modified fig_3_11_depends_on doesn't work with multi cores

[jnorwood]

I modified fig_3_11_depends_on to further test it, since the example didn't display anything that could show its execution. I am providing a modified version that uses event.wait() for each event. It creates the expected results.

I've left in the commented out depends_on statements. If I uncomment those and comment out the event.wait() statements, the results are not as expected.

Also, in general, I don't see an example to use the depends_on with the execution blocks rearranged. I tried by creating event objects at the entry of main, but I see no example to set these events in an initial state or to have the event objects updated without an assignment that would overwrite the address of the object.

I'm going to attach my modified example
fig_3_11_depends_on.zip

I'm using the oneapi docker installation on ubuntu 20.04, and building the examples with cmake generated makefiles, but with -O0 optimizations.

[jnorwood]

does depends_on only search for events associated with the current queue context?