3.2.2 Productivity
Keywords: perfbook_html

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3.2.2 Productivity

Quick Quiz 3.8: Why all this prattling on about non-technical issues??? And not just any non-technical issue, but productivity of all things? Who cares? End Quick Quiz

Productivity has been becoming increasingly important through the decades. To see this, consider that early computers cost millions of dollars at a time when engineering salaries were a few thousand dollars a year. If dedicating a team of ten engineers to such a machine would improve its performance by 10%, their salaries would be repaid many times over.

One such machine was the CSIRAC, the oldest still-intact stored-program computer, put in operation in 1949 [Mus04,Mel06]. Given that the machine had but 768 words of RAM, it is safe to say that the productivity issues that arise in large-scale software projects were not an issue for this machine. Because this machine was built before the transistor era, it was constructed of 2,000 vacuum tubes, ran with a clock frequency of 1kHz, consumed 30kW of power, and weighed more than three metric tons.

It would be difficult to purchase a machine with this little compute power roughly sixty years later (2008), with the closest equivalents being 8-bit embedded microprocessors exemplified by the venerable Z80 [Wik08]. This CPU had 8,500 transistors, and can still be purchased in 2008 for less than $2 US per unit in 1,000-unit quantities. In stark contrast to the CSIRAC, software-development costs are anything but insignificant for the Z80.

Figure: MIPS per Die for Intel CPUs

The CSIRAC and the Z80 are two points in a long-term trend, as can be seen in Figure . This figure plots an approximation to computational power per die over the past three decades, showing a consistent four-order-of-magnitude increase. Note that the advent of multicore CPUs has permitted this increase to continue unabated despite the clock-frequency wall encountered in 2003.

One of the inescapable consequences of the rapid decrease in the cost of hardware is that software productivity grows increasingly important. It is no longer sufficient merely to make efficient use of the hardware, it is now also necessary to make extremely efficient use of software developers. This has long been the case for sequential hardware, but only recently has parallel hardware become a low-cost commodity. Therefore, the need for high productivity in creating parallel software has only recently become hugely important.

Quick Quiz 3.9: Given how cheap parallel hardware has become, how can anyone afford to pay people to program it? End Quick Quiz

Perhaps at one time, the sole purpose of parallel software was performance. Now, however, productivity is increasingly important.