Nr of links is constant for the REAL generator

[henrikingo]

Hi Mark

I realize this is not very actively maintained, but recording this here while I'm deep diving into Linkbench a little. Comments on options for fixing this are welcome.

For development purposes, and maybe other reasons, I want to run quicker runs of Linkbench. I can make load phase quicker by loading less data. If I set maxid1 = 10001 I get a smaller nodetable and counttable. However, the load phase then continues to insert 44M records to linktable. This also means there will be on average thousands of links per node, which is probably not a good model of reality.

It appears the default links generator nlinks_func = real isn't configurable at all. Should it be? Maybe is should automatically adapt to maxid1 so that it always generates about 4 links per node?

I can workaround this issue by using another nlinks_func:

nlinks_func = com.facebook.LinkBench.distributions.ZipfDistribution
nlinks_shape = 1.5
nlinks_mean = 2

[mdcallag]

I have no experience with nlinks_func=real, but not adapting to maxid1 sounds like a bug. I am happy to take a pull request.