Re: [igraph] Igraph-python load bug?

[Tamas Nepusz]

Hi,

> If I change ‘tmp’ to have the following lines:
> 1234567890 123456120
> 12345 23457
> then the igraph.load command is VERY slow and basically hangs my  
> terminal.
The thing is that if you treat this file as an edge list, then igraph  
assumes that vertices are indexed from zero. Whenever it sees an ID  
like "1234567890" in the first, it immediately creates 1234567890  
other vertices, assuming that if there's a vertex with ID 1234567890,  
then there must be ones all the way from ID=0 up to ID=1234567889.

The solution is to use the NCOL format which is practically equivalent  
to an edge list as long as you have only two IDs (the source and the  
target) in a line. The good thing is that NCOL treats IDs as symbolic  
names and reassigns them to continuous IDs from zero, storing the  
"real" IDs in an attribute called "name".

For more info:
http://cneurocvs.rmki.kfki.hu/igraph/doc/python/igraph.GraphBase-class.html#Read_Ncol
http://bioinformatics.icmb.utexas.edu/lgl/

--
Tamas