# C[omp]ute

Welcome to my blog, which was once a mailing list of the same name and is still generated by mail. Please reply via the "comment" links.

Always interested in offers/projects/new ideas. Eclectic experience in fields like: numerical computing; Python web; Java enterprise; functional languages; GPGPU; SQL databases; etc. Based in Santiago, Chile; telecommute worldwide. CV; email.

© 2006-2015 Andrew Cooke (site) / post authors (content).

## [Link, Bike] Cheap Cycling Jerseys

From: andrew cooke <andrew@...>

Date: Thu, 4 Jan 2018 20:13:58 -0300

I just received this jersey from Amazon and it seems pretty good (nice
fit, vibrant colours - no idea how durable yet)

https://www.amazon.com/gp/product/B06XXXJVBL

But then I realised that teh same jerseys are available cheaper on
Aliexpress.

Here are my favourites so far (I should get a Pinterest):

https://www.aliexpress.com/item/MILOTO-2017-Cycling-Jersey-Tops-Summer-Racing-Cycling-Clothing-Ropa-Ciclismo-Short-Sleeve-mtb-Bike-Jersey/32811819833.html

https://www.aliexpress.com/item/Tour-De-Italy-D-ITALIA-2016-Cycling-Jersey-short-sleeve-cycling-shirt-Bike-bicycle-clothes-Clothing/32795569586.html
(but select the dark one with a pink stripe).

https://www.aliexpress.com/store/product/2016-Summer-Cycling-Jersey-short-sleeve-cycling-shirt-Bike-bicycle-clothes-Clothing-Ropa-Ciclismo/2932053_32796720854.html
(and, same link, select the grey/green/blue one; also maybe the light
blue one).

Andrew

## Previous Entries

### [Link, Music] Music To Steal 2017

From: andrew cooke <andrew@...>

Date: Sun, 17 Dec 2017 12:18:23 -0300

https://www.theguardian.com/music/2017/dec/17/hidden-gems-2017-albums-may-have-missed

https://pitchfork.com/topics/the-best-music-of-2017/

Andrew

### [Link, Future] Simulated Brain Drives Robot

From: andrew cooke <andrew@...>

Date: Tue, 12 Dec 2017 08:42:24 -0300

http://www.sciencealert.com/scientists-put-worm-brain-in-lego-robot-openworm-connectome

A simulated worm's brain drives a robot.

I have been re-reading William Gibson's work.  This just seemed so on
the money.

Andrew

### [Link, Computing] Learned Index Structures

From: andrew cooke <andrew@...>

Date: Tue, 12 Dec 2017 08:41:20 -0300

https://arxiv.org/pdf/1712.01208v1.pdf

(frankly I think this paper i smore important than credited in that
discussion - we'll see...).

Andrew

### [Bike] Exercise And Fuel

From: andrew cooke <andrew@...>

Date: Sat, 9 Dec 2017 15:40:35 -0300

"Fuel" rather than "Nutrition" because I am thinking mainly about the
calories.  The following thoughts were prompted by a paper I read
online which I can no longer find - repeating the search leads me to
other, more complex studies.  So not only do I not have a reference,
but what follows may be oversimplified.

Glycogen v Fat

When exercising aerobically we burn fuel from three main sources:

* Fat reserves, which are virtually unlimited (for most of us), but
slow to access.  Fat reserves are stored throughout the body.

* Glycogen reserves, which are limited but easier to access.
Glycogen reserves are local to the muscle being used.

* External sources (ie eating).

At low exertion levels the body preferentially burns fat.  But as the
power output increases this cannot be accessed quickly enough and the
proportion of glycogen increases.

Since the amount of glycogen is limited this explains "bonking" or
"the wall" - the unpleasant experience of glycogen reserves being
depleted.  As you would expect, this can be postponed by:

* Lowering power output (and so reducing both absolute and relative
burn rates for glycogen)

* Eating while exercising.  An external source of fuel will displace
the need for glycogen / fat burning, but is limited in volume (you
simply can't eat that much while exercising) and delayed (it takes
time to digest what you eat).

Given all the above it is clear that the need to eat while doing
endurance exercise will depend on both the size of glycogen reserves
and the power levels required - both of which can vary strongly from
person to person.

Glycemic Complexity

One factor briefly mentioned above is digestion time.  High glycemic
index carbs are those that are easy to digest and provide a large
amount of energy for a short time, while low index carbs are slow to
digest, providing a lower, more extended boost.

Curiously, the index doesn't match the difference between simple and
complex sugars: white bread (starch) apparently has a higher index
than sugar (sucrose).

This is important for me because, it turns out, the time I stop riding
to eat is quite significant in how well I perform (over longer
segments on Strava).  So I guess I should look eating porridge before
a ride...

Andrew

### [Maths, Link] Dividing By Zero

From: andrew cooke <andrew@...>

Date: Sat, 4 Nov 2017 09:53:34 -0300

https://www.reddit.com/r/askscience/comments/7akmy2/why_cant_we_have_a_system_for_dividing_by_zero/

https://en.wikipedia.org/wiki/Wheel_theory

Andrew

### [Book, Review] Ray Monk - Ludwig Wittgenstein: The Duty Of Genius

From: andrew cooke <andrew@...>

Date: Fri, 3 Nov 2017 08:59:38 -0300

This is a curious mix of a book.

On the one hand, it's well written - clear and coherent.  A deftly
constructed account of Wittgenstein's life, painting an apparently
complete picture of its subject.

On the other - at least to this reader - it fails to explain exactly
why Wittgenstein was (and is) so admired.  Trudging through the
details of his obsessions, neuroses and fears, you begin to wonder why
you are spending so much time (~600 pages) on such an unpleasant
person:

* Someone who gave up a huge amount of wealth, but continued to
assume the privilege and standing of his birth, repeatedly relying
on the influence of friends in high places.

* Someone pathetically useless in social situations who felt
qualified to tell others how they should behave.  Who was incapable
of being a good teacher yet encouraged others to follow the same
path.

* Someone who intimidated and brow-beat.  Whose philosophy appears to
be "I am right, you are wrong, but I cannot explain why."

* Someone who felt they were making major contributions to the
philosophy of mathematics yet lacked the technical ability to
understand Godel's work.

* Someone who could only connect emotionally with those who were
younger, weaker, and easier to intimidate.

A thoroughly unlikeable man.

I am not arguing that only the nicest people should have biographies,
but perhaps the author should more clearly explain why they are
interesting.  Reports of "genius" from others in the same privileged
milieu are not enough.

Andrew

### [Link, Bike, Computing] Evolving Lacing Patterns

From: andrew cooke <andrew@...>

Date: Tue, 31 Oct 2017 18:53:34 -0300

http://master.matsemann.com/

Andrew

### [Jam] Strawberry and Orange Jam

From: andrew cooke <andrew@...>

Date: Sat, 28 Oct 2017 22:07:03 -0300

Made this about a month ago, but just realised I hadn't made a note of
the ingredients.  So, before I forget:

2kg Strawberries
1kg Oranges
2kg Sugar

Weights are prepared fruit.  Wash the strawberries, remove the leaves,
and chop roughtly.  Wash the oranges well (to remove wax), cut off the
rind thinly and chop to fine pieces, remove the pith and cut out the
segments - cook the fruit (not the pith) and chopped rind.

The taste was difficult to imagine beforehand, but in retrospect is
obvious - orangey strawberry.  Imagine a strawberry jam made with
orange liquer, for example.

(The reason for this odd combination is that strawberries appear early
and there's not much else to combine them with).

Saw peaches at the market today, for the first time this year (which
reminded me to write this) so will make some peach jam next weekend :)

Andrew

### [Chile, Privacy] Biometric Check During Mail Delivery

From: andrew cooke <andrew@...>

Date: Thu, 26 Oct 2017 21:06:56 -0300

I live in Santiago, Chile, and just received an Amazon delivery, via
Landmark postal.  I don't know what company handles the delivery
locally, but the delivery person carried a plastic tray that held a
smartphone and a fingerprint reader.  He asked for my RUT (the state
ID number, used throughout Chilean society as a way of identifying
people, and quite a normal request when a registered package is
delivered), entered that number into the phone, which then paused
(making a request to a server for appropriate data?) before prompting
me to place my index finger on the reader.  Apparently that validated
that I was who I claimed to be and I received the package.

You may wonder where the fingerprint data comes from.  A similar
process is used to identify users when claiming medical insurance here
(eg when paying for a visit to the doctor).  So perhaps that company
is now sharing data?  Or maybe this is separate and this first scan
was not verification, but entering me into a new database?  Unlike the
print with details of who was recording the data, or what conditions I
was implicitly agreeing to.

(Our identity cards also carry fingerprint data, but I am pretty sure
that is a thumb print, which has legal conotations here.  For example,
at a notary, I have to both sign and thumb-print important documents).

Andrew

### [Link, Chile, Spanish] Article on the Chilean Drought

From: andrew cooke <andrew@...>

Date: Thu, 26 Oct 2017 21:05:18 -0300

http://ingenieria.uchile.cl/noticias/138171/columna-de-opinion-de-la-megasequia-a-la-mediasequia

Andrew

### [Bike] Extended Gear Ratios, Shimano XT M8000 (24/36 Chainring)

From: andrew cooke <andrew@...>

Date: Wed, 25 Oct 2017 10:30:48 -0300

I've been frustrated with the highest gear of my Shimano 2x11 XT M8000
drivetrain, which uses the lowest stock 24/34 chainrings and an 11-42
cassette (with a 2X front pull, high cage derailleur and the long SGS
rear derailleur).  Compared to my old 3x9 setup I spin out
significantly earlier on downhills (the gearing on the new 2x11 was
chosen to match the lowest gear on the 3x9).

So I tried changing the front chainrings to 24/36, and have been very
pleasantly surprised by the results.

First of all, everything works fine - I noticed no difference in the
quality of the gear changes, despite the front derailleur being
specified for a maximum change of 10 teeth.

Second, the difference feels like a BIG improvement, despite the
figures (below).  This was surprising and I have the following
tentative explanations:

* Maybe Chilean roads, or at least the routes I ride, are built so
that the steepest parts were just outside my gear range (and are
now just inside)?

* Maybe there's a "terminal velocity" where wind resistance (for me,
on my bike, in my riding position) imposes an upper speed limit
that was just beyond my original gearing, and that is now
achievable.

* Maybe it's just the shock of the new and I am over-estimating its
significance.

Whatever the reason, this feels like a big improvement: I have new PRs
(without even trying!) and can pedal pretty much constantly on my
common routes.

The numbers, however, are not startlingly different.  Below I give the
log of the gain ratio for various combinations of gears.  You don't
need to know what it means - just that it's a measure of how "fast"
each gear is:

Old 24/34     New 24/36

big top        -0.69         -0.63
big top-1      -0.86         -0.80
big top-2      -1.00         -0.94
big top-3      -1.12         -1.07

small top      -1.04         -1.04

Which shows that:

* The additional range is small - about 1/3 of a gear (0.06 v 0.17)

* Previously, the small chainring ratios sat nicely between the big
chainring ratios, effectively giving very closely spaced gears (if
you constantly switched between chainrings).  That is no longer the
case.

Note that the rear derailleur capacity is 47, so there is no problem
there - the only limitation is the front derailleur.

Disclaimers:

* I made the change at the same time as changing the front derailleur
(the spring broke on the previous one), rear derailleur (bent) and
rear cassette (worn).  So the entire drivetrain is new (apart from
the cranks and shifters - I also changed the cables).

* My bike has a Boost rear hub but normal front derailleur mount /
bottom bracket (this is standard for 2017 Cotic Soul).  So my
chainline is not "correct".

Andrew