Improve the documentation of parallel builds.

Not all users are familiar with the -j or --jobs flags for make and the
current explanation is buried in the middle of several other notes. We
can make this simpler by showing how to parallelize the build
explicitly.

diff --git a/doc/readme.html b/doc/readme.html
index 6c35741edd11ca7bd6bfc3112805f9d9837e6a3b..8daf1299d9532d1380be4553ceede752e77ee9fc 100644 (file)
--- a/doc/readme.html
+++ b/doc/readme.html
@@ -161,15 +161,19 @@
 
     <p>
         <acronym>deal.II</acronym> uses the
-        <a href="http://www.cmake.org/" target="_top">CMake</a> integrated configuration and build system. Unpacking will create a subdirectory <tt>deal.II/</tt> in the current directory. Then do the following steps:</p>
+        <a href="http://www.cmake.org/" target="_top">CMake</a> integrated configuration and build system. Unpacking will create a subdirectory <tt>deal.II/</tt> in the current directory. Then do the following steps to configure the build process:</p>
 
     <pre>
   mkdir build
   cd build
   cmake -DCMAKE_INSTALL_PREFIX=/path/to/install/dir ../deal.II
-  make install
+    </pre>
+    We recommend compiling deal.II in parallel if your machine has more than one processor core. This can be done by providing the <code>--jobs</code> flag to <code>make</code> with a numerical argument. Here we compile with four <code>make</code> jobs:
+    <pre>
+  make --jobs=4 install
   make test
     </pre>
+    One should usually use one job for each processor core on the machine.
 
     <p>
         These steps compile, link, install the deal.II library, and run a few consistency checks. The whole process should take between a few minutes and an hour, depending on your machine.
@@ -182,9 +186,7 @@
             Another option is to use something like <code>`pwd`/../installed/</code> (note the backticks). Make sure the installation directory is not the same as the location where you unpacked <tt>deal.II/</tt>.
         </li>
 
-        <li> If your machine has multiple processors, use <code>make
-         -jN install</code> in the second to last step instead, where <code>N</code> is the number of simultaneous build processes you want <code>make</code> to use at any given time. Allowing <code>make</code> to use more simultaneous build processes (assuming you have that many processor
-            cores) will greatly lower the build time. <code>make test</code> automatically runs in parallel and no <code>-jN</code> flag should be supplied to it.
+        <li> <code>make test</code> automatically runs in parallel and no <code>-jN</code> flag should be supplied to it.
         </li>
 
         <li> If you do not intend to modify the <acronym>deal.II</acronym> sources and recompile things, then you can remove the <code>build/</code> directory after the last step.