Chiheng Xu wrote:
On Tue, Aug 3, 2010 at 2:51 PM, Tim Murphy<tnmur...@gmail.com> wrote:
Since some things happen at the same time there is no single "serial
order". The semaphore mechanism, forces one of the possible orders.
I'm not familiar with source code of make, but I believe the "serial
order" of shells is determined by the dependence DAG, it may be
unique for a given dependence DAG.
Shells can be issued and completed at random order(only need
satisfying the dependence relation). But make can print their outputs
strictly in their "serial order".
I'm trying very hard to only provide constructive comments in response to this
thread, but frankly this is, in a word, stupid.
If you want make's output to be in serial order, then don't use parallel make
at all. The point to parallel make is that it allows jobs which have no
ordering dependency to run in parallel. If you want their output to be fully
serialized, then you will force make to wait for them to complete serially.
Which automatically also means that make will have to maintain an arbitrarily
large internal queue for all of the output, because given the unpredictable
completion times of multiple jobs running concurrently, no output can be
emitted until the slowest parallel job completes. In particular, if you have
recursive makefiles, no parent make process can output anything at all until
all of its submakes have completed, because no individual make process has
enough knowledge about what the actual serial order is.
Given that this discussion seems to have arisen due to the braindead stdio
handling in Cygwin, it seems like any de-mangling of parallel make's output
should be directed to the Cygwin libraries. In my experience Cygwin is too
slow an environment to be useful anyway, which is why I use MSYS for Windows
builds. But I have to admit, I only use it inside a single-core VirtualBox
these days so I haven't looked at how parallel make behaves there. But the
fact is all I/O in Cygwin is funneled through the Cygwin DLL, so there's no
reason that it can't be fixed to not mingle/mangle lines from different
processes together. But again, that's not gnu-make's problem, that's a Cygwin
issue.
--
-- Howard Chu
CTO, Symas Corp. http://www.symas.com
Director, Highland Sun http://highlandsun.com/hyc/
Chief Architect, OpenLDAP http://www.openldap.org/project/
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