Dear pgrouting dev team,

I am hitting a problem with the pgr_withPoints function family and

wanted to ask you for further guidance and/or advice on how to deal with

it.

First I would like to outline the task I am working on:

I am calculating an origin destination matrix for two sets of points

(eg. The start_points and end_points), so I am particularly interested

in retrieving the cost between each startpoint and endpoint using the

pgr_withPointsCost() function. As a cost factor I am normally using

precalculated time-costs (seconds) as cost and reverse_cost depicting

the (real) time a cyclist needs to traverse an edge (I will call those

costs real_cost). In order to model a cyclists route choice more

accurately I am introducing a multiplicator for costs on edges that seem

unpleasant to ride on. Costs on those edges get multiplied by 100 in

order to retrieve a more realistic routing output. As a result of this

extra modelling, the pgr_withPointsCost() function aggregates costs

based on the multiplied cost attributes and do not reflect the initial

time (eg. real_cost) along the path properly.

My approach to solve this problem would be to join and aggregate the

real time costs (which is stored in the input graph table) costs along

the manipulated routing output involves the use of pgr_withPoints()

function. In more detail: This function allows me to first store the

individual path elements of the routes in a result table. Then I would

like to join the real cost based on the edge attributes of the routing

output and the input graph table and group by start_pid and end_pid

while applying sum(real_cost).

But when changing the pgr_withPointsCost() function to pgr_withPoints()

function I repeatedly run into some heavy memory leakage (different

errors that seem to occur in the pgr_withPoints() function). I can give

you some details on the tests I did:

1) Testrun with create table as pgr_withPointsCost() using a graph

with ~50000 edges, ~4000 Start and End pids: completes without errors

(although 99% of memory is used).

2) Testrun with create table as pgr_withPoints() using a graph with

~50000 edges, ~4000 Start and End pids: ERROR std::bad_alloc Hint:

Working with directed Graph.

3) Testrun with create table as pgr_withPoints() using a graph with

~50000 edges, 100 Start and ~4000 End pids: ERROR invalid memory alloc

request size 3474796248 Where: SQL-Funktion »pgr_withpoints«

4) Testrun with create table as pgr_withPoints() using a graph with

~50000 edges, 10 Start and ~4000 End pids: completes without errors (50

sec)

I checked the whole issues history of pgrouting on github and found

tests with way more startpoints (around 80000, but also using

pgr_withPointsCost() and way more RAM) – maybe it is related:

https://github.com/pgRouting/pgrouting/issues/694#issuecomment-288035720Are you familiar with this kind of behaviour of pgr_withPoints(), which

ultimately calls just pgr_dijkstra()? Is this a memory leak or do I

just not have enough RAM (24GB)? Do you have any hints on how to solve

this issue or do you experience similar problems? I would like to avoid

cutting the query into smaller chuncs of start_points and iterate over

them as it is very time inefficient to run such queries.

I am currently running Postgresql Version 10.3, 64 bit, PostGIS v. 2.4

and pgrouting 2.6.0, release/2.6.1.59.0 on a Windows 10, 64bit Machine

with 24GB of RAM. I will also try updating a test system to the current

postgres, postgis and pgrouting versions and run the query again.

I would be glad if you could have a look into this.

Best regards,

Clemens

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