g., it is defined as "cmake -DKokkos_ROOT=/opt/kokkos-install -DCMAKE_EXPORT_COMPILE_COMMANDS=ON -B build" in our case. This ensures that a `build` directory is generated by CMake, and that compile commands are exported (helpful for getting Intellisense to work). See below for some observations with Docker and Podman regarding "postStartCommand".

tretre91 · 2026-05-07T17:46:57Z

+* Currently, "postStartCommand" works only with Docker and not with Podman. One gets an error like the following with Podman:
+
+      Error: error parsing environment variables: name "\afbfa9712-93dc-4bca-8ecc-99ffb315ae27\x1b]0;vscode@mdlspc111.extra.cea.fr: cat /proc/self/environ\aREMOTE_CONTAINERS_IPC" has white spaces, poorly formatted name
+      [147463 ms] postStartCommand from devcontainer.json failed with exit code 125. Skipping any further user-provided commands.
+* Podman takes more time to build and run the container. Probably, it takes more time to restart a container also.
+* With Podman, VS Code disconnects and reconnects to the container from time to time.
+
+Probably, these issues with Podman can be resolved by using a more recent version of Podman. For example, VS Code recommends version 5+. However, Podman offers much better support for Red Hat distributions like Fedora. 


Note that I did not get any issue using podman, but as you mention it might be because I have a fairly recent version (5.8.2)

tretre91 · 2026-05-07T17:47:18Z

+
+#### Some technical points
+* In order to enable networking while building the container, define `"build"` as `"build": { …, "options": ["--network=host"], …}`. This may be needed in order to `git clone` the Kokkos repository.  Also, note that `“runArgs”: [“--network=host”]` is for enabling network connection while running the container.
+* Setting the environment variable `CPATH` as `CPATH="/opt/kokkos-install/include:$CPATH"` helps with IntelliSense recognizing Kokkos header files.


Suggested change

* Setting the environment variable `CPATH` as `CPATH="/opt/kokkos-install/include:$CPATH"` helps with IntelliSense recognizing Kokkos header files.

tretre91 · 2026-05-07T17:48:07Z

+* In the Command Palette enter ">Dev Containers: Rebuild Without Cache and Reopen in Container" whenever you need to rebuild the container after making changes to either `devcontainer.json` or `Dockerfile`.
+
+#### To explore further
+* Kokkos functions are incorrectly flagged by IntelliSense.


Addressed by the compile_commands thing

Suggested change

* Kokkos functions are incorrectly flagged by IntelliSense.

tretre91 · 2026-05-07T17:51:47Z

+* Try installing the following extensions in VS Code to check for a better experience with Podman.
+  * "Container Tools" and "Pod Manager". Note: These extensions have been released relatively recently.


I only needed to install the dev container extension for it to work

dev container for OpenMP backend

bdf40ec

science-enthusiast force-pushed the kokkos-dev-container branch from f64b124 to bdf40ec Compare April 13, 2026 12:41

tretre91 self-requested a review April 15, 2026 10:06

tretre91 reviewed May 7, 2026

View reviewed changes

	"postStartCommand": "cmake -DKokkos_ROOT=/opt/kokkos-install -DKokkos_ENABLE_OPENMP=ON -B build"
	"postStartCommand": "cmake -DKokkos_ROOT=/opt/kokkos-install -DCMAKE_EXPORT_COMPILE_COMMANDS=ON -B build"

-            ]
+            ],
+            "C_Cpp.default.compileCommands": [
+              "./build/compile_commands.json"
+            ]

		@@ -0,0 +1,22 @@
		FROM mcr.microsoft.com/vscode/devcontainers/cpp:ubuntu-22.04

		# Install C++ development tools, Git and CMake

	--branch release-candidate-4.6.01 --depth=1 /opt/kokkos && \
	--branch 5.1.1 --depth=1 /opt/kokkos && \


		There is a simple C++ project that links with [Kokkos](https://cexa-project.org/news/2025-03-19-ninth-kokkos-tea-time/) to be built and run in `devc_hellow`. One can see in the `CMakeLists.txt` file that CMake expects Kokkos to be installed, in order to build the project. The container image takes care of this requirement.

		In `devcontainer.json`, one can specify a "postStartCommand". For e.g., it is defined as "cmake -DKokkos_ROOT=/opt/kokkos-install -DKokkos_ENABLE_OPENMP=ON -B build" in our case. This ensures that a `build` directory is generated by CMake. See below for some observations with Docker and Podman regarding "postStartCommand".

		* Try installing the following extensions in VS Code to check for a better experience with Podman.
		* "Container Tools" and "Pod Manager". Note: These extensions have been released relatively recently.

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science-enthusiast commented Apr 13, 2026

Uh oh!

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