[GRASS-dev] Re: v.in.ogr [Re: [GRASS5] v.in.ascii]

GRASS GIS GRASS GIS developer
,
1

Helena,
(cc to grass-dev, private msg part removed)

it is definitely related to the topology, but I don't know
if *identical* to the v.in.ascii problem. I will try to test
that next week.

Maybe a list member has an idea?

Markus

On Fri, May 19, 2006 at 09:44:08AM -0400, Helena Mitasova wrote:

Markus,
is the v.in.ogr swaping problem related in any way to the v.in.ascii
problem (see my discussion with Radim below).
Would Radim's suggestions below help to solve it?

Helena

-------- Original Message --------
Subject: Re: [GRASS5] v.in.ascii
Date: Mon, 22 Aug 2005 11:08:42 +0200
From: Radim Blazek <radim.blazek@gmail.com>
To: Helena Mitasova <hmitaso@unity.ncsu.edu>
CC: grass5 developers list <grass5@grass.itc.it>
References: <20050801082802.GN8595@thuille.itc.it>
<20050802085033.GA27707@thuille.itc.it> <42F79F09.6080303@noaa.gov>
<42FA2976.2060704@unity.ncsu.edu>
<340505ef05081601295cad878b@mail.gmail.com> <430218B8.80604@unity.ncsu.edu>

On 8/16/05, Helena Mitasova <hmitaso@unity.ncsu.edu> wrote:
>Radim Blazek wrote:
>> Please read my previous mails about that, IT IS implemented,
>> and IT DOES NOT call free() by default because it is faster
>> and IT CAN free the memory if it is necessary. I wrote that 2-3
>> times already.
>
>I meant at the module level, as a user how can I tell v.in.ascii or
>v.build or any other module that builds topology to free the memory
>when needed? From your emails it seemed to me
>that this option needs to be added to the relevant modules, but I might
>have misunderstood it,
>
>Helena

Spatial index occupies a lot of memory but it is necessary for
topology building. Also, it takes long time to release the memory
occupied by spatial index (dig_spidx_free) .

The function building topology (Vect_build) is usually called
at the end of module (before Vect_close) so it is faster to call
exit() and operating system releases all the memory much faster.
By default the memory is not released.

It is possible to call Vect_set_release_support() before Vect_close()
to force to release the memory, but it takes long time on large files.

Currently most of the modules do not release spatial index and work
like this:
main
{
    Vect_open_new()
    //writing new vector

    Vect_build()
    Vect_close() // memory is not released
}

you can add Vect_set_release_support():

main
{
    Vect_open_new()
    // writing new vector

    Vect_build()
    Vect_set_release_support()
    Vect_close() // memory is released
}

but it only takes longer time.

It make sense to release spatial index if it is used only at the beginning
of a module or in permanently running programs like QGIS.
For example:

main
{
    Vect_open_old()
    // select features using spatial index, e.g. Vect_select_lines_by_box()
    Vect_set_release_support()
    Vect_close() // memory is released

    // do some processing which needs memory
}

Radim