Wednesday, October 9, 2013

Local Supermarkets

Early this year one of the supermarkets near my townhouse, the Super Fresh in Plainsboro, closed.  This didn't bother me much as I think I had only shopped there once.  However this week I learned the Stop&Shop a few miles up Route 1 is also going to close.  This is more bothersome as I had shopped there fairly often and will miss it.  According to the article at the Stop&Shop link there are plans to build a Shop-Rite supermarket a bit south on Route 1 (which would be closer to me) so maybe things will eventually work out for the better.

Apparently the Stop&Shop is the third supermarket to fail at that spot in a 20 year period.  This is a bit surprising as it seems like a good location with easy access to Route 1.   But perhaps the population density in the immediate vicinity is not as high as it could be.  I hadn't seen any indications of distress at the store, although in hindsight perhaps the fact that (at least at the times I was there) most of the checkout stations did not need to be staffed was a bad sign.    

Monday, October 7, 2013

The Signal and the Noise

I recently read "The Signal and the Noise" by Nate Silver.  Nate Silver became well known because of the political analysis and generally accurate election predictions in his blog 538.  Earlier he had developed a successful system, PECOTA, for predicting the development of minor league baseball players.  In this book he attempts a general survey of forecasting.  I found the book a bit disappointing (perhaps in part because I had excessively high expectations).

One problem with the book is that when Silver moves away from his specific areas of expertise he makes mistakes showing he has failed to completely grasp the material.  On page 110 Silver writes:

... They are hot: the 77 trillion calculations that the IBM Bluefire supercomputer makes every second generate a substantial amount of radiant energy.  They are windy: all that heat must be cooled, lest the nation's ability to forecast its weather be placed in jeopardy, and so a series of high-pressure fans blast oxygen on the computers at all times.  ...

Here "radiant energy" is at best a confusing way of saying heat.  And I had never heard of oxygen (as opposed to simple air) cooling.  In any case according to NCAR:

Bluefire relies on a unique, water-based cooling system that is 33 percent more energy efficient than traditional air-cooled systems. Heat is removed from the electronics by water-chilled copper plates mounted in direct contact with each POWER6 microprocessor chip. ...

The chess diagram on page 271 is obviously wrong (the pawn on g2 should be on g3) and the related statement on page 270:

These databases relied on the assumption, however, that Kasparov would respond as almost all other players had when faced with the position, by moving his knight back out of the way. ...

is simply false, the usual move is bg2, retreating the knight would be very weak.

On page 374 Silver writes:

The greenhouse effect is the process by which certain atmospheric gases - principally water vapor, carbon dioxide (CO2), methane and ozone - absorb solar energy that has been reflected from the earth's surface.  ...

Here "reflected" should be "absorbed by and re-radiated".  The key point is because the sun is hotter than the earth solar radiation has shorter wavelengths than the earth's heat radiation.  Greenhouse gases absorb more strongly at longer wavelengths hence block more of the outgoing radiation as compared to the incoming solar radiation.  The effect is to warm the earth's surface.  On the other hand sunshine reflected from the earth's surface remains shortwave and leaves as easily as it arrived.

These (and other similar) errors aren't critical to Silver's arguments and could be fixed without too much trouble but they diminish the reader's general confidence in the author's reliability.  Silver would have done better to have had subject matter experts check for this sort of thing. 

The book has other problems.  At 454 pages it is quite long and there are things like the chapter on the Kasparov - Deep Blue match which could have been cut without too much loss. 

I didn't care for the analysis of the failure of the rating agencies prior to the recent financial crisis.  Silver discusses technical issues but the real problem is the agencies are paid by the people selling the securities they are rating.  This gives them an obvious incentive to fudge their ratings.  Silver understands this when it comes to political polling, polls paid for by a candidate will generally report more favorable results for the candidate than neutral polls.  In the case of political polls the amount of fudging is limited by the existence of neutral and opposition polls.  There were few such countervailing forces when it came to rating complex mortgage backed securities and the rating agency fudging got totally out of hand.  At the end nearly worthless securities were being given AAA ratings.  Silver largely ignores the bad rating agency incentives which remain in place and seem likely to cause similar problems in the future.

I don't want to be too negative, the book contains some interesting material and I agree with a lot of Silver's conclusions.  But I can't really call it a must read.      

Tuesday, October 1, 2013

Yarnell Hill Fire

On June 30, 2013 a crew of 19 firefighters was killed by the Yarnell Hill Fire near Yarnell Arizona.  Recently a report was released on an investigation of this event.  In my view the report is seriously flawed, showing an undue reluctance to criticize the decisions that led to 19 deaths.  The report claims it is trying to avoid hindsight bias, the tendency to label decisions as wrong when they work out badly even if they were actually reasonable under the circumstances.  This is a commendable goal but it has to be balanced against the need to identify avoidable mistakes.  Simply refusing to judge decisions is not the proper balance.

The report refers to decisions made by the crew and speculates about the thinking behind them.  But I expect the crew as a whole was not making decisions, instead the decisions were made by the crew's leaders (who appear to have been two men which the report does not name).  If 19 people are killed in plane crash the investigation will naturally focus on the pilots.  What was their training, experience, reputation?  Similarly one would expect this report to discuss the background of the fire crew leadership but in fact it provides no information at all.  Also in recent years there has been much attention paid to cockpit dynamics.  For example if the pilot makes a mistake does the co-pilot feel free to object.  Again this report does not discuss the analogous fire crew dynamics at all.      

The fire crew was killed while apparently attempting to move from one safe area to another (perhaps as the report speculates because they felt the second area would leave them better positioned for further firefighting efforts, although it should be noted the overall leadership did not expect or particularly want them to do this).  In doing so they chose a route that placed them in mortal danger.  Initially they moved on a two track road along a ridge.  This seems to have been reasonably safe at least at first as they had a view of the fire and various retreat options if it moved towards them.  However they then left the road (which would have eventually taken them to their apparent goal) to descend off the ridge through a box canyon directly towards their destination (a ranch with a cleared area).  Although this was a shorter route than continuing along the road it probably wasn't quicker as it was much heavier going.  The report speculates that the ranch appeared closer than it was and that they didn't realize how slow the going would be.  The real problem however was once they left the ridge they lost sight of the fire and (according to the report) the ability to perceive the wind shift that drove the fire towards them.  By the time they realized they were in danger it appears it was too late to do anything.  The report lists some of their options at the point they left the ridge but does not discuss one possibility.  Why didn't they leave a scout on the ridge to keep watch on the fire and warn them if it started to move towards them?  They had utilized a scout earlier in the day in what seems like a less dangerous situation so why not here?  The report doesn't discuss this.

The report doesn't want to admit that any mistakes were made.  This makes it hard to identify problems and make improvements going forward.  The report's view is that firefighting is inherently dangerous and that these 19 deaths were just one of those things.  I am not convinced.

Added 12/25/2013:  I fixed the link to the report.  Some other material including a video was also released.