HP XC System 2.x Software User Manual

Page 51

single compilation line, so it is common to talk about concurrent compilations, though GNU

make

is more general.

On non-cluster platforms or command nodes, matching concurrency to the number of processors
often works well. It also often works well to specify a few more jobs than processors so that one
job can proceed while another is waiting for I/O. On an HP XC system, there is the potential to
use compute nodes to do compilations, and there are a variety of ways to make this happen.

One way is to prefix the actual compilation line in the rule with an

srun

command. So, instead

of executing

cc foo.c -o foo.o

it would execute

srun cc foo.c -o foo.o

With concurrency, multiple command nodes would have multiple

srun

commands instead of

multiple

commands. For projects that recursively run

make

on subdirectories, the recursive

make

can be run on the compute nodes. For example:

$ cd subdir; srun $(MAKE)...

Further, if the recursive make is run remotely, it can be told to use concurrency on the remote
node. For example:

$ cd subdir; srun -n1 -N1 $(MAKE) -j4...

This can cause multiple makes to run concurrently, each building their targets concurrently.
The

-N1

option is used to reserve the entire node, because it is intended to be used for multiple

compilations. The following examples illustrate these ideas. In GNU

make

, a

$(VARIABLE)

that is unspecified is replaced with nothing. Therefore, not specifying

PREFIX

keeps the

original makefile’s behavior, but specifying

PREFIX

to appropriate

srun

command prefixes

will cause concurrency within the build.

For more information about GNU parallel

make

, refer to the

make

manpage. For additional

sources of GNU information, refer to the references provided in About This Document.

In this section, three different ways to parallelize a make procedure are illustrated. The

smg98

package is used to illustrate these three procedures. The

smg98

package is available at the

following URL:

http://www.llnl.gov/asci/applications/SMG98README.html

These procedures take advantage of the GNU

make -j

switch, which specifies the number of

jobs to run simultaneously. Refer to the

make

manpage for more information about this switch.

The following parallel make approaches are described:

•

Section 3.9.1.1 — Go through the directories serially and have the make procedure within
each directory be parallel. (Modified makefile:

Makefile_type1

•

Section 3.9.1.2 — Go through the directories in parallel and have the make procedure
within each directory be serial (Modified makefile:

Makefile_type2

•

Section 3.9.1.3 — Go through the directories in parallel and have the make procedure
within each directory be parallel (Modified makefile:

Makefile_type3

The original makefile is shown below:

#BHEADER***********************************************************

The Regents of the University of California

# See the file COPYRIGHT_and_DISCLAIMER for a complete copyright

# notice, contact person, and disclaimer.

# $Revision: 1.1 $

#EHEADER***********************************************************

SHELL = /bin/sh

Developing Applications

3-11