R: Read and Write Files for 'pomdp-solve'

read_write {pomdpSolve}

R Documentation

Read and Write Files for 'pomdp-solve'

Description

Read and write files for the pomdp-solve executable.

Usage

read_alpha_file(file)

read_pg_file(file)

read_belief_file(file)

write_grid_file(file, belief_points, digits = 7)

write_terminal_values(file, alpha, digits = 7)

Arguments

`file`	name of the file to read from or to write to.
`belief_points`	a numeric matrix with the number of states columns. Rows represent belief points.
`digits`	number of digits used to write files.
`alpha`	a numeric alpha vector with the length of the number of states.

Details

pomdp-solve uses text format for its input and output. The input is a POMDP file. The outputs are the following.

Value Function

The value function is returned as files with the extension .alpha in the format:

A
V1 V2 V3 ... VN

A
V1 V2 V3 ... VN

...

Where A is an action number and the V1 through VN are real values representing the components of a particular vector that has the associated action. The action number is the 0-based index of the action as specified in the input POMDP file. The vector represents the coefficients of a hyperplane representing one facet of the piecewise linear and convex (PWLC) value function. Note that the length of the lists needs to be equal to the number of states in the POMDP.

read_alpha_file() reads the V components from the file and returns a matrix.

Policy Graph

The policy graph is returned as a file with the extension .pg. Each line of the file represents one node of the policy graph and its contents are:

N A  Z1 Z2 Z3 ...
...

Here N is a node ID giving the node a unique name, numbered sequentially and lining up with the value function vectors in the corresponding output .alpha file above.

The A is the action number defined for this node; it is an integer referring to the the POMDP file actions by its 0-based index number. These are followed by a list of node IDs, one for each observation. Thus the list will have a length equal to the number of observations in the POMDP. This list specifies the transitions in the policy graph. The nth number in the list will be the index of the node that follows this one when the observation received is n.

read_pg_file() returns a data.frame with the nodes in the policy graph as rows.

Terminal Values

Terminal values can be specified as a single alpha vector.

Grid-based Solver Specific Files

The grid-based method can write the used belief points do disk (command line option -fg_save). The file can be read using read_belief_file().

A matrix with belief points can be written using write_grid_file(). This file can be used

Details about the file formats and pomdp-solve can be found in the References section.

See pomdp_solve() for examples.

Value

read_alpha_file() returns the value function (alpha vectors) as a matrix.
read_pg_file() returns the policy graph as a data.frame.
read_belief_file() returns a matrix if the solver wrote a belief file.
write_grid_file() returns nothing.
write_terminal_values() returns nothing.

References

Anthony R. Cassandra, pomdp-solve documentation, https://www.pomdp.org/code/index.html