Shallow Thoughts : : Nov
Akkana's Musings on Open Source Computing and Technology, Science, and Nature.
Wed, 27 Nov 2013
A recent episode of the Freakonomics podcast
What Do Skating Rinks, Ultimate Frisbee, and the World Have in Common?,
talked, among other things, about Sportsmanship in Ultimate Frisbee
versus other sports.
Ultimate Frisbee is self-policing. It has no referee:
if someone on the field thinks they've been fouled, they call it out,
and the two players reach a consensus.
Why don't the players cheat and take advantage of the lax rules and the
lack of a referee? Because sportsmanship and honesty is part of the
culture of the game, in a way that isn't true in refereed sports like
soccer, basketball, tennis or nearly any other sport played professionally.
The Ultimate players they interview talk about
the culture of the game, the longtime attitude that every player is
"morally bound to abide by the rules. The integrity of Ultimate
depends on each player’s responsibility to uphold the spirit of the
game."
And that's great. But I submit that there's a more important reason:
because there's not much at stake in Ultimate Frisbee, compared to
football, soccer or basketball.
Ultimate is still a chiefly hobby sport which is only
barely starting to get sponsorships and professional teams.
I'm not up on the Ultimate scene, but I bet there aren't a lot
of millionaire players yet, or a lot of poor kids practicing their
frisbee throws as their way out of the ghetto.
To make my point, let me tell you a tale of two autocross classes.
Autocross, if you're not familiar with it, is miniature car racing.
You race against the clock, one car at a time, on a course delimited
by traffic cones on a large parking lot or airstrip.
There are lots of different classes, so cars race against similar
types of cars. The classes cover different preparation levels,
starting with Stock classes, where you can't make any modifications
beyond tires, shocks and a few other carefully specified items.
Next above stock is Street Prepared, where the cars are still
more or less street legal (many are still daily drivers),
but they have lower, stiffer suspensions, wider wheels, sometimes
headers or high-flow mufflers or fancy intake systems.
Then above that are Race Prepared, for cars prepped to road racing
standards, and Modified, for purpose-built race cars like formula cars.
Autocross, when I was actively racing (and I doubt it's very
different now), is almost entirely an amateur sport. There are
some sponsorship programs, called "contingency programs", where
you can earn a few hundred dollars if you win a big race using
the right car, the right tires, the right shock absorbers.
Some races throw in modest amounts of prize money, so that at a
big national level event a handful of winners might be taking home a few
thousand dollars over their travel expenses, maybe ten thousand
at the absolute top end. Most class winners don't even make enough to
pay their travel expenses.
Curiously, the best contingency money isn't in the superfast, exciting
Modified classes; it's in Stock. Why?
Because the money comes from manufacturers hoping that
someone will see your stock Miata winning the class and say "Wow, maybe
I should buy a Miata too!" or "Maybe what my Miata needs is those
tires/shocks/whatever."
I ran my Fiat X1/9 in D Street Prepared.
DSP is seen as a class for old clunkers --
some of the winning cars besides the X1/9 included the Mazda RX3,
VW Rabbit, Datsun 510,
Datsun Roaster, and CRX HF. They're all old cars, no longer on
the market -- so manufacturers weren't very interested in offering
contingency money for them. That was okay -- our cars were fast and
fun to drive, we had great competition and a lot of fun.
Everybody was friendly with each other -- sure, we were all out to win,
but if someone had car trouble, you could bet that everyone would
be gathered around the car trying to help. If the problem wasn't fixable,
another competitor would offer a ride in another DSP car. I saw that
happen even at Nationals -- everybody was intensely competitive, but in a
friendly way.
That's not to say nobody ever cheats. Sure, occasionally somebody
wanted to win badly enough that they'd make some illegal modification
to their car. Sometimes they even got away with it for a year or two
before anyone figured it out. But cheating was relatively rare ... at
least until contingency money started to edge up into the thousands of
dollars instead of just a few hundred. Then you started to see a lot more
protests, a lot more engines and suspensions turn down, and a lot more
cars found illegal and disqualified.
And most of the protests happened in the stock classes.
And then one year at Nationals, I really learned how those big
contingency prizes changed the sport. I was running my old Fiat in DSP
as usual (actually DSPL, the parallel class for women drivers).
A friend of mine was there in a stock car she'd bought just the year
before. She'd worked really hard all year, was driving exceptionally
well and was widely thought to have a good chance to win her class.
(I'm deliberately omitting her details like name, make and class.)
We were all rooting for her.
And then one morning, a day or so before her class was scheduled to run,
she discovered that one of her brake lines had been cut.
Her brake line!
On her daily driver car that she was going to drive 1,500 miles home
after Nationals was over!
Fortunately, she found it in time, and lots of people pitched in to
help her get the brake line fixed. But it was pretty terrifying to
know that something like that was even possible in what I had always
seen as a friendly, fun, amateur sport.
I don't know if anything else like that happened in other classes.
It wasn't widely talked about; you might not have known about it happened
if you didn't know someone involved. They never found out who did it,
as far as I know.
But there were a lot of protests in the stock classes that year, too
-- nobody trusted anyone, everybody assumed their competitors were
cheating, and there were engine and suspension teardowns.
It all made me glad I was in unassuming (and fun!) old DSP and out of the money.
So, getting back to the Ultimate referee question. Yes, sports that have a
friendly, sportsmanlike culture are terrific. But I think -- though I
wish I didn't -- that the Ultimate players may find, as their
professional league gets off the ground and they attract more
sponsors, that the moral code they've taken for granted is partly due
to not having much at stake.
Money, or the prospect of it, does something to people.
And I'm not sure money and stand-up honest sportsmanship make
very good bedfellows.
Tags: sport, competition, freakonomics, autocross
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17:16 Nov 27, 2013
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Thu, 21 Nov 2013
I woke up thinking about dinosaurs.
Specifically, Pachycephalosaurus, the bone-headed dinosaur, and her
long-crested cousin
Parasaurolophus
(pictured at right).
The previous night, I had been reading
The Know-It-All,
A. J. Jacob's entertaining account of his adventures reading the whole
Encyclopedia Britannica. I'd left off in the Ps, which included a very
short entry on Pachycephalosaurus (A.J. is not particularly into
dinosaurs).
Drifting along in a typical insomniac "I wish I could get back to sleep"
haze, I couldn't help noticing that Parasaurolophus was six syllables --
in fact, it was a double dactyl.
And that meant it was a prime candidate for my favorite verse form,
double-dactylic
doggerel, a form with fairly strict rules which require, among
other things, that the second line be a double-dactylic proper name.
And as double-dactylic junkies know, once you've noticed a
double-dactylic name, you can't rest until it's turned into a poem.
So now I couldn't sleep because I was thinking about Parasaurolophus.
Now, even aside from its mellifluous name, Parasaurolophus and the whole
Hadrosaur family
are pretty interesting. The biggest puzzle is why they had those
elaborate bony crests.
Decoration for mating purposes? Fighting, like horns and antlers
on modern hoofed mammals? But in the late 1990s, CT scans of hadrosaur
fossils revealed long air passages inside the crests of many
Hadrosaurs, including Parasaurolophus ... and those air passages were
connected to the nasal passages.
That led to suggestions that the crests might have been tuned for
sound production -- a built-in wind instrument.
In Scientists Use
Digital Paleontology to Produce Voice of Parasaurolophus Dinosaur
a team at Sandia made computer models of the air passages,
and you can even listen to sound files of what Parasaurolophus might have
sounded like. The sound is wonderful, like a trombone. Sandia's
pages use a, <embed> tag that didn't work for me in Firefox, so
if you have trouble with their links, I've separated out the
wav file URLs:
songLQ.wav (588k)
and a higher quality version,
song2.wav (2.7M).
Anyway, I never did get back to sleep, but I did end up with some
insomniacal doggerel:
Dinosaur, schminosaur
Parasaurolophus
How do you use that
Magnificent crest?
"I play trombone in the
Dinosaur orchestra
All hadrosaurs play, but
I am the best."
Tags: dinosaur, poetry, writing
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16:49 Nov 21, 2013
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Sun, 17 Nov 2013
I signed up yesterday for a health care plan on California's health
insurance exchange, CoveredCA.
It wasn't pretty, but I signed up for a plan in the end. Or at least,
I think I did.
The process was full of hilarity, a several hour haul involving
pages that didn't work, pages with mistakes on them, and of course,
timeouts and restarts.
Brief thought before I begin: California's healthcare site is
CoveredCA.com. That's dot com.
I keep seeing articles in the newspaper warning people not to get
confused by imitator sites, as there are several with names similar
to the official site
(Update: see, for example,
Kamala
Harris shutters 10 fake Covered California websites
and
State
shuts down bogus health care websites)
, and I always wonder -- why don't government
sites take advantage of dot gov domains? You see the same thing on the
national credit-report-check website: there's a dot com website where you
can get your official government-sanctioned free credit report, and then
there are about twenty imitator sites with names that any normal person
would confuse with the real site, which are basically scams that try
to suck you in to paying for various products in the guise of giving
you your free credit report.
Government folks: the whole point of dot gov is to tell us it's a
government-sanctioned site. Please use it.
Anyway, back to CoveredCA.com.
I had already been on the site a few days earlier. CoveredCA says that
you can browse plans without signing up for an account. That's sort of
true -- but that's not really true. You can browse plans, sure ... but
you can't find out any useful information about sorts of subsidies you
might qualify for. The site asks you questions
about your location, your income and the age of everyone in your household,
then deposits you on a page that chirpily informs you "You may be
eligible for ..." a list of every possible type of plan, from Medi-cal
(California's version of Medicaid) to regular exchange plans to ...
aid to mothers and infants? When I've already filled out a form saying
that there are no children in the house?
At the bottom right is some small print
saying that you have to create an account to find out what
you're actually eligible for. Then why ask those other questions?
Okay, so I guess I need to sign up even to browse. With trepidation
I began the sign-up process.
Signing up
The first hurdle came only a few screens in, when I typed in my address.
123 Mystreet Ave, San Jose, CA, 91234. I got an error screen.
Confirm Your Mailing Address
The address you've entered is different from those on file. Please
confirm which is correct.
The address you entered
|
• | 123 Mystreet Ave,
|
| San Jose,
|
| CA,
|
| 98765
|
Possible Address 1
|
| 123 Mystreet,
|
| Ave,
|
| San Jose,
|
| CA,
|
| 98765
|
See the difference? It took me a minute, but they have a comma between
my street name and "Ave".
I don't normally put a comma there, and I don't think most people do.
So I left "The address you entered" checked. I probably shouldn't have:
later in the process, it asked me my address again (don't they have, like,
you know, a database, so people don't have to enter the same address
multiple times?) and it showed me the exact same screen.
I stubbornly stuck to my guns and continued to insist on the version
without the spurious comma, whereupon the site stopped responding at
all, and fifteen minutes went by without any pages loading. I tried
reloading, going back, etc. but I finally had to give up and reload
CoveredCA.com. Fortunately, it had saved at least some of my work so I
didn't have to start from the beginning.
Accepting the commaed version might not have helped, anyway.
These 10 or 15 minute delays were fairly common throughout the process.
Two or three times, while I was waiting for a page to load, I got an amusing
(I just accidentally typed that as "abusing" -- talk about a Freudian slip!)
popup saying that my session was about to time out, did I want to continue?
Garbled pages
The next snag (aside from timeouts) I hit was the Household Authorized
Representative Information page. I was out of the room when it loaded,
since it took many minutes to get from the previous page to that one,
so I didn't see it load, but when it did, this is what I got:
(click on the image for the full screenshot).
Um? Did we time out and only load a partial page?
I crossed my fingers and hit the browser's Reload button.
I watched a page full of questions come in -- whew! Except that about
a second after the page finished filling with questions, they all
vanished, to be replaced by the same thing I'd seen before.
I'm not entirely sure what this screen is for. Of course I would want
my husband authorized. But I can always give him the password I used
to log in, and I'm not sure he isn't automatically authorized anyway.
Maybe this screen is for authorizing someone else. Anyway, let's just
hope the default is okay and I'm not agreeing to anything I don't want,
and click Continue.
And the end of the process was a statement to
read and sign, under penalty of perjury. It included this
amusing paragraph:
I know that I must tell the (Co-Brand Application Name) if anything
changes from (and is different than) what I have provided on this
application.
I'll be sure to notify (Co-Brand Application Name). I promise.
Meanwhile, do you have anything to tell me about Lorem ipsum?
Choosing a plan
I finally got through the signup process, about two hours after I started.
Whew! It said I could now choose a plan. But when I clicked on that button,
no page loaded. I waited 15 minutes, gave up and clicked Reload, waited
another 15 minutes, and then had to leave for a meeting. So I clicked
Stop, hoping that the site had saved all my info and I'd be able to
look at plans later that afternoon.
When I returned to the computer, of course my attempt to click on the
button to choose a plan took me to a Server Error page. I expected that,
after letting the computer sleep for several hours. So I loaded CoveredCa
and logged in again.
This time I was able to get into the "Find a Plan" part of the site.
(Less traffic in the afternoon? Or was the button from the signup page
taking me to the wrong place? I'll probably never know.)
The user interface on the plan comparison page is horrifying. You're
shown three plans at once (no, resizing the browser window doesn't increase
that number). Then there are two nested scrollbars: the outer one scrolls
the page that includes the names of the three plans, while the inner one
only scrolls the part you can see below the big rectangle describing each
plan. Assuming there is anything you can see below that part: I had to
maximize my browser window to my 1680x1050 monitor and scroll the outer
page to where I could just barely see the names of the plans, and then
I still could only see a tiny fraction of the available details at
once. To really compare plans, you have to expand all the categories,
then scroll up, down, up, down, up, down, taking notes on paper since you
can't see more than half a category at once (and of course, only for the
three plans you're currently viewing).
Don't even bother trying this on a laptop.
If you want to see more than the first three plans, there are the amusing
scroll tabs.
On the left of the three plans is a tab with a symbol that looks like an equal
with dots above and below it: that scrolls left (if not already at the
first plan). On the right is a tab with the symbol alpha; that scrolls
right. Why those symbols? I have no idea. Maybe the UTF-8 codes
correspond to right-arrow and left-arrow in some Windows-based
design tool.
It took me quite a while to figure out how to tell which plans cover
which doctors. It's under the Summary category, My doctors,
Search.
Eventually I gave up on trying to compare plans intelligently, and just
picked the silver plan from our current provider which I was pretty sure
would cover our current doctors. Amazingly, it let me sign up, and told
me we were enrolled -- though it wouldn't be official until the provider
had contacted us about billing and we'd made the first payment. It said
we should expect them to contact us by November 15. (Checks calendar) ...
Why ... that's tomorrow! And it was about 2:30pm already.
That seems awfully quick. It's the 17th as I'm writing this ...
maybe there'll be something in tomorrow's mail.
And in case you're counting, the deal we'll be getting through the
ACA is stupefyingly better than the individual plan we were paying for
before. Like $10,000 a year better, with a $500 deductible instead of
the $4000/person deductible we had before. So don't get the wrong idea
from this snarky blog post -- I'm a big fan of health care reform.
It's just badly done websites I object to.
Survey: How are we doing?
Finally done! Wahoo! And at the end, there was a chance to fill in a
little survey about my experience on CoveredCA. Of course, I wanted to
tell them about the problems I'd encountered, so I clicked the button.
I filled out the survey and clicked Submit.
You know how if a form on https directs you to a non-SSL page, Firefox
gives you a warning about it? I got that warning here. But it didn't
concern me -- I'm not worried about whether my survey results are encrypted
when I'm sending them. So I clicked Continue.
And got this: you must use ssl to access this resource.
I about died laughing. A fitting end to hours of hilarity.
So as you read coverage of the problems with the national healthcare
exchange, and all the chirpy reports about how the states with their
own exchanges, especially California, are doing so much better, keep
this in mind. Especially when the articles mention things like not
having gotten much negative feedback or heard about problems their
users are having.
(Is this a good time to mention the helpful "Online chat" link at the
top of the CoveredCA site that just reloads the main page?)
You have to admit, a survey page that doesn't work is a great way to
reduce the amount of negative feedback you get!
Update: it's half a week later now; no word from the insurer. I went
back to CoveredCA and logged on to verify that I'm really enrolled.
On the main screen, it shows me a timeline with six steps:
Summary - Household - Personal Data - Income - Eligibility - Enrollment.
The first four have blue squares with checkmarks in them; Eligibility
has a blue square but no checkmark, and Enrollment is white and
un-checked. I have no idea what this means, but it doesn't look good.
The squares with checks are clickable; the others aren't.
Clicking around in desperation, I discovered by accident that if I
clicked on "Income" (the last clickable step), on the Income page it
added a checkmark under "Eligibility" in the timeline at the top,
making it clickable. If I then clicked on Eligibility, it didn't add
a checkmark for Enrollment, but it did give me a "Choose a plan"
button at the bottom, so I clicked on that. That took me to a
page titled "Household Enrollment Summary" which showed me the
plan I'd signed up for. There's a link over the "Carrier Website
Address" but it goes to a nonexistent page on v.calheers.ca.gov.
Meanwhile, in the top timeline, Enrollment is blue though it still
isn't checked.
So am I really enrolled in a plan? Wish I knew.
Tags: ACA, obamacare, health care, coveredca
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18:25 Nov 17, 2013
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Wed, 13 Nov 2013
Last week I wrote about some tests I'd made to answer the question
Does
scrolling output make a program slower?
My test showed that when running a program that generates lots of output,
like an rsync -av, the rsync process will slow way down as it waits for
all that output to scroll across whatever terminal client you're using.
Hiding the terminal helps a lot if it's an xterm or a Linux console,
but doesn't help much with gnome-terminal.
A couple of people asked in the comments about the actual source of
the slowdown. Is the original process -- the rsync, or my test script,
that's actually producing all that output -- actually blocking waiting
for the terminal? Or is it just that the CPU is so busy doing all that
font rendering that it has no time to devote to the original program,
and that's why it's so much slower?
I found pingu on IRC (thanks to JanC) and the group had a very
interesting discussion, during which I ran a series of additional tests.
In the end, I'm convinced that CPU allocation to the original process
is not the issue, and that output is indeed blocked waiting for the
terminal to display the output. Here's why.
First, I installed a couple of performance meters and looked at the
CPU load while rendering. With conky, CPU use went up equally (about
35-40%) on both CPU cores while the test was running. But that didn't
tell me anything about which processes were getting all that CPU.
htop was more useful. It showed X first among CPU users, xterm second,
and my test script third. However, the test script never got more than
10% of the total CPU during the test; X and xterm took up nearly all
the remaining CPU.
Even with the xterm hidden, X and xterm were the top two CPU users.
But this time the script, at number 3, got around 30% of the CPU
rather than 10%. That still doesn't seem like it could account for the
huge difference in speed (the test ran about 7 times faster with xterm
hidden); but it's interesting to know that even a hidden xterm will
take up that much CPU.
It was also suggested that I try running it to /dev/null,
something I definitely should have thought to try before.
The test took .55 seconds with its output redirected to /dev/null,
and .57 seconds redirected to a file on disk (of course, the kernel
would have been buffering, so there was no disk wait involved).
For comparison, the test had taken 56 seconds with xterm visible
and scrolling, and 8 seconds with xterm hidden.
I also spent a lot of time experimenting with sleeping for various
amounts of time between printed lines.
With time.sleep(.0001) and xterm visible, the test took 104.71 seconds.
With xterm shaded and the same sleep, it took 98.36 seconds, only 6 seconds
faster. Redirected to /dev/null but with a .0001 sleep, it took 97.44 sec.
I think this argues for the blocking theory rather than the CPU-bound one:
the argument being that the sleep gives the program a chance
to wait for the output rather than blocking the whole time.
If you figure it's CPU bound, I'm not sure how you'd explain the result.
But a .0001 second sleep probably isn't very accurate anyway -- we
were all skeptical that Linux can manage sleep times that small.
So I made another set of tests, with a .001 second sleep every 10
lines of output. The results:
65.05 with xterm visible; 63.36 with xterm hidden; 57.12 to /dev/null.
That's with a total of 50 seconds of sleeping included
(my test prints 500000 lines).
So with all that CPU still going toward font rendering, the
visible-xterm case still only took 7 seconds longer than the /dev/null
case. I think this argues even more strongly that the original test,
without the sleep, is blocking, not CPU bound.
But then I realized what the ultimate test should be. What happens when
I run the test over an ssh connection, with xterm and X running on my
local machine but the actual script running on the remote machine?
The remote machine I used for the ssh tests was a little slower than the
machine I used to run the other tests, but that probably doesn't make
much difference to the results.
The results? 60.29 sec printing over ssh (LAN) to a visible xterm;
7.24 sec doing the same thing with xterm hidden. Fairly similar to
what I'd seen before when the test, xterm and X were all running on the
same machine.
Interestingly, the ssh process during the test took 7% of my CPU,
almost as much as the python script was getting before, just to
transfer all the output lines so xterm could display them.
So I'm convinced now that the performance bottleneck has nothing to do
with the process being CPU bound and having all its CPU sucked away by
rendering the output, and that the bottleneck is in the process being
blocked in writing its output while waiting for the terminal to catch up.
I'd be interested it hear further comments -- are there other
interpretations of the results besides mine?
I'm also happy to run further tests.
Tags: performance, linux, programming, python
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17:19 Nov 13, 2013
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Fri, 08 Nov 2013
While watching my rsync -av messages scroll by during a big backup,
I wondered, as I often have, whether that -v (verbose) flag was slowing
my backup down.
In other words: when you run a program that prints lots of output,
so there's so much output the terminal can't display it all in real-time
-- like an rsync -v on lots of small files --
does the program wait ("block") while the terminal catches up?
And if the program does block, can you speed up your backup by
hiding the terminal, either by switching to another desktop, or by
iconifying or shading the terminal window so it's not visible?
Is there any difference among the different ways of hiding the
terminal, like switching desktops, iconifying and shading?
Since I've never seen a discussion of that, I decided to test it myself.
I wrote a very simple Python program:
import time
start = time.time()
for i in xrange(500000):
print "Now we have printed", i, "relatively long lines to stdout."
print time.time() - start, "seconds to print", i, "lines."
I ran it under various combinations of visible and invisible terminal.
The results were striking.
These are rounded to the nearest tenth of a second, in most cases
the average of several runs:
Terminal type | Seconds
|
xterm, visible | 56.0
|
xterm, other desktop | 8.0
|
xterm, shaded | 8.5
|
xterm, iconified | 8.0
|
Linux framebuffer, visible | 179.1
|
Linux framebuffer, hidden | 3.7
|
gnome-terminal, visible | 56.9
|
gnome-terminal, other desktop | 56.7
|
gnome-terminal, iconified | 56.7
|
gnome-terminal, shaded | 43.8
|
Discussion:
First, the answer to the original question is clear. If I'm displaying
output in an xterm, then hiding it in any way will make a huge
difference in how long the program takes to complete.
On the other hand, if you use gnome-terminal instead of xterm,
hiding your terminal window won't make much difference.
Gnome-terminal is nearly as fast as xterm when it's displaying;
but it apparently lacks xterm's smarts about not doing
that work when it's hidden. If you use gnome-terminal,
you don't get much benefit out of hiding it.
I was surprised how slow the Linux console was (I'm using the framebuffer
in the Debian 3.2.0-4-686-pae on Intel graphics). But it's easy to see
where that time is going when you watch the output: in xterm, you see
lots of blank space as xterm skips drawing lines trying to keep up
with the program's output. The framebuffer doesn't do that:
it prints and scrolls every line, no matter how far behind it gets.
But equally interesting is how much faster the framebuffer is when
it's not visible. (I typed Ctrl-alt-F2, logged in, ran the program,
then typed Ctrl-alt-F7 to go back to X while the program ran.)
Obviously xterm is doing some background processing that the framebuffer
console doesn't need to do. The absolute time difference, less than four
seconds, is too small to worry about, but it's interesting anyway.
I would have liked to try it my test a base Linux console, with no framebuffer,
but figuring out how to get a distro kernel out of framebuffer mode was
a bigger project than I wanted to tackle that afternoon.
I should mention that I wasn't super-scientific about these tests.
I avoided doing any heavy work on the machine while the tests were running,
but I was still doing light editing (like this article), reading mail and
running xchat. The times for multiple runs were quite consistent, so I
don't think my light system activity affected the results much.
So there you have it. If you're running an output-intensive program
like rsync -av and you care how fast it runs, use either xterm or the
console, and leave it hidden most of the time.
Tags: performance, linux, programming, python
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15:17 Nov 08, 2013
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Sun, 03 Nov 2013
While practicing a talk the other night on my new Asus laptop, my
Logitech remote presenter,
which had worked fine a few hours earlier, suddenly became flaky.
When I clicked the "next slide" button, sometimes there would be a
delay of up to ten seconds; sometimes it never worked at all, and I
had to click it again, whereupon the slide might advance once, twice,
or not at all. Obviously not useful.
Realizing that I'd been plugged into AC earlier in the day, and now
was running on battery, I plugged in the AC adaptor. And sure enough,
the presenter worked fine, no delays or glitches. So battery was the issue.
What's different about running on batteries?
I immediately suspected laptop-mode, which sets different power profiles
to help laptops save battery life when unplugged.
The presenter acts as a USB keyboard, sending key events like PAGE DOWN,
and on other distros (specifically Arch Linux) I've had problems with
USB keyboard devices disappearing when laptop-mode is active.
So I moved /etc/init.d/laptop-mode out of the way to disable it,
and rebooted. Tried the presenter again: no improvement.
But it was laptop-mode anyway.
Apparently even though /etc/init.d/laptop-mode says in its header
that its purpose is to start and stop laptop-mode, apparently
laptop-mode starts even without that file.
The key is the configuration file
/etc/laptop-mode/conf.d/usb-autosuspend.conf,
where I changed the line
CONTROL_USB_AUTOSUSPEND="auto"
to
CONTROL_USB_AUTOSUSPEND=0
In theory, I should have been able to do
service laptop-mode restart
to test it,
but I didn't trust that since I'd just established that
/etc/init.d/laptop-mode didn't actually control laptop-mode.
So I rebooted.
And the presenter worked just fine!
I was able to give my talk that afternoon without plugging in the AC cord.
Ironically, this particular talk was on giving tech talks, and one of
my points was that being prepared and practicing beforehand is
critical to giving a good talk. I'm sure glad I did that extra
practice run with the presenter and no power cord!
Tags: linux, laptop, speaking
[
16:13 Nov 03, 2013
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Fri, 01 Nov 2013
We got started on Halloween a little late this year. It turns out that
by the afternoon of the 31st, you can't buy a pumpkin any more -- the
stores are all out of them.
We looked around -- what might we be able to use instead?
And lit upon something round, a little too small but not by much:
We had to find smaller hole saw bits than usual to cut the eyes
and mouth, since this was just a mini watermelon.
It turns out a mini watermelon has a very thin rind compared to a pumpkin.
But the fruit is a lot easier to scrape out (and tastes and smells a
lot better, too!) than pumpkin strings and seeds.
And the insides of the mouth are nicely red.
It comes out looking pretty good once it's lit, too!
Most years, we start with an actual pumpkin before we embark on our
annual Pumpkin
Trepanning operation (described in detail here).
In case you're curious, that stand we use for the pumpkins started
life as a 4-1/4-inch homebuilt telescope that was supposed to be a
mini model of the Hale
200-inch telescope at Mt Palomar. But we never finished grinding the
mirror -- grinding a 4.25" mirror takes almost as long as grinding
an 8" one, and when you're one what do you have? A 4.25" scope.
But the micro-Hale does make a pretty good jack-o-lantern stand.
Alas, our efforts this year were mostly for naught -- it was one of those
years when nobody's trick-or-treating. We only got one pair of
kids all evening. Anybody want some extra candy?
Tags: halloween, pumpkin, watermelon, trepanning
[
11:26 Nov 01, 2013
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