Hi,
I have 8 HashMaps distributed over 8 places with the PlaceLocalHandle
functionality. I am trying to merge the contents together into place 0. I
have two implementations. The first is the brute forced way where I insert
all the entries from HashMaps at other places into the HashMap at place 0:
finish for(i = 1; i < places; i++)
{
async(Place.places(i))
{
for(e in hashmap.entries())
{
val key = e.getKey();
val value = e.getValue();
async(Place.places(0))
{
hashmap.insert(key, value);
}
}
}
}
The second way, I am attempting to implement a global reduction of merging
the HashMaps, it would look something like this:
initial HashMaps at Places: 0 1 2 3 4 5 6 7
I have a function similar to the one above that merges 4 to 0, 5
to 1, 6 to 2 and 7 to 3.
I will be left with HashMaps at Places: 0 1 2 3 since 4,5,6,7 have
been merged into them.
Thereafter, I do the same with 2 to 0 and 3 to 1. And finally
merging 1 to 0. I do this recursively until place 0.
When I was testing the performance of these two implementations, I initially
thought that the global reduction method would outperform the brute forced
way. However, the results showed that the brute force way was usually 2x ~
3x times faster than the global reduction method. Would anyone have any idea
as to why the results are like this? The code for the global reduction is
similar to the brute forced in the way it gets the entries and inserts them
into the HashMaps.
Thanks,
Han
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