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Solve Graph - Multiple Routing (NYC Taxi)

The following is a complete example, using the Python API, of solving a graph created with NYC Taxi data for a multiple routing problem via the /solve/graph endpoint. For more information on Network Graphs & Solvers, see Network Graphs & Solvers Concepts.

Prerequisites

The prerequisites for running the multiple routing solve graph example are listed below:

Python API Installation

The native Kinetica Python API is accessible through the following means:

  • For development on the Kinetica server:
  • For development not on the Kinetica server:

Kinetica RPM

In default Kinetica installations, the native Python API is located in the /opt/gpudb/api/python directory. The /opt/gpudb/bin/gpudb_python wrapper script is provided, which sets the execution environment appropriately.

Test the installation:

/opt/gpudb/bin/gpudb_python /opt/gpudb/api/python/examples/example.py

Important

When developing on the Kinetica server, use /opt/gpudb/bin/gpudb_python to run Python programs and /opt/gpudb/bin/gpudb_pip to install dependent libraries.

Git

Python 2.7 (or greater) is necessary for downloading the API from GitHub:

  1. In the desired directory, run the following but be sure to replace <kinetica-version> with the name of the installed Kinetica version, e.g., v7.0:

    git clone -b release/<kinetica-version> --single-branch https://github.com/kineticadb/kinetica-api-python.git
    
  2. Change directory into the newly downloaded repository:

    cd kinetica-api-python
    
  3. In the root directory of the unzipped repository, install the Kinetica API:

    sudo python setup.py install
    
  4. Test the installation:

    python examples/example.py
    

PyPI

The Python package manager, pip, is required to install the API from PyPI.

  1. Install the API:

    pip install gpudb --upgrade
    
  2. Test the installation:

    python -c "import gpudb;print('Import Successful')"
    

    If Import Successful is displayed, the API has been installed as is ready for use.

Data File

The example script makes reference to a nyc_neighborhood.csv data file in the current directory. This can be updated to point to a valid path on the host where the file will be located, or the script can be run with the data file in the current directory.

CSV = "nyc_neighborhood.csv"

Script Detail

This example is going to demonstrate solving for the quickest route between a given set of taxi trip endpoints. The trips are composed of a pickup and dropoff point, with each trip weighted based on how expensive it was.

Constants

Several constants are defined at the beginning of the script:

  • HOST / PORT -- host and port values for the database
  • OPTION_NO_ERROR -- reference to a /clear/table option for ease of use and repeatability
  • TABLE_NYC_N -- the name of the table into which the NYC Neighborhood dataset is loaded. This dataset is joined to the TABLE_TAXI table to create the JOIN_TAXI dataset.
  • TABLE_TAXI -- the name of the table into which the NYC taxi dataset is loaded. This dataset is joined to the TABLE_NYC_N table to create the JOIN_TAXI dataset.
  • TABLE_TAXI_EW -- the name of the projection derived from the JOIN_TAXI dataset that serves as the base dataset for the GRAPH_T graph.
  • JOIN_TAXI -- the name of the join view that represents the dataset of all the trips found in the TABLE_TAXI dataset that overlap with the neighborhood boundaries found in the TABLE_NYC_N dataset
  • GRAPH_T -- the NYC taxi graph
  • GRAPH_T_MRSOLVED -- the solved NYC taxi graph using the MULTIPLE_ROUTING solver type
HOST = "127.0.0.1"
PORT = "9191"

OPTION_NO_ERROR = {"no_error_if_not_exists": "true"}

TABLE_NYC_N = "nyc_neighborhood"
TABLE_TAXI = "nyctaxi"
TABLE_TAXI_EW = TABLE_TAXI + "_edges_weights_wkt"

JOIN_TAXI = "taxi_tables_joined"

GRAPH_T = TABLE_TAXI + "_graph_wkt"
GRAPH_T_MRSOLVED = GRAPH_T + "_multiple_routing_solved"

Graph Creation

One graph is used for this example: nyctaxi_graph_wkt, a graph utilizing WKT based on a modified version of the standard NYC Taxi dataset included with Kinetica installations.

To filter out data that could skew graph nyctaxi_graph_wkt, the NYC Neighborhood dataset must be inserted into Kinetica and joined to the NYC Taxi dataset using STXY_CONTAINS to remove any trip points in the NYC Taxi dataset that are not contained within the geospatial boundaries of the NYC Neighborhood dataset:

print(
    "Joining {} to {} to filter out data that could skew the taxi "
    "graphs.".format(TABLE_TAXI, JOIN_TAXI)
)
join_taxi_tables_response = kinetica.create_join_table(
    join_table_name=JOIN_TAXI,
    table_names=[TABLE_TAXI + " as t", TABLE_NYC_N + " as n"],
    column_names=[
        "CONCAT(CHAR32(pickup_longitude), CHAR32(pickup_latitude)) as pickup_name",
        "t.pickup_longitude", 
        "t.pickup_latitude",
        "HASH(t.pickup_longitude + t.pickup_latitude) as pickup_id",
        "CONCAT(CHAR32(dropoff_longitude), CHAR32(dropoff_latitude)) as dropoff_name",
        "t.dropoff_longitude", 
        "t.dropoff_latitude",
        "HASH(t.dropoff_longitude + t.dropoff_latitude) as dropoff_id",
        "t.total_amount"
    ],
    expressions=[
        "(STXY_CONTAINS(n.geom, t.pickup_longitude, t.pickup_latitude)) AND"
        "(STXY_CONTAINS(n.geom, t.dropoff_longitude, t.dropoff_latitude)) "
    ]
)["status_info"]["status"]

Before nyctaxi_graph_wkt can be created, the edges must be derived from the taxi_tables_joined dataset's XY pickup and dropoff pairs to create the nyctaxi_edges_weights_wkt dataset; note that REMOVE_NULLABLE is used to remove a nullable column property, which would prevent the graph from being created:

print(
    "Creating a projection from {} to contain the {} edges.".format(
        JOIN_TAXI, GRAPH_T
    )
)
edges_wkt_response = kinetica.create_projection(
    table_name=JOIN_TAXI,
    projection_name=TABLE_TAXI_EW,
    column_names=[
        "REMOVE_NULLABLE(ST_MAKELINE(ST_MAKEPOINT(pickup_longitude, pickup_latitude), ST_MAKEPOINT(dropoff_longitude, dropoff_latitude))) AS tripwkt",
        "total_amount"
    ],
    options={}
)["status_info"]["status"]

Now, nyctaxi_graph_wkt is created with the following characteristics:

  • It is not directed because the trips aren't in a meaningful order
  • It has no explicitly defined nodes because the example relies on the implicit nodes attached to the defined edges
  • The edges in this graph are represented using the WKT LINESTRINGs in the tripwkt column of the nyctaxi_edges_weights_wkt table (EDGE_WKTLINE).
  • The weights in this graph are represented using the dollar amounts found in the total_amount column of the nyctaxi_edges_weights_wkt table (WEIGHTS_VALUESPECIFIED). The weights are matched to the edges using the same tripwkt column as the edges (WEIGHTS_EDGE_WKTLINE).
  • It has no inherent restrictions for any of the nodes or edges in the graph
  • It will be replaced with this instance of the graph if a graph of the same name exists (recreate).
  • If nodes are within 0.01 degrees of each other, they will be merged together (merge_tolerance)
print("Creating {}".format(GRAPH_T))
create_t_graph_response = kinetica.create_graph(
    graph_name=GRAPH_T,
    directed_graph=False,
    nodes=[],
    edges=[
        TABLE_TAXI_EW + ".tripwkt AS EDGE_WKTLINE"
    ],
    weights=[
        TABLE_TAXI_EW + ".tripwkt AS WEIGHTS_EDGE_WKTLINE",
        TABLE_TAXI_EW + ".total_amount AS WEIGHTS_VALUESPECIFIED"
    ],
    restrictions=[],
    options={
        "recreate": "true",
        "merge_tolerance": "0.01"
    }
)

Multiple Routing

Before the nyctaxi_graph_wkt graph is solved, the source node and destination nodes are defined.

source_node = "POINT(-73.98438262939453 40.76493835449219)"  # node 2
destination_nodes = [
    "POINT(-73.97122955322266 40.74700927734375)",  # node 39
    "POINT(-73.97740173339844 40.77263641357422)"  # node 85
]

Next, the graph is solved with the solve results being exported to the response:

solve_t1_mrgraph_response = kinetica.solve_graph(
    graph_name=GRAPH_T,
    solver_type="MULTIPLE_ROUTING",
    source_nodes=[source_node], 
    destination_nodes=destination_nodes,
    solution_table=GRAPH_T_MRSOLVED,
    options={"export_solve_results": "true"}
)["result_per_destination_node"][0]

The cost for the source node to visit the destination nodes is represented as total amount in dollars:

Cost for source node POINT(-73.98438262939453 40.76493835449219) to visit destination nodes ['POINT(-73.97122955322266 40.74700927734375)', 'POINT(-73.97740173339844 40.77263641357422)']: $218.46

The solution output to WMS:

../../_images/nyctaxi_mr_solved.png

Download & Run

Included below is a complete example containing all the above requests, the data files, and output.

To run the complete sample, ensure the solve_graph_nyctaxi_multi_route.py and nyc_neighborhood.csv files are in the same directory (assuming the locations were not changed in the solve_graph_nyctaxi_multi_route.py script) and the nyctaxi dataset has been ingested; then switch to that directory and do the following:

  • If on the Kinetica host:

    /opt/gpudb/bin/gpudb_python solve_graph_nyctaxi_multi_route.py
    
  • If running after using PyPI or GitHub to install the Python API:

    python solve_graph_nyctaxi_multi_route.py