| // Copyright ©2014 The gonum Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| // Package simple provides a suite of simple graph implementations satisfying |
| // the gonum/graph interfaces. |
| package simple // import "gonum.org/v1/gonum/graph/simple" |
| |
| import ( |
| "math" |
| |
| "gonum.org/v1/gonum/graph" |
| "gonum.org/v1/gonum/graph/internal/set" |
| ) |
| |
| // Node is a simple graph node. |
| type Node int64 |
| |
| // ID returns the ID number of the node. |
| func (n Node) ID() int64 { |
| return int64(n) |
| } |
| |
| // Edge is a simple graph edge. |
| type Edge struct { |
| F, T graph.Node |
| W float64 |
| } |
| |
| // From returns the from-node of the edge. |
| func (e Edge) From() graph.Node { return e.F } |
| |
| // To returns the to-node of the edge. |
| func (e Edge) To() graph.Node { return e.T } |
| |
| // Weight returns the weight of the edge. |
| func (e Edge) Weight() float64 { return e.W } |
| |
| // isSame returns whether two float64 values are the same where NaN values |
| // are equalable. |
| func isSame(a, b float64) bool { |
| return a == b || (math.IsNaN(a) && math.IsNaN(b)) |
| } |
| |
| // maxInt is the maximum value of int64. |
| const maxInt = int64(^uint64(0) >> 1) |
| |
| // idSet implements available ID storage. |
| type idSet struct { |
| maxID int64 |
| used, free set.Int64s |
| } |
| |
| // newIDSet returns a new idSet. The returned value should not be passed |
| // except by pointer. |
| func newIDSet() idSet { |
| return idSet{maxID: -1, used: make(set.Int64s), free: make(set.Int64s)} |
| } |
| |
| // newID returns a new unique ID. The ID returned is not considered used |
| // until passed in a call to use. |
| func (s *idSet) newID() int64 { |
| for id := range s.free { |
| return id |
| } |
| if s.maxID != maxInt { |
| return s.maxID + 1 |
| } |
| for id := int64(0); id <= s.maxID+1; id++ { |
| if !s.used.Has(id) { |
| return id |
| } |
| } |
| panic("unreachable") |
| } |
| |
| // use adds the id to the used IDs in the idSet. |
| func (s *idSet) use(id int64) { |
| s.used.Add(id) |
| s.free.Remove(id) |
| if id > s.maxID { |
| s.maxID = id |
| } |
| } |
| |
| // free frees the id for reuse. |
| func (s *idSet) release(id int64) { |
| s.free.Add(id) |
| s.used.Remove(id) |
| } |