Global CMake for tutorials #91

cedricchevalier19 · 2024-05-13T10:12:16Z

The goal is to provide a joint built for all exercises (and their solutions).

This way, compilation is straightforward for IDE users.

Currently, most of the exercises are built using the top-level CMake.
However, not all builds make sense, as CUDA builds are wrong for the first exercises. I have put configuration warnings when Kokkos is not configured correctly, as explaining why it is not working is still valuable.
I have also refactored the fetch_content implementation: ~~it is now called in an overloaded find_package to keep CMakeLists.txt as standard as possible~~.

The user can set three CMake variables to control the build system:

CMAKE_DISABLE_FIND_PACKAGE_Kokkos: to force a build of a custom Kokkos and ignore any installed Kokkos
CMAKE_REQUIRE_FIND_PACKAGE_Kokkos: to force finding an installed Kokkos and to fail if not found
KokkosTutorials_KOKKOS_SOURCE_PATH: to specify a Kokkos source directory and by-pass fetch_content when building a custom Kokkos.

~~I can improve the global CMake by using external_project for the first exercises to "sandbox" their builds and allow a custom Kokkos.~~

cedricchevalier19 · 2024-06-05T09:33:05Z

One difficulty is that the first 3-4 exercises are not perfect Kokkos code and can have issue when a Kokkos device backend is enabled.

This way, the CMakeLists.txt is almost standard. Remove old common.cmake

…xercises

advanced_reductions.cpp and parallel_scan.cpp cannot compile due to missing code (the exercise).

Use "" for include instead of <> to avoid adding `-I.` flag.

Still have to check on a Cuda computer.

This allows to not pollute the source directory.

This way we can promote the use of SHA256

cedricchevalier19 · 2025-02-26T13:25:10Z

@JBludau and @dalg24, I finally decided to follow your advice and I've factorized the code checking for a gpu. Furthermore, to apply the good practice described in the documentation to use either find_package and fetch_content, I have reverted to hide the magic behind a custom FindKokkos.cmake.

I can update the CI to use the new global CMake but I think it is better to leave it to a separate PR, this one being already too large.

I do not understand the issue with Windows but it looks similar to the one of #107.

Exercises/cmake/SetUpKokkos.cmake

pzehner · 2025-02-26T13:42:13Z

Exercises/cmake/SetUpKokkos.cmake

+else ()
+    if (EXISTS ${KokkosTutorials_KOKKOS_SOURCE_DIR})
+        add_subdirectory(${KokkosTutorials_KOKKOS_SOURCE_DIR} Kokkos)
+    else ()


Leave early here too?

Not blocking but do you know how does that play with multi-config generators?

I will test and report it.

It worked for my experiments.

README.md

pzehner · 2025-02-26T14:02:38Z

So, creating a custom FindKokkos.cmake is not a good idea?

CMakeLists.txt

dalg24 · 2025-02-26T14:20:54Z

Exercises/cmake/SetUpKokkos.cmake

+else ()
+    if (EXISTS ${KokkosTutorials_KOKKOS_SOURCE_DIR})
+        add_subdirectory(${KokkosTutorials_KOKKOS_SOURCE_DIR} Kokkos)
+    else ()


Not blocking but do you know how does that play with multi-config generators?

Exercises/cmake/SetUpKokkos.cmake

CMakeLists.txt

Co-authored-by: Paul Zehner <[email protected]>

…r19/cmake # Conflicts: # Exercises/tasking/Begin/CMakeLists.txt # Exercises/tasking/Solution/CMakeLists.txt

pzehner

I still have some concerns with the setup script.

Exercises/SetUpKokkos.cmake

pzehner · 2025-05-19T13:07:05Z

Exercises/SetUpKokkos.cmake

+# the default directory is inside the source tree.
+# This might break if the default in source directory is called from multiple cmake instances at the same time.
+
+set(KokkosTutorials_KOKKOS_SOURCE_DIR "dep/kokkos" CACHE PATH "Description for KokkosTutorials_KOKKOS_SOURCE_DIR")


Please update the help message.

Also, this downloads Kokkos in the build directory. One point of Damien was to use a common directory to not re-download it for every exercice, and I pretty much agree with him. In my experience though, since we have several projects cascading, it is tedious to do it right (maybe with CMAKE_CURRENT_LIST_DIR).

Should be OK now.

…r19/cmake

Does not require CMake 3.14 anymore.

pzehner

Good job for updating the PR, I think we're almost there!

pzehner · 2025-07-28T09:20:20Z

Exercises/SetUpKokkos.cmake

+    set(CMAKE_BUILD_TYPE "${default_build_type}" CACHE STRING
+            "Choose the type of build, options are: Debug, Release, RelWithDebInfo and MinSizeRel."
+            FORCE)
+endif ()


Then, if Kokkos is already found, the build type is not specified for the files of the tutorial. Is it what we want?

I've kept how it was working. I do not really see any added value and I am happy to remove this part.

It's true that CMake always let the user choose what kind of build they want.

pzehner · 2025-07-28T09:25:40Z

Exercises/SetUpKokkos.cmake

+# Where to find Kokkos' source code. This might be set by the user.
+# In order to automatically share the download between exercises when they are compiled individually,
+# the default directory is inside the source tree.
+# This might break if the default in source directory is called from multiple cmake instances at the same time.


Can you elaborate?

If several CMake instances download at the same time I am not it will always work.

I see, maybe you can rework the sentence then.

Exercises/SetUpKokkos.cmake

pzehner · 2025-07-28T09:32:31Z

Exercises/multi_gpu_cuda/Begin/CMakeLists.txt

+    message(WARNING "This example requires CUDA, enable with -DKokkos_ENABLE_CUDA=ON")
+    return()


Suggested change

message(WARNING "This example requires CUDA, enable with -DKokkos_ENABLE_CUDA=ON")

return()

message(FATAL_ERROR "This example requires CUDA, enable with -DKokkos_ENABLE_CUDA=ON")

The code will not compile without Cuda.

Oh wait, if you do a global build, this would cancel it completely.

I am open to make it a fatal error but it means that we should protect the add_subdirectory.And potentially lose track of what is compiled or not.

You can always do the check in the parent CMakeLists.txt and do not add_subdirectory. It sounds like code duplication, although not dramatic for me.

pzehner · 2025-07-28T09:33:07Z

Exercises/multi_gpu_cuda/Solution/CMakeLists.txt

+  message(WARNING "This example requires CUDA, enable with -DKokkos_ENABLE_CUDA=ON")
+  return()


Suggested change

message(WARNING "This example requires CUDA, enable with -DKokkos_ENABLE_CUDA=ON")

return()

message(FATAL_ERROR "This example requires CUDA, enable with -DKokkos_ENABLE_CUDA=ON")

Oh wait, if you do a global build, this would cancel it completely.

README.md

pzehner · 2025-07-28T09:56:08Z

There is also a missing include:

diff --git a/Exercises/unique_token/Begin/unique_token.cpp b/Exercises/unique_token/Begin/unique_token.cpp
index 0af6bec..800a4f4 100644
--- a/Exercises/unique_token/Begin/unique_token.cpp
+++ b/Exercises/unique_token/Begin/unique_token.cpp
@@ -1,4 +1,5 @@
 #include<Kokkos_Core.hpp>
+#include <iostream>
 
 // EXERCISE: need to remove the ifdef...
 #ifdef KOKKOS_ENABLE_OPENMP

Co-authored-by: Paul Zehner <[email protected]>

JBludau

the rest seems reasonable

JBludau · 2025-07-28T13:48:52Z

.gitignore

+Exercises/dep
+*.o
+*.host
+*.cuda
+KokkosCore_config.h
+KokkosCore_config.tmp
+*.a
+


I am in general against .gitignores if possible ... I want to see what changed and I think devs should be aware of what they push ...

I think most of it can go out, besides Exercises/dep, since we're only relying on CMake. But I would add build*/.

I removed the .gitignore after a build to see what git status gives, and it's Kokkos sources and the build directories.

cedricchevalier19 added 5 commits March 9, 2020 15:33

Ignore object files in git.

9d26afe

Add a root CMakeLists.txt

1b2b56a

More exercises in the global CMake

50bf4e0

CMake directory order follows tutorial

56003c8

Adding SIMD to CMakeLists.txt

6268211

cedricchevalier19 mentioned this pull request Jun 5, 2024

Update build system #90

Open

4 tasks

cedricchevalier19 added 2 commits June 5, 2024 11:38

Use find_package(Kokkos REQUIRED) in all exercises

dec987e

This way, the CMakeLists.txt is almost standard. Remove old common.cmake

subview now compiles with the DefaultExecutionSpace.

4f30736

cedricchevalier19 force-pushed the cmake branch from be668f9 to 4f30736 Compare June 5, 2024 09:39

Add CMake warnings when using device enabled Kokkos for the 2 first e…

f2cc0c8

…xercises

cedricchevalier19 mentioned this pull request Jun 5, 2024

Update tutorial to get the latest release of Kokkos #92

Merged

cedricchevalier19 added 13 commits June 5, 2024 14:50

Adding 'instances' exercise to main CMake

9ebf652

Adding 'scatter_view/Usage' to CMake

c4451a0

Adding 'random_number' to CMake

1a9d282

Comment out some Kokkos call in Begin exercises

1b1dedc

advanced_reductions.cpp and parallel_scan.cpp cannot compile due to missing code (the exercise).

Adding 'unique_token' to CMake

1a07316

Adding 'unordered_map' to CMake

9bce058

Adding 'virtual_functions' to CMake

7c6a676

Use "" for include instead of <> to avoid adding `-I.` flag.

List exercises to add to global cmake.

8b5cd95

Add fortran_interface to global cmake

5779c0f

Add multi_gpu_cuda to global cmake

dacde70

Still have to check on a Cuda computer.

Add minimd to global cmake

2bc96df

Cleaning up exercise makefile.

46fa1d0

Fetch Kokkos sources into CMAKE_BINARY_DIR

d6e6530

This allows to not pollute the source directory.

cedricchevalier19 self-assigned this Jun 5, 2024

cedricchevalier19 marked this pull request as ready for review June 10, 2024 14:18

cedricchevalier19 requested review from dalg24, lucbv and masterleinad June 10, 2024 14:18

cedricchevalier19 added 2 commits February 26, 2025 12:51

Use tarball to download Kokkos

1c404fc

This way we can promote the use of SHA256

Fix include in mpi_exch directory

0b9221a

pzehner suggested changes Feb 26, 2025

View reviewed changes

dalg24 reviewed Feb 26, 2025

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AdRi1t reviewed Feb 26, 2025

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CMakeLists.txt Show resolved Hide resolved

cedricchevalier19 and others added 9 commits February 26, 2025 16:50

Update README.md

cd94126

Co-authored-by: Paul Zehner <[email protected]>

Update README.md

4ec18a0

Co-authored-by: Paul Zehner <[email protected]>

Update README.md

e0ee40b

Co-authored-by: Paul Zehner <[email protected]>

Fix unique_token example compilation

d21fe57

Cleaning up

d3daa7f

Move SetUpKokkos to Exercices

bffe62b

Merge remote-tracking branch 'upstream/main' into fork/cedricchevalie…

5f3a382

…r19/cmake # Conflicts: # Exercises/tasking/Begin/CMakeLists.txt # Exercises/tasking/Solution/CMakeLists.txt

Fix cmake policy for downloading Kokkos Core

cdb445f

Merge remote-tracking branch 'origin/master' into cmake

e514fc7

cedricchevalier19 requested a review from pzehner April 3, 2025 15:31

pzehner suggested changes May 19, 2025

View reviewed changes

cedricchevalier19 added 7 commits July 25, 2025 15:02

Download Kokkos in Exercises/dep

b148a85

Merge remote-tracking branch 'upstream/main' into fork/cedricchevalie…

8a3aca6

…r19/cmake

Remove references to tasking example

c47a017

Follow @pzehner advice to fix time stamping

21baf0d

Does not require CMake 3.14 anymore.

Add diagnostic messages for Kokkos location

1bafe0e

Upgrade to Kokkos 4.6.02

9e10417

Add an example with a custom Kokkos source directory

e6e1c66

pzehner suggested changes Jul 28, 2025

View reviewed changes

cedricchevalier19 and others added 2 commits July 28, 2025 15:09

Remove a confusing warning

0e4b265

Co-authored-by: Paul Zehner <[email protected]>

Simplify README.md

84c657b

Co-authored-by: Paul Zehner <[email protected]>

JBludau approved these changes Jul 28, 2025

View reviewed changes

		message(WARNING "This example requires CUDA, enable with -DKokkos_ENABLE_CUDA=ON")
		return()

	message(WARNING "This example requires CUDA, enable with -DKokkos_ENABLE_CUDA=ON")
	return()
	message(FATAL_ERROR "This example requires CUDA, enable with -DKokkos_ENABLE_CUDA=ON")

Global CMake for tutorials #91

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Global CMake for tutorials #91

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