-
After a harrowing chase, Ethic, Hedge,
and their new ally Lemma
-
find themselves in a cavernous
control room.
-
Here the last artifact—
the Node of Memory—
-
is suspended within a force field
and powering a supercomputer.
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Ethic is about to deactivate the force
field when Lemma stops her.
-
She explains, a decade ago, she was
assigned a research task:
-
to use the world machine to create
something that would make everyone happy.
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After many failed attempts, Lemma
discovered a compound that, when ingested,
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made people motivated, happy, creative,
loving…in short, their best selves.
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It was rushed into production.
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Soon, the entire nation’s food supply came
from Huxenborg,
-
with the compound mixed in.
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The first year was paradise.
-
The second, not so much.
-
Side-effects began to emerge: memory-loss,
listlessness, and self-absorption.
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In the third year, the government
dissolved,
-
leaving the robots running everything
in a self-sustaining loop.
-
By this point things were too far gone
for Lemma to reverse.
-
People had become dependent on the
compound,
-
and the few who refused it formed a
resistance to try to fix things.
-
It took 10 years for Lemma to find a cure.
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This factory contains everything she’ll
need to make it,
-
but the second they take the Node
of Memory,
-
the security system will alert the robots,
and they’ll have to run.
-
If, instead, they first reconfigure the
factory to manufacture the cure,
-
the people can be saved.
-
Lemma has the whole factory redesign
planned out.
-
The problem is… it’s a little
hard to read.
-
Her schematic shows all the steps in the
manufacturing process
-
needed to make the cure.
-
An arrow from “add nitric acid” to
“shake vigorously”
-
means that the acid addition has to
happen before shaking.
-
If a single step is performed
out of order,
-
the cure won’t work, or worse.
-
There aren’t any circular references,
where step A requires step B
-
and step B eventually requires step A.
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Here’s where Ethic and Hedge come in.
-
Lemma needs Hedge to translate the
tangled diagram into a sequence of steps.
-
That’ll be the order that things happen
in the factory.
-
Once input into the central computer,
-
the factory will reassemble
itself as instructed.
-
Hedge’s ability to store information in a
table will help here.
-
So how does Ethic program Hedge
to turn out a correct sequence
-
that can reconfigure the factory?
-
Pause now to figure it out yourself.
-
Rules in 3
-
Rules in 2
-
Rules in 1
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Hint in 3
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Hint in 2
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Hint in 1
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It may help to first think about this
problem as a human, rather than a machine.
-
Given this diagram, it’s clear to start
with getting a bowl,
-
since no arrows point to it.
-
How might you mark up the diagram
to figure out what to do next?
-
Pause now to figure it out yourself.
-
Solution in 3
-
Solution in 2
-
Solution in 1
-
Diagrams like the one Lemma has drawn
are called directed acyclic graphs.
-
A graph is a representation of data
that shows different elements
-
and how they’re related to each other.
-
Directed means that direction matters—
as indicated by the arrows.
-
Here A leads to B, but B
doesn’t lead to A.
-
And acyclic means that there aren’t
any loops.
-
Which is fortunate, because if there were,
this problem wouldn’t be solvable.
-
There’s a simple way to navigate the
graph as a human:
-
start with a step that doesn’t have any
arrows pointing to it.
-
Once you do that, cross out that step
and all arrows leading from it.
-
Choose another step with no arrows
pointing to it,
-
and repeat until you’ve hit every step.
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There are two things here that are tricky
to translate for a robot.
-
First, how do you keep track of the
information?
-
And second, what do you do if there
are multiple options at the same time?
-
For the first challenge,
-
a convenient way for machines to
store information is in a table.
-
In this case, you can have Hedge list
every step in the headers
-
of both the rows and columns.
-
Then he can go through
the rows one at a time.
-
On the schematic, what points to mix?
-
Both shake and titrate.
-
So Hedge should make a mark in
both of their columns.
-
He can do the same for every row,
one at a time, to make a table like this.
-
Of course the full table
will be much bigger.
-
Like a human, Hedge will also
want to start
-
from one of the steps that has
no arrows pointing to it—
-
which is the same as having no marks
in its row.
-
If there’s more than one,
-
a convenient way to choose is to pick the
one that’s alphabetically earliest,
-
though other selection methods
can work just as well.
-
Next, Hedge can add that step to his
running-order list,
-
delete its entire column from the table—
-
thus removing all the times
it was a dependency––
-
and loop back to the start.
-
Because there are no circular
references in the graph,
-
each time we get here there’ll be at least
one step with no remaining dependencies.
-
Hedge can add the alphabetically earliest
to his running-order list,
-
remove it from the table, and loop
back to the start again.
-
So now we have a working loop,
-
and it’ll run through all the elements
in our table until none are left.
-
Hedge drifts back and forth over the
schematics,
-
and soon he starts spitting
out instructions,
-
which Ethic uses to configure the
assembly lines.
-
With the three working together,
-
they churn out thousands of doses
of the cure in no time.
-
Ethic finally plucks the Node of Memory
-
from its holding field and
trips the alarm.
-
Within seconds bots are everywhere.
-
As Ethic falls in shock, the Node
restores not only her own memories,
-
but reveals the last, missing pieces
of the puzzle.
-
Ethic built Hedge with a singular purpose:
-
to construct a maze that would protect the
world machine from a corrupt government.
-
But in her haste,
she made a critical mistake.
-
She forgot to set the condition
that would end the loop
-
which told Hedge how large
the maze should be.
-
So Hedge built and built until he
could build no longer.
-
And then he was conflicted.
-
He had to build a maze.
-
But he couldn’t build further without
hurting people
-
or flying over the Bradbarrier,
-
both forbidden by his programming.
-
So he wandered the land and searched
for a solution,
-
until he happened upon the Node of Power,
the Node of Creation,
-
and the Node of Memory.
-
He recognized their true,
collective power
-
to grant self-awareness
to those who lack it.
-
With all three he’d be able to change
his programming
-
and fulfill his drive to transform
the entire world into a giant maze.
-
It wouldn’t be easy:
-
the Nodes had safeguards to prevent
robots from taking and using them.
-
But if Hedge could find the right human
-
and manipulate her with the
promise of a heroic quest…
-
well that would be a different story.
-
A very different story.