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## [igraph] problems with large graphs

 From: Eytan Bakshy Subject: [igraph] problems with large graphs Date: Sat, 6 Sep 2008 15:01:33 -0400

```Hello,

```
I am using igraph 0.5.1 python and I am running into some difficulty various things with large graphs. I am using a Mac Pro with 18GB of RAM (not that I can generally address more than 3-4GB for any given 32- bit application, like igraph/python).
```

Erdos-Reyni graphs with many vertices
---

Constructing a random graph as follows works:
g = Graph.Erdos_Renyi(n=249553,m=100000)
but when n is any larger, e.g.:
g = Graph.Erdos_Renyi(n=249554,m=100000)

I get the error:
ValueError: m must be between 0 and n^2

```
This seems to happen for various values of m between 0 and n^2 for any n > 249,553
```

Computing similarity measures for large graphs
---
```
I am running across out of memory errors and segfaults using similarity_inverse_log_weighted() in working with my dataset (~350k nodes, ~4.5m edges). For my graph and randomly generated graphs of this size, Jaccard and Dice seem to work just fine. Here is a reproducible example of my problem:
```

```
Generate a very sparse random graph with 20,000 nodes (problem also holds for denser graphs)
```        g = Graph.Erdos_Renyi(n=20000,m=400);
g.similarity_inverse_log_weighted([2000,6000])
gives me:
```
python2.5(34740) malloc: *** mmap(size=3200000000) failed (error code=12)
```        *** error: can't allocate region
*** set a breakpoint in malloc_error_break to debug

---------------------------------------------------------------------------
```
InternalError Traceback (most recent call last)
```
```
/Volumes/Data/projects/secondlife/septAnalysis/data/transactions/ <ipython console> in <module>()
```
InternalError: Error at cocitation.c:171: , Out of memory

```
For BA graphs with 300,000 nodes using the same measure, I get a segfault. Would it be possible to perform this computation using less memory?
```

Thanks,
-e

```