Effective Bandwidth Calculation

Effective bandwidth is calculated by timing specific program activities and by knowing how data is accessed by the program. To do so, use this equation:

Effective bandwidth = ((Br + Bw) / 109) / time

Here, the effective bandwidth is in units of GBps, Br is the number of bytes read per kernel, Bw is the number of bytes written per kernel, and time is given in seconds.

For example, to compute the effective bandwidth of a 2048 x 2048 matrix copy, the following formula could be used:

Effective bandwidth = ((20482 x 4 x 2) / 109) / time

The number of elements is multiplied by the size of each element (4 bytes for a float), multiplied by 2 (because of the read and write), divided by 109 (or 1,0243) to obtain GB of memory transferred. This number is divided by the time in seconds to obtain GBps.