I have a bunch of commands I would like to execute in parallel. The commands are nearly identical. They can be expected to take about the same time, and can run completely independently. They may look like:
command -n 1 > log.1
command -n 2 > log.2
command -n 3 > log.3
...
command -n 4096 > log.4096
I could launch all of them in parallel in a shell script, but the system would try to load more than strictly necessary to keep the CPU(s) busy (each task takes 100% of one core until it has finished). This would cause the disk to thrash and make the whole thing slower than a less greedy approach to execution.
The best approach is probably to keep about n tasks executing, where n is the number of available cores.
I am keen not to reinvent the wheel. This problem has already been solved in the Unix make program (when used with the -j n option). I was wondering if perhaps it was possible to write generic Makefile rules for the above, so as to avoid the linear-size Makefile that would look like:
all: log.1 log.2 ...
log.1:
command -n 1 > log.1
log.2:
command -n 2 > log.2
...
If the best solution is not to use make but another program/utility, I am open to that as long as the dependencies are reasonable (make was very good in this regard).
See pattern rules
Another way, if this is the single reason why you need make, is to use -n and -P options of xargs.