debian/changelog

+igraph (0.7.1-4) UNRELEASED; urgency=medium
+
+  * use a different starting vector for
+    igraph_community_leading_eigenvector() to prevent errors
+    with ARPACK 3.6.3 (Thanks for the patch to Tamás Nepusz)
+    Closes: #902760
+  * Drop Tamás Nepusz <ntamas@gmail.com> from uploaders (Tamás, thanks
+    for your previous work on the Debian package and the support you
+    provide on upstream code)
+  * debhelper 12
+  * Standards-Version: 4.3.0
+
+ -- Andreas Tille <tille@debian.org>  Thu, 10 Jan 2019 21:22:59 +0100
+
 igraph (0.7.1-3) unstable; urgency=medium
 
   [ Mathieu Malaterre ]

debian/compat

-11
+12

debian/control

 Source: igraph
 Maintainer: Debian Med Packaging Team <debian-med-packaging@lists.alioth.debian.org>
-Uploaders: Andreas Tille <tille@debian.org>,
-           Tamás Nepusz <ntamas@gmail.com>
+Uploaders: Andreas Tille <tille@debian.org>
 Section: libs
 Priority: optional
-Build-Depends: debhelper (>= 11~),
+Build-Depends: debhelper (>= 12~),
                libtool,
                libxml2-dev,
                libgmp-dev,
@@ -14,7 +13,7 @@ Build-Depends: debhelper (>= 11~),
                automake,
                libglpk-dev,
                libf2c2-dev
-Standards-Version: 4.2.1
+Standards-Version: 4.3.0
 Vcs-Browser: https://salsa.debian.org/med-team/igraph
 Vcs-Git: https://salsa.debian.org/med-team/igraph.git
 Homepage: http://igraph.org/c/

debian/patches/different_starting_vector.patch

+From: Tamas Nepusz <ntamas@gmail.com>
+Date: Wed, 2 Jan 2019 16:51:48 +0100
+Origin: https://github.com/igraph/igraph/commit/17cc5be8.patch
+Bug-Debian: https://bugs.debian.org/902760
+Bug-Upstream: https://github.com/igraph/igraph/issues/1107
+Subject: [PATCH] use a different starting vector for
+ igraph_community_leading_eigenvector() to prevent errors with ARPACK 3.6.3
+
+---
+ src/community.c | 15 +++++++++++----
+ 1 file changed, 11 insertions(+), 4 deletions(-)
+
+--- a/src/community.c
++++ b/src/community.c
+@@ -1736,13 +1736,19 @@ int igraph_community_leading_eigenvector
+       igraph_set_error_handler(errh);
+       igraph_set_warning_handler(warnh);
+       if (options->nconv < 1) {
+-	/* Call again, from a fixed starting point */
++	/* Call again from a fixed starting point. Note that we cannot use a
++	 * fixed all-1 starting vector as sometimes ARPACK would return a
++	 * 'starting vector is zero' error -- this is of course not true but
++	 * it's a result of ARPACK >= 3.6.3 trying to force the starting vector
++	 * into the range of OP (i.e. the matrix being solved). The initial
++	 * vector we use here seems to work, but I have no theoretical argument
++	 * for its usage; it just happens to work. */
+ 	options->start=1;
+ 	options->info=0;
+ 	options->ncv=0;
+ 	options->lworkl = 0;	/* we surely have enough space */
+ 	for (i=0; i < options->n ; i++) {
+-	  storage.resid[i] = 1;
++	  storage.resid[i] = i % 2 ? 1 : -1;
+ 	}
+ 	IGRAPH_CHECK(igraph_arpack_rssolve(arpcb2, &extra, options, &storage,
+ 					   /*values=*/ 0, /*vectors=*/ 0));
+@@ -1774,12 +1780,13 @@ int igraph_community_leading_eigenvector
+ 			    /*values=*/ 0, /*vectors=*/ 0);
+       igraph_set_error_handler(errh);
+       if (options->nconv < 1) {
+-	/* Call again from a fixed starting point */
++	/* Call again from a fixed starting point. See the comment a few lines
++	 * above about the exact choice of this starting vector */
+ 	options->start=1;
+ 	options->info=0;
+ 	options->ncv=0;
+ 	options->lworkl = 0;	/* we surely have enough space */
+-	for (i=0; i < options->n; i++) { storage.resid[i] = 1; }
++	for (i=0; i < options->n; i++) { storage.resid[i] = i % 2 ? 1 : -1; }
+ 	IGRAPH_CHECK(igraph_arpack_rssolve(arpcb1, &extra, options, &storage, 
+ 					   /*values=*/ 0, /*vectors=*/ 0));
+ 	options->start=0;

debian/patches/series

@@ -5,3 +5,4 @@ drl_spelling_fix.patch
 skip_tests_accessing_remote.patch
 fix_test_arpack-3.6.patch
 fix_broken_graph_ml.patch
+different_starting_vector.patch

debian/rules

@@ -19,7 +19,7 @@ CONF_FLAGS=\
 override_dh_auto_configure:
 	dh_auto_configure -- $(CONF_FLAGS)
 
-override_dh_auto_test:
-ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
-	dh_auto_test || true
-endif
+#override_dh_auto_test:
+#ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
+#	dh_auto_test || true
+#endif