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Comment Useful, but it doesn't solve the whole problem (Score 1) 96

Former builder here. The idea is great, but it seems fixated on the building shell, which is by far the cheapest part of the house. The electrical, plumbing, foundation, flooring, plaster, sidewalk, fencing, driveway and roofing work, the baths and kitchens, windows, doors, siding and trim are where all the money goes.

I do like the idea of being able to print out the complex stuff, say the framing for an archway or stairway. Otherwise, no way 3D printing can compete with pre-cut 2x4s.


Yawn. Let me know when it's out of the lab.

Comment Discrete vs. continuous math (Score 2) 656

When I was in grad school, I noticed that the EE classes were all about continuous math. EE deals with a mostly analog world and you need all those partial differential equations to work in it.

On the other hand, the CS classes were all about discrete math. The EE guys give us machines that provide an environment based on binary math and logic. You need to understand finite automata, compilers, data structures, algorithms, and so on to work in that world.

Myself, I found that I liked discrete math better, but that's me.

One piece of advice. Learn and understand networking. You'll never be sorry.


Theory blazes the trail, but it can't pave the road.

Comment Beware PUE lies (Score 1) 198

As a one-time member of The Green Grid Technical Committee, let me summarize and correct a few points:

  • The EPA has said that data centers use around 4% of US power. The federal government uses going on half of that, IIRC.
  • Historically PUEs of 2.4 were common. It makes sense. In a closed building, it takes 1 unit of cooling energy to cool the heat produced by one unit of computation etc. The cooling systems were say 80% efficient so that makes 1.25 units of cooling energy. Add in power conditioning and UPS losses, and you easily get 1.4 to 1.6 units of non-computational work for every unit of computation, for a PUE of 2.4 to 2.6.
  • A PUE of less than 1.0 is by definition impossible. Nevertheless, a few deluded individuals have reported them.
  • In anything less than ideal conditions, getting the PUE below 1.2 is very difficult. A common mistake is to allow equipment fans to do some of the work of the heat exhaust fans. This effectively transfers facility load to the equipment and results in artificially low numbers.
  • Low PUEs are harder to achieve in high-resiliency conditions. The large server farms used by MS and Google do not require the level of availability that enterprise data centers commonly do. These companies have the luxury of trading off equipment failure rates with power costs.
  • Uninformed data center managers sometimes think they can use unconditioned outdoor air as a coolant. This is ill advised. High humidity levels, high sulfur and other contaminant levels, and particulates can cause premature equipment failure, not to mention voiding warranties. I visited a data center in a hot and humid location once that had had 40% disk drive failure in a year. It's best to consult a professional data center HVAC specialist with experience in low-PUE installations.
  • Power costs do sometimes exceed CAPEX over the life of the equipment. It depends on location and up-front equipment cost.
  • Power gotten from public hydro is not "green". Power in the public grid is a zero-sum game. Only renewable energy that you produce yourself is more green than the average greenness of the public utility system.
  • The data centers located near big dams don't get cheap power because they're being green. They get it cheap because they avoid grid distribution costs. The same thing can be accomplished by colocation with a big coal plant. It just doesn't sound as cool.

Comment Generating or just using? (Score 2) 262

Renewable power bought from a utility company is a zero-sum game--only one party gets to use it, and everyone else gets stuck with whatever's left. So until they are actually generating all that power themselves, the claim is just chest thumping. No real benefit to the environment.

Comment Re:Those are our oldest ancestors? (Score 1) 85

I had a similar thought. Granted that we share the same molecular machinery, but it seems to me that we probably evolved from the hosts the bacteria fed on, not from the bacteria themselves. Unless they ate rock, in which case we evolved from the hosts their mutations ("descendants") fed on. For me, the jump from asexual to sexual reproduction is the really interesting inflection point. Do we really believe that an ordinary mutation caused that? (IANAE).

Comment Lecturing is not teaching (Score 1) 102

A couple of my academic friends believe that MOOCs like Khan Academy will "invert" the teaching process. Instead of attending lecturers for content, and assimilating the material later while doing homework, students will view lectures offline, and assimilate the material in class, in a more lab-like environment.

Sounds good to me.

Comment Re:Here here! Well said. (Score 1) 795

I appear to be the only ./er who cares enough to mention that it should be "hear, hear", not "here here".

That said, I agree with the sentiment, if not the spelling. My former employer, who shall go unnamed, is a dynamic Silicon Valley hi-tech company, once one of the best places in America (pre-Google) for bright geeks to work. It is now a sea of H1Bs. A small percentage of them are stars; the rest are merely inexpensive. And the worst part is that H1B managers rarely hire Americans; they prefer to manage other H1Bs.

Submission + - Mathematical constants considered harmful (in some contexts) (

drdrgivemethenews writes: "In a story about the laziness and lack of imagination most users bring to the task of choosing passwords, the researcher points out that 'dictionary' attacks using a short list of often-used passwords will have nice hit rates (in the 20% range). He goes on to note that 'The 17th most common 10-digit password is 3141592654'. Pretty funny to see math nerds hoisted on the petard of their own cleverness."

Comment CFLs are unbelievable (Score 3, Interesting) 1080

Unbelievably bad, that is. The light is poor and barren. I have yet to see a "100w equivalent" that was even close to being as bright as a 100w incandescent. Some of them have a power factor of 0.5, which means they're actually half as "energy efficient" as the label says. And "long-lasting"? Not in my experience. But hey, at least they're expensive.

The lighting industry has got to be gleefully rubbing its hands over these regulatory moves.

The building inspector made me replace 160 watts of very nice halogens in my new kitchen with 160 watts of fluorescents because the code says half of the lighting in a kitchen has to be "energy efficient". The overall lighting level went down considerably with this change, in part because the halogens give directed light and decent looking fluorescents don't, and also because halogen light is a lot nicer. Of course the change was reversed the same day the inspector signed off. The $120 fluorescent fixture I was forced to buy now illuminates an area of my home that I don't spend much time in--the laundry room.

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Stinginess with privileges is kindness in disguise. -- Guide to VAX/VMS Security, Sep. 1984