Simulation parameters that are used to configure the simulation when calling setup(). More...

#include <creativity/CreativitySettings.hpp>

Public Attributes
uint32_t	readers = 100
	The number of readers in the simulation.

uint32_t	dimensions = 2
	The number of dimensions in the simulation.

double	boundary = 5.0
	The boundary in each dimension to use for simulation members. More...

double	book_distance_mean = 0.0
	An authored book will be located at a distance of \(mx\) from the author's location at the time of writing, where this value is \(m\) and \(x \sim \chi^2_1\). More...

double	book_quality_sd = 1.0
	The standard deviation of a book quality draw. More...

double	reader_step_mean = 0.5
	Between periods, readers take a random step of length \(mx\), where this value is \(m\) and \(x \sim \chi^2_1\). More...

double	reader_creation_shape = 0
	The "shape" parameter \(\beta\) of the reader effort. More...

double	reader_creation_scale_min = 0.0
	Reader.creation_scale values are drawn from \(U[a,b]\), where this value is the lower bound. More...

double	reader_creation_scale_range = 10.0
	Reader.creation_scale values are drawn from \(U[a,b]\), where this value is the size of the range `b-a`. More...

uint32_t	creation_time = 3
	The average length of time (in simulation periods) it takes to create a book. More...

double	creation_fixed = 100.0
	The fixed cost component of initial creation. More...

double	cost_market = 10.0
	The fixed cost of keeping a book on the market.

double	cost_unit = 1.0
	The unit cost of selling a copy of a book (note that only copies of books still on the market can be sold), which is also the cost of obtaining a pirated copy (but is then incurred by the recipient, rather than the author). More...

double	cost_piracy = 1.0
	The cost of receiving a pirated copy of a book, incurred by the recipient.

double	income = 1000.0
	The per-period external income readers receive. More...

eris::eris_time_t	piracy_begins = 101
	The period in which piracy becomes available. More...

Policy	policy = Policy::PublicSharing()
	The policy response(s) used to address piracy. More...

eris::eris_time_t	policy_begins = 201
	The period in which the policy response to piracy begins. More...

double	policy_public_sharing_tax = 10.0
	This is the lump-sum tax extracted from each user at the beginning of the period to fund the public sharing mechanism of author compensation. More...

double	policy_public_voting_tax = 10.0
	This is the lump-sum per-reader tax for public sharing with voting. More...

uint32_t	policy_public_voting_votes = 3
	The number of votes each reader receives in the public-sharing-with-voting regime. More...

double	policy_catch_tax = 10.0
	This is the lump-sum tax extracted from each user to fund the policing policy to catch and fine readers using piracy. More...

double	policy_catch_cost = 10.0
	The utility cost of being accused of piracy. More...

std::array< double, 3 >	policy_catch_fine {{25., 12.5, 12.5}}
	A person who gets caught and is guilty of piracy pays a fine of \(c_0 + c_1 #P + c_2 #P^2\), where \(#P\) is the number of pirated books the person obtained in the caught period. More...

std::array< double, 3 >	policy_catch_mu {{10., -.08, 0.}}
	For the "catch pirates" policy, the probability of being accused of piracy for obtaining \(x\) copies over the network equals the CDF of a \(\mathcal{N}(\mu, \sigma^2)\) distribution evaluated at \(x\); that is, \(\Phi\(\frac{x - \mu}{\sigma}\)\). More...

std::array< double, 3 >	policy_catch_sigma {{3., -.02, 0.}}
	Like `policy_catch_mu`, but for the quadratic coefficients of \(\sigma = c_0 + c_1 \tau + c_2 \tau^2\). More...

double	piracy_link_proportion = 0.1
	The number of sharing/friendship links as a proportion of the maxinum number of sharing links possible (which is \(\frac{R(R-1)}{2}\), where \(R\) is the number of readers). More...

double	prior_scale = 1.02
	The factor by which parameter standard deviations should be multiplied when using it as a prior for a subsequent period, after the initial burn-in period.

double	prior_scale_piracy = 2
	The factor by which to multiply standard deviations in the first piracy period. More...

double	prior_scale_policy = 2
	The factor by which to multiply standard deviations in the first policy response period. More...

double	prior_scale_burnin = 1.5
	The prior weight to use during the burn-in period; typically much larger than prior_scale so that the simulation results of pre-belief initial parameters have significantly less weight in readers' beliefs.

uint32_t	burnin_periods = 20
	The number of "burn-in" periods, during which priors are discounted at a higher rate. More...

uint32_t	prediction_draws = 100
	The number of model draws to use for prediction. More...

struct {
double prob_write = 0.1
	The probability that a reader writes a book. More...

double l_min = 0
	Initial book creation effort levels are distributed Uniform[`l_min`, `l_min+l_range`]. More...

double l_range = 100.0
	Initial book creation effort levels are distributed Uniform[`l_min`, `l_min+l_range`]. More...

double p_min = 4.0
	Initial book prices are distributed `cost_unit +` Uniform[`p_min`, `p_min+p_range`]. More...

double p_range = 30.0
	Initial book prices are distributed `cost_unit +` Uniform[`p_min`, `p_min+p_range`].

double prob_keep = 0.5
	The probability of a book being kept on the market for another period. More...

double keep_price = 0.5
	The relative price-above-marginal-cost of a book being kept on the market for another period. More...

int32_t belief_threshold = 5
	The minimum number of observations (relative to k) before a belief is used. More...

}	initial
	The values in this struct define fixed probabilities and distributions of simulation actions. More...

Detailed Description

Simulation parameters that are used to configure the simulation when calling setup().

Member Data Documentation

§ belief_threshold

int32_t creativity::CreativitySettings::belief_threshold = 5

The minimum number of observations (relative to k) before a belief is used.

Before reaching this threshold, actions are governed by the initial values, above.

This setting also governs the use of the ProfitStream beliefs of different lengths: authors will not use ProfitStream belief models that do not have at least this number of observations. (For example, if this setting equals 2 and there are ProfitStream beliefs for 1-, 2-, and 4-period old books, with 15, 7, and 5 observations, only the 1- and 2-period models will be used.)

Note that partially informative models (i.e. those with fewer than K linearly-independent observations) are never used, so setting this to a value smaller than 0 has no effect, and often the effective minimum threshold is noticeably higher than 0 (particularly when the model contains dummy or other small integer values).

§ book_distance_mean

double creativity::CreativitySettings::book_distance_mean = 0.0

An authored book will be located at a distance of \(mx\) from the author's location at the time of writing, where this value is \(m\) and \(x \sim \chi^2_1\).

This distance thus has the given mean and a standard deviation of \(\sqrt{2}m\).

The final location is drawn from a uniform distribution over all points with the given distance from the author.

If this value is 0, the book is located exactly at the author's position at the time of writing and no draw is performed.

§ book_quality_sd

double creativity::CreativitySettings::book_quality_sd = 1.0

The standard deviation of a book quality draw.

When a reader obtains a book, his subjective quality is drawn from \(N(Q, s)\), where \(Q\) is the book's base quality as decided by the author and \(s\) is this setting.

As long as this setting is positive, this means book quality is subjective; if 0, all readers perceive the book as having the same quality.

§ boundary

double creativity::CreativitySettings::boundary = 5.0

The boundary in each dimension to use for simulation members.

Must be a positive value. The the exact boundary is calculated from the simulation density at the initialization of the simulation as the density could theoretically change during the simulation, but the boundary defines the world and so is fixed forever.

§ burnin_periods

uint32_t creativity::CreativitySettings::burnin_periods = 20

The number of "burn-in" periods, during which priors are discounted at a higher rate.

§ cost_unit

double creativity::CreativitySettings::cost_unit = 1.0

The unit cost of selling a copy of a book (note that only copies of books still on the market can be sold), which is also the cost of obtaining a pirated copy (but is then incurred by the recipient, rather than the author).

Note that, if changing this, it is advisable to also consider changing parameters.initial.p_min.

§ creation_fixed

double creativity::CreativitySettings::creation_fixed = 100.0

The fixed cost component of initial creation.

This plus the expended effort level is incurred to create.

§ creation_time

uint32_t creativity::CreativitySettings::creation_time = 3

The average length of time (in simulation periods) it takes to create a book.

If 0, books are created instantly; otherwise books take this value -1/+0/+1 with equal probability of each (so that this is still the mean creation time). (The randomness helps avoid strongly cyclical authorship behaviour)

§ income

double creativity::CreativitySettings::income = 1000.0

The per-period external income readers receive.

Effort spent creating a book in a period is subtracted from this amount.

§ initial

struct { ... } creativity::CreativitySettings::initial

The values in this struct define fixed probabilities and distributions of simulation actions.

This is needed because, in the initial simulation periods, readers only have noninformative beliefs which are completely useless for predicting anything in the model.

Instead, readers act randomly until useful beliefs are established, according to the values that follow.

§ keep_price

double creativity::CreativitySettings::keep_price = 0.5

The relative price-above-marginal-cost of a book being kept on the market for another period.

For example, if this is 0.75, the current price is 3, and parameters.cost_unit is 1, then the new price will be 1 + 0.75*(3-1) = 2.5.

§ l_min

double creativity::CreativitySettings::l_min = 0

Initial book creation effort levels are distributed Uniform[l_min, l_min+l_range].

Readers without sufficiently informed quality beliefs use the mean of the resulting quality distribution for initial purchasing decisions.

§ l_range

double creativity::CreativitySettings::l_range = 100.0

Initial book creation effort levels are distributed Uniform[l_min, l_min+l_range].

Readers without sufficiently informed quality beliefs use the mean of the resulting quality distribution for initial purchasing decisions.

§ p_min

double creativity::CreativitySettings::p_min = 4.0

Initial book prices are distributed cost_unit + Uniform[p_min, p_min+p_range].

Note that initial book quality, at default creation shape/scale and l_min/l_range settings, can take a value anywhere from 0 to 46.15, and has a mean of 20.14.

§ piracy_begins

eris::eris_time_t creativity::CreativitySettings::piracy_begins = 101

The period in which piracy becomes available.

If 0, piracy is never invented. (Since t=0 is the initial setup (without any actions), set to 1 to having sharing become available immediately).

§ piracy_link_proportion

double creativity::CreativitySettings::piracy_link_proportion = 0.1

The number of sharing/friendship links as a proportion of the maxinum number of sharing links possible (which is \(\frac{R(R-1)}{2}\), where \(R\) is the number of readers).

Links as assigned randomly between agents when the simulation is initially set up, with an equal probably of each possible link being selected.

The default is 10% coverage of maximum potential links (rounded to the nearest integer). In the default 100-reader simulation, this is 495 links.

The value must be in \([0, 1]\).

§ policy

Policy creativity::CreativitySettings::policy = Policy::PublicSharing()

The policy response(s) used to address piracy.

Supported policies (which may be combined) are:

public sharing: public tax for public provisioning and sharing; when the policy response begins, a PublicTracker agent is created that distributes copies of books to anyone at marginal cost. Authors are compensated in proportion to the number of downloads of their works from a per-reader lump sum tax.
catch pirates: public tax for catching people downloading illegal copies. A lump sum tax is collected and goes towards the policing effort, with a larger tax resulting in a higher probability of detection.
public voting: public tax for public provisioning and sharing with reader votes. This is like public sharing, but instead of awarding the collected prize in proportion to downloads, readers cast votes for their favourite works in a period and the tax is redistributed proportionally to votes received.

Other values are reserved for future use.

§ policy_begins

eris::eris_time_t creativity::CreativitySettings::policy_begins = 201

The period in which the policy response to piracy begins.

Which response is used depends on the policy parameter.

§ policy_catch_cost

double creativity::CreativitySettings::policy_catch_cost = 10.0

The utility cost of being accused of piracy.

This is incurred by everyone who is accused of piracy, regardless of whether or not they are guilty (since the probability of being caught even with no piracy is > 0). If guilty, the reader pays an additional fine, determined by policy_catch_fine. This component of the cost is simply a cost, it is not a fine being transferred, unlike policy_catch_fine.

§ policy_catch_fine

std::array<double, 3> creativity::CreativitySettings::policy_catch_fine {{25., 12.5, 12.5}}

A person who gets caught and is guilty of piracy pays a fine of \(c_0 + c_1 #P + c_2 #P^2\), where \(#P\) is the number of pirated books the person obtained in the caught period.

Thus a caught individual who obtained 3 pirated copies pays \(c_0 + 3 c_1 + 9 c_2\).

The fine amount is removed from the reader's utility (as a proxy for the reader's wealth, which is outside this model), and is redistributed to the authors of the pirated works. Specifically, the fine is divided into \(#P\) equal shares and each share is transferred to the author of each pirated work. (It is possible for a single author to receive multiple shares, if multiple copies of his works were pirated by the fined reader).

The default is a fine of 50 for the first, +50 for the second, +75 for the third, etc. (so a total fine of 50, 100, 175, 275, ...).

§ policy_catch_mu

std::array<double, 3> creativity::CreativitySettings::policy_catch_mu {{10., -.08, 0.}}

For the "catch pirates" policy, the probability of being accused of piracy for obtaining \(x\) copies over the network equals the CDF of a \(\mathcal{N}(\mu, \sigma^2)\) distribution evaluated at \(x\); that is, \(\Phi\(\frac{x - \mu}{\sigma}\)\).

\(\mu\) and \(\sigma\) themselves are quadratic functions of the per-user piracy detection expenditure, i.e., functions of policy_response_tax.

This array contains the constant, linear, and quadratic coefficients that define \(\mu = c_0 + c_1 \tau + c_2 \tau^2\), where \(\tau\) is the policy_response_tax value. Note that the probability of detection equals 50% at \(\mu\), 5% at \(\mu - 1.96 \sigma\), 95% at \(\mu + 1.96\). The default is \(\mu = 10 - 0.5 \tau\).

Note that the probability of being caught is never 0, even for an individual who does not pirate; such false accusations can still incur a cost, or can be ignored, depending on the policy_catch_cost variable.

The default for this an mu are selected with a range of tau of (0, 100] in mind: close to 0, the probability of catching someone who doesn't pirate is very close to 0, the 50% detection is at 10 pirated copies in a period, and the 95% is at 16 (i.e. the probability is the CDF of N(10,3)). At the upper end, the CDF is N(2, 1), i.e. non-pirates are false accussed just under 5% of the time, people pirating 2 are caught 50% of the time, and 95% is hit after pirating 4 copies.

§ policy_catch_sigma

std::array<double, 3> creativity::CreativitySettings::policy_catch_sigma {{3., -.02, 0.}}

Like policy_catch_mu, but for the quadratic coefficients of \(\sigma = c_0 + c_1 \tau + c_2 \tau^2\).

The default is \(\sigma = 3 - .02 \tau\). Note that this will fail (immediately) if tau is >= 150.

See also: policy_catch_mu

§ policy_catch_tax

double creativity::CreativitySettings::policy_catch_tax = 10.0

This is the lump-sum tax extracted from each user to fund the policing policy to catch and fine readers using piracy.

Has no effect when the catching policy is not enabled.

§ policy_public_sharing_tax

double creativity::CreativitySettings::policy_public_sharing_tax = 10.0

This is the lump-sum tax extracted from each user at the beginning of the period to fund the public sharing mechanism of author compensation.

Has no effect when public sharing is not enabled. Must be >= 0; if 0, no redistribution happens.

§ policy_public_voting_tax

double creativity::CreativitySettings::policy_public_voting_tax = 10.0

This is the lump-sum per-reader tax for public sharing with voting.

Has no effect when public sharing with voting is not enabled. Must be strictly greater than 0.

§ policy_public_voting_votes

uint32_t creativity::CreativitySettings::policy_public_voting_votes = 3

The number of votes each reader receives in the public-sharing-with-voting regime.

Voters cast votes in (rough) proportion to the net utility they received from reading each public book obtained in the current period.

For example, if a reader obtained 4 book copies, and received net utility of 10, 5, 2, 1, if given 4 votes, he would cast 3 votes for book 1, and 1 vote for book 2; with 18 votes he would cast 10, 5, 2, 1.

§ prediction_draws

uint32_t creativity::CreativitySettings::prediction_draws = 100

The number of model draws to use for prediction.

Higher values yield more "accurate" predictions, but lower values may be desirable to introduce more random agent behaviour.

§ prior_scale_piracy

double creativity::CreativitySettings::prior_scale_piracy = 2

The factor by which to multiply standard deviations in the first piracy period.

This value overrides prior_scale in the piracy_begins period.

§ prior_scale_policy

double creativity::CreativitySettings::prior_scale_policy = 2

The factor by which to multiply standard deviations in the first policy response period.

This value overrides prior_scale in the policy_response_begins period.

§ prob_keep

double creativity::CreativitySettings::prob_keep = 0.5

The probability of a book being kept on the market for another period.

§ prob_write

double creativity::CreativitySettings::prob_write = 0.1

The probability that a reader writes a book.

§ reader_creation_scale_min

double creativity::CreativitySettings::reader_creation_scale_min = 0.0

Reader.creation_scale values are drawn from \(U[a,b]\), where this value is the lower bound.

Defaults to 0.

See also: Reader.creation_scale

§ reader_creation_scale_range

double creativity::CreativitySettings::reader_creation_scale_range = 10.0

Reader.creation_scale values are drawn from \(U[a,b]\), where this value is the size of the range b-a.

Defaults to 10 (so the values are drawn from U[0,10]).

§ reader_creation_shape

double creativity::CreativitySettings::reader_creation_shape = 0

The "shape" parameter \(\beta\) of the reader effort.

See also: Reader.creation_shape

§ reader_step_mean

double creativity::CreativitySettings::reader_step_mean = 0.5

Between periods, readers take a random step of length \(mx\), where this value is \(m\) and \(x \sim \chi^2_1\).

This value has mean \(m\) and standard deviation \(\sqrt{2} m\). If 0, readers remain at their initial positions forever.

The final location is selected from a uniform distribution over all points with the given distance from the reader's initial position.

The default is 0.5.

Collaboration diagram for creativity::CreativitySettings:

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The documentation for this struct was generated from the following file:

creativity/CreativitySettings.hpp

Public Attributes