About an hour

Are compile times for projects constant? We like to think that a faster compute will give us better performance, including faster build times. (Those of us with the title "Buildmaster" are very conscious of performance and we constantly tune the build environment.) Yet the evidence does not support the claim.

Many moons ago, I worked on a project that was built in C (yes, C and not C++) and ran under MS-DOS. The source was about 65,000 lines of code (I know because I measured it) and it took about an hour to build (I know because I ran the build). This was in 1992, and we used PCs with Intel 80386 processors running at 25 MHz. Keep that figure of "an hour" in mind.

A few moons ago (not so many as "many moons ago), I worked on a project that was built in C++ and ran under Windows. The source was 750,000 lines of code and the build time was about an hour. This was in 2007; our PCs had Intel Pentium whatever processors running at 500 MHz.

Currently I am working on a project that builds in C++ and runs under Windows. The source is about 200,000 lines of code and build time is ... about an hour. Our PCs are Intel Pentium whatevers and running at 850 MHz. The performance "drop" from the previous project to this project may be due to two things: our use of STL and our build environment. STL and the use of templates places an additional load on the compiler, essentially expanding templates and creating code that is not visible to the programmers. Our environment uses servers for storage, not local disks, so reads and writes must travel "across the wire".

So across a span of almost twenty years, the hardware has improved but build times remain at a fixed time. How can this be?

Here are my thoughts:

Our systems are larger Code size has increased. Larger code takes longer to compile. (And to write, and to debug, and to maintain... but that is another discussion.)

Our languages are more complex The simple code of twenty years ago (mostly C) has been replaced with the more complex languages of C++, Java, and C#. More complex languages require more complex compilers.

Our environments are more complex The (relatively) simple build environment of a PC running MS-DOS 5.0 and some NetWare drivers has morphed into a the complex workstation environment of a PC running Windows with its multitude of services and processes, all competing for processing time. In addition, the authorization model has changed, with current systems talking to the central controller for confirmation of access to each and every file operation.

One interesting thing is the hour time frame. There may be psychology involved here. Perhaps we accept an hour as a reasonable amount of time to build something of perceived value. We (as a group) will let build times increase, until they reach the threshold of an hour. At that point, we look to improve the build process.

In the future, I expect the trends to continue. I expect our platforms to become more complex. I expect virtualization and the cloud to play a role in builds. (A few companies have had cloud-like build technologies for years.) People have been developed new source-control systems that are distributed and not centralized. We have new languages such as C# and Ruby. The Agile Development proponents have pushed for smaller systems and automated tests.  ll of these will affect the time it takes to build the system.

And I also expect build times to remain at... about an hour.