solver: penalize language virtuals for each use#51314
Merged
tgamblin merged 1 commit intospack:developfrom Oct 27, 2025
Merged
Conversation
Member
Author
|
I tried to benchmark this one using this configuration: packages.yamlpackages:
gcc:
externals:
- spec: [email protected] languages:='c,c++,fortran'
prefix: /home/culpo/opt/compiler-as-deps/build-tools/.spack-env/view
extra_attributes:
compilers:
c: /home/culpo/opt/compiler-as-deps/build-tools/.spack-env/view/bin/gcc
cxx: /home/culpo/opt/compiler-as-deps/build-tools/.spack-env/view/bin/g++
fortran: /home/culpo/opt/compiler-as-deps/build-tools/.spack-env/view/bin/gfortran
- spec: [email protected] languages:='c,c++,fortran'
prefix: /usr
extra_attributes:
compilers:
c: /usr/bin/gcc-8
cxx: /usr/bin/g++-8
fortran: /usr/bin/gfortran-8
- spec: [email protected] languages:='c,c++,fortran'
prefix: /usr
extra_attributes:
compilers:
c: /usr/bin/gcc
cxx: /usr/bin/g++
fortran: /usr/bin/gfortran
- spec: [email protected] languages:='c,c++,fortran'
prefix: /usr
extra_attributes:
compilers:
c: /usr/bin/gcc-10
cxx: /usr/bin/g++-10
fortran: /usr/bin/gfortran-10
llvm:
externals:
- spec: [email protected]+clang~flang+lld~lldb
prefix: /usr
extra_attributes:
compilers:
c: /usr/bin/clang-12
cxx: /usr/bin/clang++-12
- spec: [email protected]+clang~flang~lld+lldb
prefix: /usr
extra_attributes:
compilers:
c: /usr/bin/clang
cxx: /usr/bin/clang++
- spec: [email protected]+clang~flang~lld~lldb
prefix: /usr
extra_attributes:
compilers:
c: /usr/bin/clang-11
cxx: /usr/bin/clang++-11
c:
prefer:
- llvm
cxx:
prefer:
- llvm
fortran:
prefer:
- gccon this system:
There is one spec, radiuss.develop.csv 
|
Member
|
with 25%/75% 
|
Member
|
I don't think this is what we want. For a solve with a non-default compiler specified on the root, this will make it even more difficult to get the rest of the stack built with the compiler specified on the root. I think what we need instead is a per-parent penalty on provider duplicates (instead of the current per-duplicate penalty). That will ensure that even when compiler mixing is forced, it won't propagate further up the DAG. |
Member
Author
|
Can you give an example? The issue that was pointed out is exactly |
Member
Author
|
Ping. Can we proceed reviewing this? |
This commit changes how penalties for language virtuals are computed so that a penalty is taken each time a non-preferred compiler is used. Signed-off-by: Massimiliano Culpo <[email protected]>
alalazo
force-pushed
the
bugfix/solver-virtual-preferences
branch
from
108869e to
5a33b90
Compare
Member
tgamblin
approved these changes
Oct 27, 2025
kshea21
pushed a commit
to kshea21/spack
that referenced
this pull request
Nov 4, 2025
This commit changes how penalties for language virtuals are computed
so that a penalty is taken each time a non-preferred compiler is used.
Using this environment as an example:
```yaml
spack:
specs:
- "fftw~mpi %c,fortran=llvm"
packages:
c:
prefer: [gcc]
cxx:
prefer: [gcc]
fortran:
prefer: [gcc]
```
**Before the PR**
Every node uses `clang` as a compiler, since the penalty is taken per
provider, and we force `clang` on `fftw`.
**After the PR**
Only `fftw` uses `clang`, since a penalty is taken per provider use,
so switching other nodes to `clang` is suboptimal (since `gcc` is preferred).
Signed-off-by: Massimiliano Culpo <[email protected]>
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
4 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
This commit changes how penalties for language virtuals are computed so that a penalty is taken each time a non-preferred compiler is used.
Using this environment as an example:
Before the PR
Every node uses
clangas a compiler, since the penalty is taken per provider, and we forceclangonfftw.After the PR
Only
fftwusesclang, since a penalty is taken per provider use, so switching other nodes toclangis suboptimal (sincegccis preferred).