Crash in sample_correlated_gnp

[youngser]

Hello,

The following sequence causes R crashed on me on mac and linux:

igraph.version()
[1] "1.0.0"

library(igraph)
set.seed(123)
B <- cbind( c(.2, .1), c(.1, .3) )
g <- sample_sbm(1000, pref.matrix=B, block.sizes=c(300,700))
g2 <- sample_correlated_gnp(g, corr = 0.5)

[gaborcsardi]

Yes, unfortunately. :(

[youngser]

Is this still in your todo list?
If so,is it possible if you can move it up?
Thanks!

[gaborcsardi]

Here is a stack

* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0xfffffffd00f15db0)
  * frame #0: 0x0000000108124f83 igraph.so`igraph_correlated_game(old_graph=<unavailable>, new_graph=0x00007ffeefbfd120, corr=0, p=498799, permutation=0x0000000000000000) at games.c:0:24 [opt]
    frame #1: 0x00000001082496ec igraph.so`R_igraph_correlated_game(old_graph=<unavailable>, corr=<unavailable>, p=<unavailable>, permutation=0x0000000101002ee0) at rinterface.c:10195:3 [opt]
    frame #2: 0x000000010015865b libR.dylib`R_doDotCall(ofun=<unavailable>, nargs=<unavailable>, cargs=0x00007ffeefbfda00, call=0x00000001091ca628) at dotcode.c:607:17 [opt]
    frame #3: 0x00000001001a451a libR.dylib`bcEval(body=0x00000001091cd850, rho=0x00000001091cbee0, useCache=<unavailable>) at eval.c:7659:21 [opt]
    frame #4: 0x000000010018a261 libR.dylib`Rf_eval(e=<unavailable>, rho=<unavailable>) at eval.c:727:8 [opt]
    frame #5: 0x00000001001aa791 libR.dylib`R_execClosure(call=0x00000001091cf770, newrho=<unavailable>, sysparent=<unavailable>, rho=0x0000000101040e08, arglist=<unavailable>, op=<unavailable>) at eval.c:0 [opt]
    frame #6: 0x00000001001a9569 libR.dylib`Rf_applyClosure(call=0x00000001091cf770, op=0x00000001091cfaf0, arglist=0x00000001091cbd58, rho=0x0000000101040e08, suppliedvars=0x0000000101002ee0) at eval.c:1818:16 [opt]
    frame #7: 0x000000010018a736 libR.dylib`Rf_eval(e=0x00000001091cf770, rho=0x0000000101040e08) at eval.c:850:12 [opt]
    frame #8: 0x00000001001adfbd libR.dylib`do_set(call=<unavailable>, op=0x0000000101001078, args=0x00000001091cf7e0, rho=0x0000000101040e08) at eval.c:2960:8 [opt]
    frame #9: 0x000000010018a459 libR.dylib`Rf_eval(e=0x00000001091cf850, rho=0x0000000101040e08) at eval.c:802:12 [opt]
    frame #10: 0x00000001001dfcea libR.dylib`Rf_ReplIteration(rho=0x0000000101040e08, savestack=<unavailable>, browselevel=0, state=0x00007ffeefbfe5c0) at main.c:264:2 [opt]
    frame #11: 0x00000001001e120f libR.dylib`run_Rmainloop [inlined] R_ReplConsole(rho=0x0000000101040e08, savestack=0, browselevel=0) at main.c:314:11 [opt]
    frame #12: 0x00000001001e11a6 libR.dylib`run_Rmainloop at main.c:1113 [opt]
    frame #13: 0x0000000100000f5b R`main + 27
    frame #14: 0x00007fff7c7e13d5 libdyld.dylib`start + 1

[szhorvat]

Thanks @gaborcsardi!

[szhorvat]

@gaborcsardi I think this is a bug in the R interface. The default value of the p parameter is old.graph$p, but that does not necessarily exist. When it is NULL, then a bad value is passed to the C function. I don't have a good enough understanding of how parameters as passed form R to C, but numeric(0) (which NULL becomes here) doesn't look like a valid value.

[melprice]

Has this been resolved yet or is there a work around? I am having the same issue. Thanks!

[szhorvat]

I think there are two issues here:

• One is that the R interface does not check that scalar arguments are indeed scalar. Instead, it just indexes them, and takes the first element. If the argument is zero-length, this causes a crash. This should be fixed in stimulus, in how it generates code. Perhaps we can add a check for the vector length. I have actually experimented with this very briefly @ntamas, but I'm too slow with R and can't afford the time now.
• Trying to take old.graph$p as mentioned in my comment above.

[ntamas]

I tried explicitly supplying p=edge_density(g) to sample_correlated_gnp(), but then it crashes with a different error so I'll have to investigate this more thoroughly tomorrow.

[szhorvat]

I don't get a crash, but a hang. I am about to add at least interruption support to igraph_correlated_game() on the master branch (will push soon).

[szhorvat]

Opened a C core issue igraph/igraph#2004

[szhorvat]

The issue on the C side is now fixed. The easiest immediate fix for the R-side issue is probably to use p=edge_density(g) by default.

[ntamas]

The issue is now also fixed in the development branch of the R interface. The fix will officially be released in R-igraph 1.3.0.