Multiple cores are the norm now for chip-makers, though application
developers don’t always develop in ways that take advantage of more than one
processor core. How do you bridge the divide?
Intel thinks the key is by making a cornerstone development tool for parallelism open source. To that end Intel is open sourcing Intel Threading Building Blocks (TBB) under the GPL version 2
TBB is a method of programming for C++ for parallelism that Intel has offered for over a year. With version 2.0 they’re open sourcing it and making it available on more operating systems and processors.
James Reinders, chief evangelist and director of marketing for Intel software
development products, told internetnews.com that there were some
concerns with the 1.x version of TBB that open sourcing will help to
alleviate.
“Customers were concerned that Intel might decide to quit selling it [TBB] one day,” Reinders said.
“Open sourcing addresses the issue and paves the way for TBB to be
accessible for every C++ user to use on every platform that they care
about.”
Reinders explained that TBB works with nearly all C++ compilers and
enables developers to take advantage of parallelism without the need to move
from a familiar environment. TBB 2 also attempts to simplify programming for
multiple processors by abstraction. Rather than trying to write threads that
execute on a particular processor core, TBB handles parallelism based on
task.
Taking advantage of TBB is relatively straightforward, too. Reinders noted
that TBB is a template library. In the part of the program where you want
some parallelism you use a template.
A template looks like a function call,
but in C++ a template is expanded and compiled particular to the types that
you are giving it. TBB also helps with multi-core memory allocation, as well
as task allocation with the inclusion of a scalable memory allocator.
There is no hard limit now for how many cores TBB can scale to with Intel
seeing good results on both 8 and 16 cores. That said, Reinders speculated
that TBB was not ready for 100 cores.
“Once you start getting into a really large machine, you need to pay more
attention to how the data is distributed, because if the data is shuffled
back and forth across processors, the costs go up,” Reinders said. “TBB
doesn’t try to address data partitioning directly.”
Though Intel is open sourcing TBB, it is not open sourcing all of its
multi-core programming tools. In particular Thread Profiler 3.0 and Thread Checker 3.0, which were introduced last August, will stay as proprietary products. Reinders explained that Intel has
invested its time and energy into open sourcing TBB first and first want to
build a community around it.
In addition to open sourcing the TBB tools, Intel is launching a site called Threading Building Blocks, which is intended to be a community-oriented
site surrounding TBB usage and development. Reinders noted that Intel will
be accepting contributions to the project, though at launch the site will not
have a full versioning control system in place.
Intel considered going with either Apache or Eclipse instead of trying to
run the TBB project itself but ultimately decided to go it on their own.
“We wanted a place where parallelism is a passion,” Reinders said.
“Ultimately we decided it would work best if we took that role and ran as
our own project. Eclipse or Apache was decided to be not the best route to
take though we’re not closed to thinking about it. But right now we’re
committed to running it ourselves and making sure it has a passionate
parallelism.”
Though TBB is now open source, Intel will actually be licensing the effort
under both the GPL 2 and a commercial license. Any committers to the project
will give copyright back to the project. The dual-licensing approach,
according to Reinders, will allow existing commercial users to continue using
TBB while opening up TBB to open source.
Choosing the GPL version 2 is also a key part of how Intel hopes to grow
TBB.
“The biggest appeal of GPLv2 is that it is well known, understood and widely
used,” Reinders said. “We discussed coming up with our own license or using
another and at the end of the day we thought it best to go with what is well
accepted in the industry.”
GPL version 3 was officially released on June 29 and was also considered by Intel. Reinders noted
that Intel felt more comfortable with understanding what GPL v2 means, though
he did state that Intel is now taking an active look at GPL version 3.
