Building all of Boost in a few minutes

Question

Can anyone explain why following these instructions:

http://www.boost.org/doc/libs/1_59_0/more/getting_started/unix-variants.html#easy-build-and-install

... it takes my decent machine 5 hours to build all of Boost, while some folks report doing the same in only 3 minutes ?

Is there another way to build Boost than the one mentioned above that indeed goes pretty quickly (compared to several hours, at any rate).

I am using the Clang compiler on Darwin (Mac) option. Not sure how relevant it is but I have 16 GB RAM and a recent SSD. The clock is 2.3 Ghz.

Edit: I'm happy to report, based on the comments and answers, that using the ./b2 -j4 -d0 options, I got my compilation time down to 13 minutes. Also the -jN option is not listed in the set of available options with the default --help, you must instead call --help-options to see these additional more "advanced" techniques.

Answer 1

I just ran a few tests with a few different build configs.

Hardware: 2012 MacBook Pro (2.3Ghz Ivy Bridge i7 [i7-3615QM]), factory SSD and 16GB of ram.

Software: Mac OS X 10.11.1 with Xcode 7 (Apple LLVM version 7.0.0 clang-700.1.76). Fresh copy of Boost 1.59.0 from the website.

I tested the following build commands:

Default Build:

./bootstrap.sh && ./b2 -j N

Build forcing the linking of libc++

./bootstrap.sh && ./b2 toolset=clang cxxflags="-stdlib=libc++" linkflags="-stdlib=libc++" -j N

For each I tried three different values for N: 1 (single thread), 4 (matching physical cores), and 8 (matching hyperthreaded cores).

Default linking:

• With 8 the build time was 6:45 minutes
• With 4 the build time was 7:22 minutes
• With 1 the build time was 22:58 minutes

Linking libc++:

• With 8 the build time was 4:35 minutes
• With 4 the build time was 5:45 minutes
• With 1 the build time was 17:15 minutes

Conclusion: Boost shouldn't have to take all day to build on a multi-core system with an SSD even if it isn't brand new. Building with the default (singled thread) does take way longer than a parallel build. The Boost build with clang on OS X does benefit slightly from hyperthreading. Linking with libc++ seems a bit faster as well.