Here are some benchmarks for the image subtraction using <code>ppSub</code>. The inputs are images of a GRB from the Danish 1.5m telescope, which have been registered and trimmed to 541x531 pixels. No input masks or weight maps are used.

<code>ipp003</code> was used for this benchmark. No multithreading, or any other tricks, were used, except that psLib and psModules were compiled with <code>--enable-optimize</code>.

Note that the elapsed time has different dependencies on the kernel size for the two kernel types. That's because the kernel size directly affects the number of parameters in the POIS kernel, while it does not affect the number of parameters in the ISIS kernel (that's set by the specification of three Gaussians modified by polynomials; widths 0.7, 1.5, 3 with polynomial orders 6, 4, 2 respectively throughout these benchmarks).

<pre> # Kernel Spatial Kernel Time # type order half-size (sec)

POIS 0 5 1.4

7 2.57 10 6.66

1 5 4.29

7 20.76

2 5 22.86

ISIS 0 5 5.11

7 6.58 10 9.72

1 5 25.94

7 37.12

2 5 53.01

</pre>