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Laser Eye Surgery, Revisited 10 Years Later

pthisis Re:My reason (550 comments)

Age related myopia is a fact of life. It affects your reading ability and pretty much everyone gets it.

You're completely wrong here:
1. Myopia affects your ability to see at a distance, it does not affect your reading ability. Most people do not get it; it typically develops until age 20-25 in those who do get it. It's the reason for most glasses and contacts in people under age 40. LASIK is most commonly used as a correction for those with myopia.
2. Presbyopia is the age-related age decline that most people get; it affects your ability to focus, which is why many old people need reading glasses or bifocals. It tends to start sometime after age 40 and progress.
3. People with myopia absolutely tend to have much-delayed onset of significant presbyopia, less severe cases, and sometimes avoid it entirely; LASIK eliminates those delays.

See, e.g., the American Optometric Association's Care of the Patient with Presbyopia:
http://www.aoa.org/documents/o...
Patients with uncorrected or undercorrected myopia are less likely to experience difficulty with near tasks... Due to lens effectivity, patients who wear spectacle
corrections for myopia experience presbyopia later than those with emmetropia or hyperopia. Patients with myopia typically require less powerful bifocal additions than same-age patients who wear spectacle corrections for hyperopia.

You don't eveb need to deep-dive into the AOA to find this out, either; even Wikipedia says "Many people with myopia (near-sightedness) can read comfortably without eyeglasses or contact lenses even after age 40. However, their myopia does not disappear and the long-distance visual challenges remain. Myopes considering refractive surgery are advised that surgically correcting their nearsightedness may be a disadvantage after age 40, when the eyes become presbyopic and lose their ability to accommodate or change focus, because they will then need to use glasses for reading. Myopes with astigmatism find near vision better, though not perfect, without glasses or contact lenses when presbyopia sets in, but the more astigmatism, the poorer their uncorrected near vision". http://en.wikipedia.org/wiki/P...

about a month ago
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Laser Eye Surgery, Revisited 10 Years Later

pthisis Re:My reason (550 comments)

Thats' not my understanding at all. my understanding is that when you get old your vision doesn't so much "change" as become less "elastic", you loose the ability to easily re-focus.

That much is true, but myopic individuals are naturally focused at nearer range. It's not uncommon for presybobia--or at least significant enough to need reading glasses--to be delayed past age 50 in people with myopia (especially those with little or no astigmatism), or even avoided altogether. Well, that's not entirely correct: if you're wearing your contacts or glasses, you'll need to take them off to see at close range during that interim period.

http://www.aoa.org/documents/o...

"Due to lens effectivity, patients who wear spectacle corrections for myopia experience presbyopia later than those with emmetropia or hyperopia. Patients with myopia typically require less powerful bifocal additions than same-age patients who wear spectacle corrections for hyperopia."

about a month ago
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Laser Eye Surgery, Revisited 10 Years Later

pthisis Re:My reason (550 comments)

That's what you'll have to do if you have LASIK. If you don't have LASIK, you'll avoid the need for reading glasses or push it back by many years. That's kind of the point.

about a month ago
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Laser Eye Surgery, Revisited 10 Years Later

pthisis Re:My reason (550 comments)

Yep. My dad's an ophthalmologist, and he doesn't recommend LASIK for anyone over 30 because of this (except in a handful of unusual circumstances). You're trading off future reading vision for distance vision now, and the older you get the closer "now" becomes.

I'll gladly keep my ability to read without holding things at arm's length or putting on reading glasses for as long as possible, though admittedly my distance vision isn't that bad (I wear my contacts if I'm going to a movie or something, but I don't need to wear them for normal daily life) and I was already pushing 30 by the time LASIK really matured (about 10 years ago)

If you're, say, 26 now (so you'll get a good 14-20 years of fully corrected vision) and have terrible distance vision, LASIK may make a lot more sense.

about a month ago
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X.Org Server 1.16 Brings XWayland, GLAMOR, Systemd Integration

pthisis Re:Systemd? Not on my system... (226 comments)

No, generally emacs users are happy with systems that have both emacs and vi, and emacs won't prevent vi (and all the tools depending on ex/ed) from working.

Except when distributions screw up their dependencies, which they almost all did for about the first 10 years.

Emacs' crappy legacy ctags was part of the emacs package rather than a separate ctags package (despite the fact that emacs itself prefers etags). Hence it was impossible to install emacs and have modern functional code navigation in vi (vim/elvis/nvi) without overriding the rpm/dpkg dependencies or some other hack.

(This is not emacs' fault, it's the distributors who screwed it up for years).

about a month ago
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The Video Game That Maps the Galaxy

pthisis Re:Of course (28 comments)

Gravity was modelled and absolutely key in Starflight--if you tried to land on planets that were too high-grav, your lander would crash and you'd die. So scanning for gravity was among the more important aspects of a landing mission.

about a month ago
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The Video Game That Maps the Galaxy

pthisis Of course (28 comments)

Braben boasts that his games predicted extra-solar planets ('These were pretty close to those that have been since discovered, demonstrating that there is some validity in our algorithms'), and that the game's use of current planet-formation theories has shown the sheer number of different systems that can exist according to the rules, everything from nebulous gas giants to theoretically habitable worlds.

Starflight did this in 1986.

about a month and a half ago
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Washington Redskins Stripped of Trademarks

pthisis Re:Free Speech (646 comments)

This is not a free speech issue. You are allowed to say and write "redskin" anywhere you wish. You just can't trademark it.

Yes, you can. This decision explicitly doesn't revoke the team's right to use the trademark "Redskins". It removes it from the USPTO primary registry, but it doesn't revoke the trademark (in other words, what was an (R) is now a (TM)).

about 2 months ago
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Washington Redskins Stripped of Trademarks

pthisis Re:My two cents (646 comments)

They had a trademark on their brand. The feds decide they don't like the mark so they take it away. The owners end up being harmed economically all because the government didn't like the descriptive nature of the brand. They've effectively stifled the free speech of the owner by denying them the use of the mark.

Please read the decision. They have done no such thing, and haven't cancelled the trademark. They've removed it from the primary registry. The team still has full protected (TM) rights, and third parties won't be allowed to make knockoff jersey with the name on it or anything like that. It's just not a registered (R) trademark anymore.

From the decision:
This decision concerns only the statutory right to registration under Section 2(a). We lack statutory authority to issue rulings concerning the right to use trademarks. See, e.g., In re Franklin Press, Inc., 597 F.2d 270, 201 USPQ 662, 664 (CCPA 1979).

about 2 months ago
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Washington Redskins Stripped of Trademarks

pthisis Re:My two cents (646 comments)

The trademark exists to protect their business interest in the brand name. The feds aren't canceling the mark because other business entities want to use it, they're canceling the mark because the feds don't like it.

This is wrong. The feds aren't canceling the trademark, period. They are canceling its presence on the USPTO primary registry (where it's not allowed to be under the Lanham act), but it'll still be a (TM) trademark with court protection (just not an (R) registered trademark).

From the decision itself:

This decision concerns only the statutory right to registration under Section 2(a). We lack statutory authority to issue rulings concerning the right to use trademarks. See, e.g., In re Franklin Press, Inc., 597 F.2d 270, 201 USPQ 662, 664 (CCPA 1979).

about 2 months ago
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Washington Redskins Stripped of Trademarks

pthisis Re:My two cents (646 comments)

The government is not restricting speech at all. The summary is hopelessly dumb: the decision doesn't strip the team of their trademarks, it simply removes them from the USPTO registry as required by the Lanham act. They'll still be protected (TM) trademarks that nobody except the owner is allowed to use, they just aren't (R) registered (which has implications on venue and damages).

From the decision itself:

This decision concerns only the statutory right to registration under Section 2(a). We lack statutory authority to issue rulings concerning the right to use trademarks. See, e.g., In re Franklin Press, Inc., 597 F.2d 270, 201 USPQ 662, 664 (CCPA 1979).

about 2 months ago
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Washington Redskins Stripped of Trademarks

pthisis Re:Chicago Blackhawks too? (646 comments)

Redskins isn't being stripped of their trademark, the summary is completely wrong.  They're just not being allowed on the primary registry.  They'll still have (TM) protection, but not (R) protection.

NWA never attempted to register, AFAIK.

about 2 months ago
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Ask Slashdot: Best Rapid Development Language To Learn Today?

pthisis Re:Type of applications (466 comments)

awk is fine for one-liners and for simple takes on moderately large files can be 5-6x faster than Perl.  For all that perl has the reputation for being a grep/sed/awk replacement, it's incredibly slow at the job.  Sometimes that matters.

For anything larger than a one-off, I'd go with python/pypy (ruby and lua are also fine choices).

$ time awk '{print $1}' < f4.txt >/dev/null

real    0m0.296s
user    0m0.288s
sys    0m0.004s

$ time perl -pale '$_="@F[0]"' < f4.txt >/dev/null

real    0m1.920s
user    0m1.896s
sys    0m0.020s

$ time python -c "import sys;[sys.stdout.write(line.split()[0]+'\n') for line in sys.stdin]" < f4.txt >/dev/null

real    0m0.618s
user    0m0.604s
sys    0m0.008s

$ time pypy -c "import sys;[sys.stdout.write(line.split()[0]+'\n') for line in sys.stdin]" < f4.txt >/dev/null

real    0m0.531s
user    0m0.508s
sys    0m0.020s

about 2 months ago
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Ask Slashdot: Best Rapid Development Language To Learn Today?

pthisis Re:Converting to "simple strings" itself takes tim (466 comments)

If you have a CPU-intensive thing, you can use shared memory and binary structs to share it, no need to turn everything into a string.

about 2 months ago
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C++ and the STL 12 Years Later: What Do You Think Now?

pthisis Re:Feels Dated (435 comments)

I think that Slashdot ate some of your formatting (angle brackets?). I'm not sure how the hash table is used for messaging (you might want to consider Unix domain sockets for messaging, depending on what's going on). But...

You can basically grow shared memory segments on the fly. They're shared in the FS page cache, so if you create a "new" memory mapping on the same backing file that's just bigger, it'll contain all the same stuff in the original segment as the original mapping.

So you just:

a = mmap(..., 2 megabytes,...)

(Use for a while, realize that it's too small)

old = a
new = mmap(..., 4 megabytes, ...)
a = new
munmap(old)

You have to do that per-process, but you can either have the initial part of the memory indicate the mapping length (every time you use it, check the length and reallocate if you're off) or you can use a semaphore or socket message or other OOB message to indicate when to resize.

I don't see how this is (theoretically) any harder in C++ than in Java as far as the problem specifics go (I mean ignoring general reasons that C++ is harder than Java).

Also when they say that a python Manager object is slow, access to it should be considered similar to access to a synchronized method in Java. But reading large amounts of data over it can be problematic, depending on exactly how you're using it.

Depending on your access needs and where your bottlenecks are, I'd also consider using memcached or something like that if you think you might ever expand to multiple machines.

about 3 months ago
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C++ and the STL 12 Years Later: What Do You Think Now?

pthisis Re:Feels Dated (435 comments)

Go doesn't have support for fork without exec, or at least didn't last time I looked at it.

I need async execution of things with read access to lots of data, and write access to their own data.

This sounds like shared memory segments to me. You can enforce memory protection by having separate mappings per process that are only writeable by the owner, with the processes running as separate users. That's safest but requires separate users and can be a headache for some tasks. Alternatively you could rely on the open/map calls being right and use read-only mode there but run as one user (you'd still protect against random pointer bugs, mistakes about which data structures you're writing into, etc as long as the open calls were correct).

ALL I need is synchronization

What kind of synchronization? What are your performance requirements? You may want want to consider simple mutexes, spinlocks, token passing, or read-copy-update depending on what you're doing.

about 3 months ago
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C++ and the STL 12 Years Later: What Do You Think Now?

pthisis Re:Feels Dated (435 comments)

BTW the basic architecture choices are similar across most languages; whether it's C or Python or Lisp or C++ or whatever, you're looking at a handful of common primitives for synchronization and data sharing, often with thin language-specific wrappers around them.

The most common times that there's a major difference is when either in a highly functional language designed around concurrency (e.g. erlang) or a language that isolates you so much from the environment that you can't easily use common primitives (Java's inability to get to multiprocess calls is the most obvious example).

about 3 months ago
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C++ and the STL 12 Years Later: What Do You Think Now?

pthisis Re:Feels Dated (435 comments)

I'd need to know more about your app to make a real recommendation, but in general for multiprocessing I'd use fork without exec to spawn new processes; they will share memory in a copy-on-write manner, so the python interpreter itself and other read/execute only memory will be shared between all processes.

There are numerous approaches to data sharing--sockets/pipes for streaming data and memory-maps for shared memory segments (memory maps are generally preferrable to SysV shm segments, IMO), and either token passing via pipes or something like multiprocessing.Lock for synchronization.

Your cells may want an event-driven state machine model. It's tough to say without knowing more about the app.

about 3 months ago
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C++ and the STL 12 Years Later: What Do You Think Now?

pthisis Re:Feels Dated (435 comments)

But Python doesn't handle multi-processing well

Python's great for multi-processing, much better than Java (which has no built-in solution for multiple processes/tasks, requiring you to throw out the benefits of protected memory or resort to hacky multiple JVM solutions with home-brewed synchronization primitives in order to take advantage of multiple CPUs).

Java's better for multi-threading, but that's usually a poor approach to multi-processing and in the real world the GIL problems with Python are often (but not always) overstated--e.g. the GIL is released by C extensions, so if you're using numpy or PIL or something then it's a non-issue much of the time. And Python has excellent support for fork-without-exec, shared memory maps, and other things that are important to good multiprocessing.

about 4 months ago

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