write_graphml rounds float values to 4 decimal digits

[rajanski]

node in gml_file:

node
[
id 822
lat 52.5857663
lon 13.4500575
label "278215038"
]

same node in graphml_file (written after being read in though read_GML)

52.5858 13.4501 822 None 278215038

[rajanski]

tried write_dot, this doesnt round the values..

[ntamas]

Cannot reproduce on my machne; tried with the following test program:

#!/usr/bin/env python

from igraph import Graph, load

g = Graph(1)
g.vs["lat"] = 52.5857663
g.vs["lon"] = 13.4500575
g.write_gml("test.gml")
g2=load("test.gml")
g2.write_graphml("test.graphml")

It works just fine for me. The GraphML writer uses igraph_real_fprintf_precise from types.c in the C layer to ensure that floating-point values are written with the highest possible precision. It could be the case that this function does not work correctly due to some platform-dependent behaviour, but then I would need to know which platform you are working with.

[rajanski]

Hi Tamas, I am on Ubuntu 14.04 LTS 64 bit

[ntamas]

Did you compile the Python interface of igraph on your own or did you install it from a .deb package (via the package manager)? If so, where did you get the package from and which version of the Python interface are you using? (Try printing igraph.__version__ from Python).

[rajanski]

Hi, I installed igraph via pip. The interface version is 0.7.1

[ntamas]

I'll try to install it soon in a virtual machine and test it.

[ntamas]

Managed to confirm this in an Ubuntu 14.04 VM when installing igraph via pip without pre-installing the C core. Will investigate further.

[ntamas]

Okay, it turns out that this has been fixed already in the C core of igraph, but there was no new version released from the C core since the fix.

The commit in the source code of the C core is here: igraph/igraph@fdcaa14 .

[ntamas]

Related issue: igraph/igraph#796

[ntamas]

A workaround for the time being is to convert the floating-point attributes of your graph to strings before you save them, and then convert them back after loading. We'll have to wait until the next bugfix release of the C core to fix this properly.