Accelerating MATLAB Performance

165MATLAB

®

-Specic Techniques

It should be noted that while the numerical complexity may decrease, in some cases this

may come at the expense of increased memory usage. This is not always the case. In fact,

in our example above, the temporary matrix created by B*C is 200×400 (or 625 KB), which

is signicantly smaller than the temporary matrix for A*B (300×10000, or 23 MB). This may

be the reason that the speedup we received (~2.3) was slightly faster than the theoretical

expected value (2.2). As the matrices size increases, so too does the impact of the memory

effect (also see Chapter 9).

The effect of multiplication order increases when the multiplicands have signicantly

different dimension sizes. This is the case when matrices are multip ...