Threaded C++ site update on FreeBSD

[jteresco]

When threading is enabled, compiling with g++ on noreaster, the following run-time error occurs:

ld-elf.so.1: /usr/local/lib/gcc5/libstdc++.so.6: version GLIBCXX_3.4.22 required by /tm-tmpfs/travelmapping/DataProcessing/siteupdate/cplusplus/siteupdate not found

[yakra]

I've just had a handful of successful runs (compiled with clang++) on noreaster, testing out as many as 8 threads.
HighwayData @ 27a625459516a8f5c53f73a24ce51416ab991677
UserData @ 3ec63996d33e499027a3d4c8f47abc0d3ce7659f

Some times for a few select tasks:

task	1 thread	4 threads	8 threads
Searching for near-miss points	2.9	0.7	0.4
Processing traveler list files	13	3.5	2
Augmenting travelers for detected concurrent segments	5.4	1.4	0.7
Computing stats per traveler	6.7	1.8	1.6
Creating per-traveler stats logs and augmenting data structure	28.3	8.5	6.7
total time @ ErrorList abort	195.8	125.7	123.4

Things seemed to slow down a bit on the bits that require more disk access, such as Reading waypoints for all routes and Writing near-miss point merged wpt files. @jteresco, I can see why you got that SSD. :)

Subgraph generation took about 38s even when I wrote the files to /dev/null. What this tells me is that httpd, mysqld, student programs, and whatever else keep the system busy enough to not leave as much L3 cache & memory bandwidth for siteupdate.

There's a catch, though.
A devilishly weird, obscure-but-reproducible little bug.
More to come at #375...

[yakra]

#407 closes this. The threaded version will compile & run on noreaster.
Other remaining issues:

• clang/FreeBSD-friendly makefile
• Concurrent segment detection crashes