About .NOTPARALLEL

[Peng Yu]

Hi,

`.NOTPARALLEL'
     If `.NOTPARALLEL' is mentioned as a target, then this invocation
     of `make' will be run serially, even if the `-j' option is given.
     Any recursively invoked `make' command will still run recipes in
     parallel (unless its makefile also contains this target).  Any
     prerequisites on this target are ignored.

According to the above explanation form the manual, it seems that the
behavior of the following makefile should be that all the four .txt
files should be generated in series when -j is used.

#################
.PHONY: all clean

all: a.txt b.txt c.txt d.txt

.NOTPARALLEL:

%.txt:
        sleep 2; touch $@

clean:
        $(RM) *.txt
##################

However, I think the syntax of .NOTPARALLEL can be improved a little.
For example, I'd like the a.txt and b.txt are not generated in
parallel with anything other .txt files, but c.txt and d.txt be
generated in parallel, when '-j' option is used. Currently the
following Makefile is essentially the same as the above one. May I
suggest to add this syntax to make?

##################
.PHONY: all clean

all: a.txt b.txt c.txt d.txt

.NOTPARALLEL: a.txt b.txt

%.txt:
        sleep 2; touch $@

clean:
        $(RM) *.txt
###############

-- 
Regards,
Peng