• Problem statement and some experimentation
• Explanation of the algorithm I came up with in 2021.
• Recursive merge sort algorithm to have something to compare
• Re-using linked lists while bench marking
• Effect of address-ordered linked lists
• Traversing linked lists does not exhibit weird performance drops at specific list lengths
• Effect of size of linked list nodes tests whether virtual memory is somehow involved. It is not.
• Bottom-up implementation with linked lists from Wikipedia, has the same performance drops as my July 2021 algorithm
• Memory access effects: incrementing .Data values, or arbitrarily changing .Next pointers does not cause the performance drops, and looking for other anomalies
• Effect of garbage collection before preparing a new, unsorted, linked list
• The memory access patterns of recursive and wikipedia bottom up algorithms are identical. The performance is not.
• I wrote an iterative, explicit stack frame variation of recursive mergesort to try to get the same abrupt performance drops as the wikipedia bottom up algorithm. No joy.

I wrote variants of recursive mergesort that simulate function call recurision by iteration with an explicit stack of activation records. This is an effort to try to understand the abrupt performance drops that the wikipedia bottom up algorithm exhibits at some linked list lengths.

Incidentally, these two algorithms both satisfy the Daily Coding Problem problem statement. Their simulated call stack could potentially overflow for extremely long lists, but those stacks wouldn’t have to be much bigger to accomodate those long lists.

When I last had problems with PPP, I noticed that some non-routeable IP addresses ended up getting sent out for DNS reverse lookup.

This is different than routing packets with those same (nominally) non-routeable addresses out into The Internet.

I finally looked at the addresses of linked list nodes that my recursive and wikipedia bottom-up) algorithms read and write.

We use incredibly weak language around smartphones and point-n-click computer interfaces. It’s embarrassing.

There’s a system admin saying: It’s always DNS

But weird problems aren’t always DNS problems. Better than 50% of the time, they’re cabling problems.

I went to see the Union Pacific No. 4014, a Big Boy locomotive, at a whistle stop in Greeley, CO, October 23, 2024.

I had to get my production server to clamp MSS (size of TCP data “segment” in bytes) to path MTU.

Model rocketry changed my life back in the 1970s. I built my first rocket, an Estes Big Bertha the summer between 3rd and 4th grade, which I think was the summer of 1970.