Yes, but only when setting MAKEFLAGS from within a Makefile. It appears
the rules do not apply when MAKEFLAGS is set by the invoking shell.
(And actually, current GNU make handles parallel execution differently
on Linux, using a job server that all make subprocesses use to
coordinate execution -- the documentation below is from 1998.)
If you still don't believe :) try putting the following in a Makefile
and running MAKEFLAGS=j3 make
all: r1 r2 r3
r1 r2 r3:
echo rule $@; sleep 5
-Mike
On 09/09/2011 02:55 PM, Jean-Christophe Fillion-Robin wrote:
Reading through make documentation, seems setting -jx to MAKEFLAGS is
a no-op.
/"The `-j' option is a special case (see section Parallel Execution
<http://theory.uwinnipeg.ca/localfiles/infofiles/make/make_47.html#SEC46>).
If you set it to some numeric value, `-j 1' is always put into
|MAKEFLAGS| instead of the value you specified. This is because if the
`-j' option were passed down to sub-|make|s, you would get many more
jobs running in parallel than you asked for. If you give `-j' with no
numeric argument, meaning to run as many jobs as possible in parallel,
this is passed down, since multiple infinities are no more than one. "/
Source: http://theory.uwinnipeg.ca/localfiles/infofiles/make/make_53.html
Jc
On Fri, Sep 9, 2011 at 3:37 PM, Mike Wittman
<[email protected] <mailto:[email protected]>>
wrote:
If you are building on Linux, try
MAKEFLAGS=j8 make distcheck
I have successfully used the MAKEFLAGS environment variable to
propagate parallel build invocations through scripts that invoke
make with fixed options.
-Mike
On 09/09/2011 09:21 AM, Clifford Yapp wrote:
I can finally give a good concrete case where I might need to do
this (or need some other very clever solution).
I have created a distcheck command for BRL-CAD that has a lot of
responsibilities, including doing a complete configure and build
of BRL-CAD from a source archive expanded from a CPack tarball.
The distcheck rule uses cmake to fire off the build (this is to
try and be future proof against using other tools than Make to do
a distcheck) but I need to pass the parallel build setting -j
from Make down to the ${CMAKE_COMMAND} build launched by the
distcheck rule, and there doesn't seem to be any way to do it.
This is the subset of the distcheck rule (somewhat edited for
clarity):
ADD_CUSTOM_TARGET(distcheck
COMMAND ${CMAKE_COMMAND} -E echo "Stage 1: Create source
tgz, tbz2 and zip archives from toplevel archive."
COMMAND cpack --config
${CMAKE_CURRENT_BINARY_DIR}/CPackSourceConfig.cmake
COMMAND ${CMAKE_COMMAND} -E echo "Stage 2: Expand tgz
archive and prepare to build from archive sources."
COMMAND ${CMAKE_COMMAND} -E tar xvzf
${CPACK_SOURCE_PACKAGE_FILE_NAME}.tar.gz
COMMAND ${CMAKE_COMMAND} -E make_directory
_${CPACK_SOURCE_PACKAGE_FILE_NAME}-build
COMMAND ${CMAKE_COMMAND} -E make_directory
_${CPACK_SOURCE_PACKAGE_FILE_NAME}-install
COMMAND ${CMAKE_COMMAND} -E chdir
_${CPACK_SOURCE_PACKAGE_FILE_NAME}-build ${CMAKE_COMMAND}
../${CPACK_SOURCE_PACKAGE_FILE_NAME}
-DCMAKE_INSTALL_PREFIX=${CMAKE_CURRENT_BINARY_DIR}/_${CPACK_SOURCE_PACKAGE_FILE_NAME}-install
COMMAND ${CMAKE_COMMAND} -E echo "Stage 3: Compile using
source from tgz archive."
COMMAND ${CMAKE_COMMAND} --build
_${CPACK_SOURCE_PACKAGE_FILE_NAME}-build
)
This can be successfully fired off by "make distcheck", which is
the desired behavior. However, the --build option doesn't
respect (naturally) any -jN options fed to make, since they
aren't specified at CMake time when the distcheck Makefile target
is being generated.
Perversely enough, if I'm understanding the issue correctly I
won't be able to use the -jN value itself in any case, even if
the Makefile can be taught to do something smart:
http://old.nabble.com/MAKEFLAGS-var-does-not-show-%22-j%22-param-----td15983337.html
The best idea I can come up with so far is for the CMake
generated Makefile to write out a variable containing some CPU
related variable (e.g. make CPUS=8 and write the value of $(CPUS)
to CMakeFiles/make_cpu_flag or some such) and then convert the
distcheck commands above into a series of EXECUTE_PROCESS lines
in a rundistcheck.cmake file that is launched by the distcheck
rule with a ${CMAKE_COMMAND}. In rundistcheck.cmake, I can check
for the presence of the make_cpu_flag file and if found add the
-j parallel flag to the --build line before running it. That
will mean a parallel distcheck will have to use a different make
syntax than the standard make -j, but at least it would be
something. Unfortunately, that means I still need the Makefile
to let me know what was passed in up front, which means tweaking
the CMake generated output somehow (not really sure how yet).
Does anybody else have a mechanism for passing parallel build
instructions from make down to child ${CMAKE_COMMAND} --build
instances?
Cheers,
CY
On Wed, Feb 2, 2011 at 4:32 PM, Michael Hertling
<[email protected] <mailto:[email protected]>> wrote:
On 02/02/2011 03:34 PM, Clifford Yapp wrote:
> Is there any way to customize the Makefile output from CMake to
> include user-defined lines (say, something like "#include
> Makefile.inc") at the end of each Make file?
[snip]
However, this approach is neither portable nor clean
nor <your-expectation-here>, so I would ask Eric's questions,
too. ;)
Regards,
Michael
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