Build Python without build SCIp

[cvancrae]

Hi,
I want to build or-tools for Python with SCIP support but from external build of SCIP.
I use this :
cmake -S. -Bbuild -DBUILD_PYTHON=ON -DBUILD_SAMPLES=OFF -DBUILD_EXAMPLES=OFF -DBUILD_TESTING=OFF -DUSE_SCIP=ON -DBUILD_SCIP=OFF

But it build SCIP.

[sschnug]

Some remarks:

afaik

• or-tools builds SCIP not with it's default lp-solver SOPLEX but with or-tools' GLOP lp-solver
• SCIPs lp-solver implementation cannot be configured at runtime and the lp-solver decision is applied at SCIP compile-time

This "might" complicate some things for you iff or-tools does not support this in the build-config (don't know, did not check).

(Another topic might be the selection/compilation+patches of the symmetry-breaking backend)

Maybe quickly check the CMake as well as SCIP sources in or-tools with this information at hand.

---

Do you have a good reason to bring your own SCIP?

[Mizux]

By default it is not supported, to make a standalone python package we have to ship with SCIP embedded to follow PEP 513..
ref: https://peps.python.org/pep-0513/#the-manylinux1-policy

Here BUILD_DEPS is forced to ON if any BUILD_<LANG> is enable.

or-tools/CMakeLists.txt

Lines 163 to 164 in f676293

	if(BUILD_PYTHON OR BUILD_JAVA OR BUILD_DOTNET)
	option(BUILD_DEPS "Build all dependencies" ON)

or-tools/CMakeLists.txt

Lines 283 to 287 in f676293

	if(USE_SCIP)
	CMAKE_DEPENDENT_OPTION(BUILD_SCIP "Build the SCIP dependency Library" OFF
	"NOT BUILD_DEPS" ON)
	message(STATUS "Build SCIP: ${BUILD_SCIP}")
	endif()

Forced to ON (last param) if expression NOT BUILD_DEPS is false otherwise default to OFF.
see: https://cmake.org/cmake/help/latest/module/CMakeDependentOption.html

BUT you can still hack this code (OSS is good !)
so you may hack this lines to set(BUILD_SCIP OFF) or option(BUILD_SCIP OFF) instead....

we could replace this code by:

if(USE_SCIP)
  if(BUILD_DEPS)
    option(BUILD_SCIP "Build the SCIP dependency Library" ON)
  else()
    option(BUILD_SCIP "Build the SCIP dependency Library" OFF)
  endif()
  message(STATUS "Build SCIP: ${BUILD_SCIP}")
endif()

so user still have option to change the default (sound) value....
ref: https://cmake.org/cmake/help/latest/command/option.html

[cvancrae]

With this modification, I can do exactly what I want.
I think you should modify the CMake file.