The speedup is not necessarily gained from the use of more than one processors.
For instance, in the case of ISPC, $\text{speedup (with ISPC)} = \frac{\text{execution time (without ISPC)}}{\text{execution time (with ISPC)}}$.
The speedup is not necessarily gained from the use of more than one processors.
For instance, in the case of ISPC, $\text{speedup (with ISPC)} = \frac{\text{execution time (without ISPC)}}{\text{execution time (with ISPC)}}$.