partial cython-linting in graphs/

src/sage/graphs/base/boost_graph.pyx

@@ -1183,7 +1183,6 @@ cpdef johnson_shortest_paths(g, weight_function=None, distances=True, predecesso
     cdef BoostVecWeightedGraph g_boost_und
     cdef int N = g.num_verts()
     cdef vector[vector[double]] result
-    cdef int u_int, v_int
 
     if g.is_directed():
         boost_weighted_graph_from_sage_graph(&g_boost_dir, g, v_to_int, weight_function)
@@ -1340,7 +1339,6 @@ cpdef floyd_warshall_shortest_paths(g, weight_function=None, distances=True, pre
     cdef BoostVecWeightedGraph g_boost_und
     cdef int N = g.num_verts()
     cdef vector[vector[double]] result
-    cdef int u_int, v_int
 
     if g.is_directed():
         boost_weighted_graph_from_sage_graph(&g_boost_dir, g, v_to_int, weight_function)
@@ -2330,13 +2328,13 @@ cdef double diameter_DiFUB(BoostVecWeightedDiGraphU g_boost,
     import sys
     # These variables are automatically deleted when the function terminates.
     cdef double LB, LB_1, LB_2, UB
-    cdef v_index s, m, d, v, tmp
+    cdef v_index m, v, tmp
     cdef v_index i
     cdef vector[double] distances
     cdef vector[pair[double, v_index]] order_1, order_2
 
     # We select a vertex with low eccentricity using 2Dsweep
-    LB, s, m, d = diameter_lower_bound_2Dsweep(g_boost, rev_g_boost,
+    LB, _, m, _ = diameter_lower_bound_2Dsweep(g_boost, rev_g_boost,
                                                source, algorithm)
 
     # If the lower bound is a very large number, it means that the digraph is
@@ -2969,7 +2967,6 @@ cpdef wiener_index(g, algorithm=None, weight_function=None, check_weight=True):
 
     # These variables are automatically deleted when the function terminates.
     cdef v_index vi, u, v
-    cdef dict int_to_v = dict(enumerate(g))
     cdef dict v_to_int = {vv: vi for vi, vv in enumerate(g)}
     cdef BoostVecWeightedDiGraphU g_boost_dir
     cdef BoostVecWeightedGraph g_boost_und

src/sage/graphs/base/c_graph.pyx

@@ -44,7 +44,7 @@ method :meth:`realloc <sage.graphs.base.c_graph.CGraph.realloc>`.
 # ****************************************************************************
 
 from sage.data_structures.bitset_base cimport *
-from sage.rings.integer cimport Integer, smallInteger
+from sage.rings.integer cimport smallInteger
 from sage.arith.long cimport pyobject_to_long
 from libcpp.queue cimport priority_queue, queue
 from libcpp.stack cimport stack
@@ -3751,7 +3751,6 @@ cdef class CGraphBackend(GenericGraphBackend):
         # studied.
         cdef int x_int = self.get_vertex(x)
         cdef int y_int = self.get_vertex(y)
-        cdef int u = 0
         cdef int v = 0
         cdef int w = 0
         cdef int pred
@@ -3978,7 +3977,6 @@ cdef class CGraphBackend(GenericGraphBackend):
         # studied.
         cdef int x_int = self.get_vertex(x)
         cdef int y_int = self.get_vertex(y)
-        cdef int u = 0
         cdef int v = 0
         cdef int w = 0
         cdef int pred
@@ -4680,7 +4678,6 @@ cdef class CGraphBackend(GenericGraphBackend):
                         # // answer = [u]
                         cycle = [self.vertex_label(u)]
 
-                        tmp = u
                         while u != uu:
                             u = parent.get(u, uu)
                             cycle.append(self.vertex_label(u))
@@ -4899,7 +4896,7 @@ cdef class Search_iterator:
             sage: next(g.breadth_first_search(0))
             0
         """
-        cdef int v_int, v_dist
+        cdef int v_int
         cdef int w_int
         cdef int l
         cdef CGraph cg = self.graph.cg()

src/sage/graphs/base/dense_graph.pyx

@@ -236,17 +236,15 @@ cdef class DenseGraph(CGraph):
             sage: D.realloc(30)
             sage: D.current_allocation()
             30
-
         """
-        cdef int i, j
+        cdef int i
         if not total_verts:
             raise RuntimeError('dense graphs must allocate space for vertices')
 
         cdef bitset_t bits
-        cdef int min_verts, min_longs
+        cdef int min_verts
         if <size_t>total_verts < self.active_vertices.size:
             min_verts = total_verts
-            min_longs = -1
             bitset_init(bits, self.active_vertices.size)
             bitset_set_first_n(bits, total_verts)
             if not bitset_issubset(self.active_vertices, bits):
@@ -402,7 +400,7 @@ cdef class DenseGraph(CGraph):
         """
         cdef int num_arcs_old = self.num_arcs
 
-        cdef size_t i, j
+        cdef size_t i
         i = bitset_next(self.active_vertices, 0)
         while i != -1:
             self.add_arc_unsafe(i, i)

src/sage/graphs/base/graph_backends.pyx

@@ -47,7 +47,6 @@ For an overview of graph data structures in sage, see
 Classes and methods
 -------------------
 """
-
 # ****************************************************************************
 #       Copyright (C) 2008 Robert L. Miller <rlmillster@gmail.com>
 #                     2018 Julian Rüth <julian.rueth@fsfe.org>
@@ -58,8 +57,7 @@ Classes and methods
 # (at your option) any later version.
 #                  https://www.gnu.org/licenses/
 # ****************************************************************************
-
-from .c_graph cimport CGraphBackend, CGraph
+from .c_graph cimport CGraphBackend
 
 
 cdef class GenericGraphBackend(SageObject):

src/sage/graphs/base/sparse_graph.pxd

@@ -1,12 +1,12 @@
-#*****************************************************************************
+# ****************************************************************************
 #       Copyright (C) 2008-2009 Robert L. Miller <rlmillster@gmail.com>
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
 # the Free Software Foundation, either version 2 of the License, or
 # (at your option) any later version.
-#                  http://www.gnu.org/licenses/
-#*****************************************************************************
+#                  https://www.gnu.org/licenses/
+# ****************************************************************************
 
 from .c_graph cimport CGraph, CGraphBackend
 cimport cython
@@ -23,6 +23,7 @@ cdef struct SparseGraphBTNode:
     SparseGraphBTNode *left
     SparseGraphBTNode *right
 
+
 @cython.final
 cdef class SparseGraph(CGraph):
     cdef int hash_length

src/sage/graphs/base/sparse_graph.pyx

@@ -1009,10 +1009,9 @@ cdef class SparseGraph(CGraph):
 
         - a pointer to the first label or ``NULL`` if there are none
         """
-        cdef int i = (u * self.hash_length) + (v & self.hash_mask), j
-        cdef int compared, num_arcs
+        cdef int i = (u * self.hash_length) + (v & self.hash_mask)
+        cdef int compared
         cdef SparseGraphBTNode *temp = self.vertices[i]
-        cdef SparseGraphLLNode *label
         while temp:
             compared = compare(temp.vertex, v)
             if compared > 0:

src/sage/graphs/base/static_dense_graph.pyx

@@ -216,7 +216,7 @@ def is_strongly_regular(g, parameters=False):
     cdef bitset_t b_tmp
     cdef int n = g.order()
     cdef int inter
-    cdef int i, j, l, k
+    cdef int i, j, k
 
     if not g.order() or not g.size():  # no vertices or no edges
         return False

src/sage/graphs/base/static_sparse_backend.pyx

@@ -684,7 +684,6 @@ cdef class StaticSparseBackend(CGraphBackend):
             raise LookupError("one of the two vertices does not belong to the graph")
 
         cdef StaticSparseCGraph cg = self._cg
-        cdef list l
 
         cdef uint32_t * edge = has_edge(cg.g, u, v)
         if not edge:
@@ -696,9 +695,7 @@ cdef class StaticSparseBackend(CGraphBackend):
         # all labels.
         if self.multiple_edges(None):
             return self._all_edge_labels(u, v, edge)
-
-        else:
-            return edge_label(cg.g, edge)
+        return edge_label(cg.g, edge)
 
     cdef inline list _all_edge_labels(self, int u, int v, uint32_t* edge=NULL):
         """
@@ -1079,7 +1076,7 @@ cdef class StaticSparseBackend(CGraphBackend):
           - ``2`` -- as ``1`` but ignore the labels
         """
         cdef object v, l
-        cdef int u_int, prev_u_int, v_int, l_int, l_int_other, tmp
+        cdef int u_int, prev_u_int, v_int, l_int_other, tmp
         cdef StaticSparseCGraph cg = self._cg
         cdef CGraph cg_other = other.cg()
         cdef list b_vertices_2

src/sage/graphs/base/static_sparse_graph.pxd

@@ -8,17 +8,17 @@ ctypedef unsigned int uint
 cdef extern from "stdlib.h":
     ctypedef void const_void "const void"
     void qsort(void *base, int nmemb, int size,
-            int(*compar)(const_void *, const_void *)) nogil
+               int(*compar)(const_void *, const_void *)) nogil
 
     void *bsearch(const_void *key, const_void *base, size_t nmemb,
                   size_t size, int(*compar)(const_void *, const_void *)) nogil
 
 ctypedef struct short_digraph_s:
-   uint32_t *  edges
-   uint32_t ** neighbors
-   PyObject * edge_labels
-   int m
-   int n
+    uint32_t *  edges
+    uint32_t ** neighbors
+    PyObject * edge_labels
+    int m
+    int n
 
 ctypedef short_digraph_s short_digraph[1]
 

src/sage/graphs/base/static_sparse_graph.pyx

@@ -182,7 +182,6 @@ with C arguments).
 # ****************************************************************************
 
 cimport cpython
-from libc.string cimport memset
 from libc.limits cimport INT_MAX
 from libc.math cimport sqrt
 from libcpp.vector cimport vector
@@ -783,7 +782,6 @@ cdef void strongly_connected_components_digraph_C(short_digraph g, int nscc, int
     cdef MemoryAllocator mem = MemoryAllocator()
     cdef size_t v, w, i
     cdef size_t s_nscc = <size_t>nscc
-    cdef int tmp = nscc + 1
     cdef vector[vector[int]] scc_list = vector[vector[int]](nscc, vector[int]())
     cdef vector[vector[int]] sons = vector[vector[int]](nscc + 1, vector[int]())
     cdef vector[int].iterator iter
@@ -827,7 +825,6 @@ cdef void strongly_connected_components_digraph_C(short_digraph g, int nscc, int
     output.neighbors[0] = output.edges
 
     for v in range(1, s_nscc + 1):
-        degv = sons[v].size()
         output.neighbors[v] = output.neighbors[v - 1] + sons[v - 1].size()
         for i in range(sons[v].size()):
             output.neighbors[v][i] = sons[v][i]

src/sage/graphs/generators/distance_regular.pyx

@@ -1277,7 +1277,6 @@ def graph_from_GQ_spread(const int s, const int t):
 
     (GQ, S) = designs.generalised_quadrangle_with_spread(s, t, check=False)
 
-    k = len(GQ.blocks()[0])
     edges = []
     for b in GQ.blocks():
         if b in S:  # skip blocks in spread
@@ -1286,8 +1285,7 @@ def graph_from_GQ_spread(const int s, const int t):
             sig_check()
             edges.append((p1, p2))
 
-    G = Graph(edges, format="list_of_edges")
-    return G
+    return Graph(edges, format="list_of_edges")
 
 
 def GeneralisedDodecagonGraph(const int s, const int t):
@@ -1763,17 +1761,14 @@ def _line_graph_generalised_polygon(H):
             sig_check()
             vToLines[p].append(l)
 
-    k = len(vToLines[lines[0][0]])
-
     edges = []
     for v in vToLines:
         lines = vToLines[v]
         for l1, l2 in itertools.combinations(lines, 2):
             sig_check()
             edges.append((l1, l2))
 
-    G = Graph(edges, format="list_of_edges")
-    return G
+    return Graph(edges, format="list_of_edges")
 
 
 def _intersection_array_from_graph(G):

src/sage/graphs/graph_decompositions/bandwidth.pyx

@@ -254,7 +254,7 @@ def bandwidth(G, k=None):
     cdef range_t ** ith_range_array = <range_t **> mem.allocarray(n, sizeof(range_t *))
     cdef range_t * range_array_tmp = <range_t *> mem.allocarray(n, sizeof(range_t))
 
-    cdef int i, j, kk
+    cdef int i, kk
     # compute the distance matrix
     all_pairs_shortest_path_BFS(G, NULL, distances, NULL, vertex_list=int_to_vertex)
 

src/sage/graphs/graph_decompositions/clique_separators.pyx

@@ -21,7 +21,6 @@ Methods
 #                  https://www.gnu.org/licenses/
 # ****************************************************************************
 
-from libcpp.pair cimport pair
 from libcpp.vector cimport vector
 from libc.stdint cimport uint32_t
 from cysignals.signals cimport sig_on, sig_off, sig_check
@@ -523,8 +522,6 @@ def atoms_and_clique_separators(G, tree=False, rooted_tree=False, separators=Fal
     cdef vector[int] Sint_min
     cdef vector[int] Cint
     cdef vector[int] Hx
-    cdef size_t ui, vi
-    cdef bint stop
 
     for i in range(N):
         sig_check()

src/sage/graphs/graph_decompositions/cutwidth.pyx

@@ -528,6 +528,7 @@ def cutwidth_dyn(G, lower_bound=0):
     finally:
         sig_free(neighborhoods)
 
+
 cdef inline int exists(FastDigraph g, uint8_t* neighborhoods, int S, int cost_S, int v, int k):
     r"""
     Check whether an ordering with the given cost `k` exists, and updates data
@@ -571,7 +572,6 @@ cdef inline int exists(FastDigraph g, uint8_t* neighborhoods, int S, int cost_S,
     cdef int mini = (<uint8_t> -1)
 
     cdef int i
-    cdef int next_set
 
     # For each possible extension of the current set with a vertex, check whether
     # there exists a cheap path toward {1..n}, and update the cost.
@@ -735,7 +735,7 @@ def cutwidth_MILP(G, lower_bound=0, solver=None, verbose=0,
 
     p.set_objective(z['z'])
 
-    obj = p.solve(log=verbose)
+    _ = p.solve(log=verbose)
 
     # We now extract the ordering and the cost of the solution
     val_x = p.get_values(x, convert=bool, tolerance=integrality_tolerance)

src/sage/graphs/graph_decompositions/fast_digraph.pxd

@@ -10,5 +10,3 @@ cdef int compute_out_neighborhood_cardinality(FastDigraph, int)
 
 cdef int popcount32(int)
 cdef int slow_popcount32(int)
-
-

src/sage/graphs/graph_decompositions/fast_digraph.pyx

@@ -12,10 +12,9 @@ cardinality).
 In the following code, sets are represented as integers, where the `i`-th bit is
 set if element `i` belongs to the set.
 """
-
-from libc.stdint cimport uint8_t
 from cysignals.memory cimport check_allocarray, check_calloc, sig_free
 
+
 cdef class FastDigraph:
 
     def __cinit__(self, D, vertex_list=None):
@@ -53,7 +52,7 @@ cdef class FastDigraph:
         self.n = D.order()
         self.graph = <int *>check_calloc(self.n, sizeof(int))
 
-        cdef int i, j
+        cdef int i
         cdef int tmp
 
         # When the vertices are not consecutive integers

src/sage/graphs/graph_decompositions/graph_products.pyx

@@ -130,8 +130,6 @@ Methods
 #                  https://www.gnu.org/licenses/
 # ****************************************************************************
 
-from copy import copy
-
 
 def is_cartesian_product(g, certificate=False, relabeling=False):
     r"""

src/sage/graphs/graph_decompositions/rankwidth.pxd

@@ -10,6 +10,3 @@ cdef extern from "rw.h":
     subset_t *adjacency_matrix
 
 cdef void print_rank_dec(subset_t s, int l)
-
-
-