This how-to guide assumes you already completed the steps described in the 5-minute getting started experience. To test that the Nextmv CLI is correctly configured, you can optionally run the following command on your terminal. It will get some files that are necessary to work with the Nextmv Platform. You can see the expected output as well.
The Nextmv Software Development Kit (SDK) lets you automate any operational decision in a way that looks and feels like writing other code. It provides the guardrails to turn your data into automated decisions and test and deploy them into production environments.
Introduction
This guide will walk you through our unique-matrix-measure
template. Apps running in our app environment are self-contained and thus, have no access to outside resources while the app is running, all needed information needs to be passed within the input data. The input data size can become quite big and in this guide we will show you a method to reduce this data size. The requirement for this method to work is that you have many stops at the same location. To get the template, simply run the following commands.
You can check that all files are available in the newly created unique-matrix-measure
folder. Running the tree
command, you should see the file structure.
README.md
gives a short introduction to the routing problem and shows you how to run the template.go.mod
andgo.sum
define a Go module and are used to manage dependencies, including the Nextmv SDK.input.json
describes the input data for a specific routing problem that is solved by the template.license
contains the Apache License 2.0 under which we distribute this template.main.go
contains the actual code of the Nextmv routing app.- The
unique-matrix-measure.code-workspace
file should be used to open the template in Visual Studio Code. It is pre-configured for you so that you can run and debug the template without any further steps.
Now you can run the template with the Nextmv CLI, reading from the input.json
file and writing to an output.json
file. The following command shows you how to specify solver limits as well. You should obtain an output similar to the one shown.
Note that transient fields like timestamps, duration, versions, etc. are represented with dummy values due to their dynamic nature. I.e., every time the input is run or the version is bumped, these fields will have a different value.
Now we will show you, step by step, what the code inside the main.go
achieves.
Dissecting the routing app
The first part of the main.go
defines a package name, imports packages required, and defines a main
function which is the starting point for the app. In the main
function the Run
function from the Nextmv run
package is being called. This function executes a solver which is passed in the form of the solver
function further down in the file.
Before we look into the solver
function, we will examine the different structs that represent the needed data used by the app.
The Input
The input
struct lists the required input fields, Stops
and Vehicles
, Starts
and Ends
(both optional), as well as fields for UniquePoints
and UniqueMatrix
. UniquePoints
is a unique set of locations that need to be visited. And UniqueMatrix
represents a matrix of costs for going from each of the unique points to another. Stops
describes the list of locations to visit. It does that by referencing the 0-based index to the set of UniquePoints
. For that reason all those stops are represented by the stop
struct which holds only an ID
and the aforementioned Reference
to the UniquePoints
array. Vehicles
is an array of vehicle IDs.
The Solver
The solver
function is where the model is defined. The function's signature adheres to the run.Run
function we saw earlier already.
When you first ran the template you passed in the parameter -runner.input.path
followed by the path to an input file. This file is automatically parsed and converted to our input
struct. Other option arguments are also interpreted automatically and passed to the solver as an Options
struct.
Similar to the options you passed in when you ran the template, -limits.duration
and -diagram.expansion.limit
you can also set these values directly in your main.go
if you'd prefer not to pass them from the command line.
To be able to run the routing model we first need to convert the unique matrix into a full matrix the way the solver expect it. Before we start doing this, we will do some basic validation on the data to make sure that it is complete.
The checkInput
function validates that the UniqueMatrix
represents size-wise the UniquePoints
and that, if given, the Starts
and Ends
have the length of the Vehicles
which is a requirement of the routing engine.
Next we will create a new matrix fullMatrix
which has the size the solver requires. The solver require this size because it needs to calculate costs to each location, including the start and end location of each vehicle.
Next we create a helper variable joinedStops
which holds all stops from the input: Stops
, Starts
and Ends
. This will make it easier to access the required data by index. The code for joining the stops looks like this:
We first set each stop to have a reference of -1
. We do this because we need to detect if Starts
or Ends
are present. Without setting the default value to -1
all references would have a reference to 0
which is a valid reference index. Note that we are adding the Starts
and Ends
alternating because the solver requires them to be in this format: [stop-1, ..., stop-n, vehicle-1-start, vehicle-1-end, ..., vehicle-m-start, vehicle-m-end]
Now we loop over the each row and each cell in a row of the fullMatrix
to fill the matrix with the correct costs. Because the joinedStops
holds the stops in the correct order we can simply access the stops there and get the references to the UniquePoints
which at the same time are the indices for the UniqueMatrix
. If we find a reference of -1
we know that this is value is not given and we skip over, leaving the default value of 0
in the fullMatrix
untouched.
Before we can pass all of our data into the routing engine, we need to make it compatible with it. This means we need to pass the fullMatrix for each vehicle as an ByIndex measure, the stops may not use a reference to a location but have the location directly incorporated as its position, and the starts and ends need to be passed in as positions.
With all the data prepared we create a new routing engine:
Returning the solver
Finally, we return a solver
for our router
passing in options that were given at the very beginning by the calling function. This solver is then executed by the run.Run
function from the beginning.
For further understanding of how the router
engine works as part of the route
package, check out the route package how-to guide and the technical reference.