// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2010 Gael Guennebaud <gael.guennebaud@inria.fr>
/*
NOTE: this routine has been adapted from the CSparse library:
Copyright (c) 2006, Timothy A. Davis.
http://www.suitesparse.com
CSparse is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
CSparse is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this Module; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "../Core/util/NonMPL2.h"
#ifndef EIGEN_SPARSE_AMD_H
#define EIGEN_SPARSE_AMD_H
namespace Eigen {
namespace internal {
template<typename T> inline T amd_flip(const T& i) { return -i-2; }
template<typename T> inline T amd_unflip(const T& i) { return i<0 ? amd_flip(i) : i; }
template<typename T0, typename T1> inline bool amd_marked(const T0* w, const T1& j) { return w[j]<0; }
template<typename T0, typename T1> inline void amd_mark(const T0* w, const T1& j) { return w[j] = amd_flip(w[j]); }
/* clear w */
template<typename StorageIndex>
static StorageIndex cs_wclear (StorageIndex mark, StorageIndex lemax, StorageIndex *w, StorageIndex n)
{
StorageIndex k;
if(mark < 2 || (mark + lemax < 0))
{
for(k = 0; k < n; k++)
if(w[k] != 0)
w[k] = 1;
mark = 2;
}
return (mark); /* at this point, w[0..n-1] < mark holds */
}
/* depth-first search and postorder of a tree rooted at node j */
template<typename StorageIndex>
StorageIndex cs_tdfs(StorageIndex j, StorageIndex k, StorageIndex *head, const StorageIndex *next, StorageIndex *post, StorageIndex *stack)
{
StorageIndex i, p, top = 0;
if(!head || !next || !post || !stack) return (-1); /* check inputs */
stack[0] = j; /* place j on the stack */
while (top >= 0) /* while (stack is not empty) */
{
p = stack[top]; /* p = top of stack */
i = head[p]; /* i = youngest child of p */
if(i == -1)
{
top--; /* p has no unordered children left */
post[k++] = p; /* node p is the kth postordered node */
}
else
{
head[p] = next[i]; /* remove i from children of p */
stack[++top] = i; /* start dfs on child node i */
}
}
return k;
}
/** \internal
* \ingroup OrderingMethods_Module
* Approximate minimum degree ordering algorithm.
*
* \param[in] C the input selfadjoint matrix stored in compressed column major format.
* \param[out] perm the permutation P reducing the fill-in of the input matrix \a C
*
* Note that the input matrix \a C must be complete, that is both the upper and lower parts have to be stored, as well as the diagonal entries.
* On exit the values of C are destroyed */
template<typename Scalar, typename StorageIndex>
void minimum_degree_ordering(SparseMatrix<Scalar,ColMajor,StorageIndex>& C, PermutationMatrix<Dynamic,Dynamic,StorageIndex>& perm)
{
using std::sqrt;
StorageIndex d, dk, dext, lemax = 0, e, elenk, eln, i, j, k, k1,
k2, k3, jlast, ln, dense, nzmax, mindeg = 0, nvi, nvj, nvk, mark, wnvi,
ok, nel = 0, p, p1, p2, p3, p4, pj, pk, pk1, pk2, pn, q, t, h;
StorageIndex n = StorageIndex(C.cols());
dense = std::max<StorageIndex> (16, StorageIndex(10 * sqrt(double(n)))); /* find dense threshold */
dense = (std::min)(n-2, dense);
StorageIndex cnz = StorageIndex(C.nonZeros());
perm.resize(n+1);
t = cnz + cnz/5 + 2*n; /* add elbow room to C */
C.resizeNonZeros(t);
// get workspace
ei_declare_aligned_stack_constructed_variable(StorageIndex,W,8*(n+1),0);
StorageIndex* len = W;
StorageIndex* nv = W + (n+1);
StorageIndex* next = W + 2*(n+1);
StorageIndex* head = W + 3*(n+1);
StorageIndex* elen = W + 4*(n+1);
StorageIndex* degree = W + 5*(n+1);
StorageIndex* w = W + 6*(n+1);
StorageIndex* hhead = W + 7*(n+1);
StorageIndex* last = perm.indices().data(); /* use P as workspace for last */
/* --- Initialize quotient graph ---------------------------------------- */
StorageIndex* Cp = C.outerIndexPtr();
StorageIndex* Ci = C.innerIndexPtr();
for(k = 0; k < n; k++)
len[k] = Cp[k+1] - Cp[k];
len[n] = 0;
nzmax = t;
for(i = 0; i <= n; i++)
{
head[i] = -1; // degree list i is empty
last[i] = -1;
next[i] = -1;
hhead[i] = -1; // hash list i is empty
nv[i] = 1; // node i is just one node
w[i] = 1; // node i is alive
elen[i] = 0; // Ek of node i is empty
degree[i] = len[i]; // degree of node i
}
mark = internal::cs_wclear<StorageIndex>(0, 0, w, n); /* clear w */
/* --- Initialize degree lists ------------------------------------------ */
for(i = 0; i < n; i++)
{
bool has_diag = false;
for(p = Cp[i]; p<Cp[i+1]; ++p)
if(Ci[p]==i)
{
has_diag = true;
break;
}
d = degree[i];
if(d == 1 && has_diag) /* node i is empty */
{
elen[i] = -2; /* element i is dead */
nel++;
Cp[i] = -1; /* i is a root of assembly tree */
w[i] = 0;
}
else if(d > dense || !has_diag) /* node i is dense or has no structural diagonal element */
{
nv[i] = 0; /* absorb i into element n */
elen[i] = -1; /* node i is dead */
nel++;
Cp[i] = amd_flip (n);
nv[n]++;
}
else
{
if(head[d] != -1) last[head[d]] = i;
next[i] = head[d]; /* put node i in degree list d */
head[d] = i;
}
}
elen[n] = -2; /* n is a dead element */
Cp[n] = -1; /* n is a root of assembly tree */
w[n] = 0; /* n is a dead element */
while (nel < n) /* while (selecting pivots) do */
{
/* --- Select node of minimum approximate degree -------------------- */
for(k = -1; mindeg < n && (k = head[mindeg]) == -1; mindeg++) {}
if(next[k] != -1) last[next[k]] = -1;
head[mindeg] = next[k]; /* remove k from degree list */
elenk = elen[k]; /* elenk = |Ek| */
nvk = nv[k]; /* # of nodes k represents */
nel += nvk; /* nv[k] nodes of A eliminated */
/* --- Garbage collection ------------------------------------------- */
if(elenk > 0 && cnz + mindeg >= nzmax)
{
for(j = 0; j < n; j++)
{
if((p = Cp[j]) >= 0) /* j is a live node or element */
{
Cp[j] = Ci[p]; /* save first entry of object */
Ci[p] = amd_flip (j); /* first entry is now amd_flip(j) */
}
}
for(q = 0, p = 0; p < cnz; ) /* scan all of memory */
{
if((j = amd_flip (Ci[p++])) >= 0) /* found object j */
{
Ci[q] = Cp[j]; /* restore first entry of object */
Cp[j] = q++; /* new pointer to object j */
for(k3 = 0; k3 < len[j]-1; k3++) Ci[q++] = Ci[p++];
}
}
cnz = q; /* Ci[cnz...nzmax-1] now free */
}
/* --- Construct new element ---------------------------------------- */
dk = 0;
nv[k] = -nvk; /* flag k as in Lk */
p = Cp[k];
pk1 = (elenk == 0) ? p : cnz; /* do in place if elen[k] == 0 */
pk2 = pk1;
for(k1 = 1; k1 <= elenk + 1; k1++)
{
if(k1 > elenk)
{
e = k; /* search the nodes in k */
pj = p; /* list of nodes starts at Ci[pj]*/
ln = len[k] - elenk; /* length of list of nodes in k */
}
else
{
e = Ci[p++]; /* search the nodes in e */
pj = Cp[e];
ln = len[e]; /* length of list of nodes in e */
}
for(k2 = 1; k2 <= ln; k2++)
{
i = Ci[pj++];
if((nvi = nv[i]) <= 0) continue; /* node i dead, or seen */
dk += nvi; /* degree[Lk] += size of node i */
nv[i] = -nvi; /* negate nv[i] to denote i in Lk*/
Ci[pk2++] = i; /* place i in Lk */
if(next[i] != -1) last[next[i]] = last[i];
if(last[i] != -1) /* remove i from degree list */
{
next[last[i]] = next[i];
}
else
{
head[degree[i]] = next[i];
}
}
if(e != k)
{
Cp[e] = amd_flip (k); /* absorb e into k */
w[e] = 0; /* e is now a dead element */
}
}
if(elenk != 0) cnz = pk2; /* Ci[cnz...nzmax] is free */
degree[k] = dk; /* external degree of k - |Lk\i| */
Cp[k] = pk1; /* element k is in Ci[pk1..pk2-1] */
len[k] = pk2 - pk1;
elen[k] = -2; /* k is now an element */
/* --- Find set differences ----------------------------------------- */
mark = internal::cs_wclear<StorageIndex>(mark, lemax, w, n); /* clear w if necessary */
for(pk = pk1; pk < pk2; pk++) /* scan 1: find |Le\Lk| */
{
i = Ci[pk];
if((eln = elen[i]) <= 0) continue;/* skip if elen[i] empty */
nvi = -nv[i]; /* nv[i] was negated */
wnvi = mark - nvi;
for(p = Cp[i]; p <= Cp[i] + eln - 1; p++) /* scan Ei */
{
e = Ci[p];
if(w[e] >= mark)
{
w[e] -= nvi; /* decrement |Le\Lk| */
}
else if(w[e] != 0) /* ensure e is a live element */
{
w[e] = degree[e] + wnvi; /* 1st time e seen in scan 1 */
}
}
}
/* --- Degree update ------------------------------------------------ */
for(pk = pk1; pk < pk2; pk++) /* scan2: degree update */
{
i = Ci[pk]; /* consider node i in Lk */
p1 = Cp[i];
p2 = p1 + elen[i] - 1;
pn = p1;
for(h = 0, d = 0, p = p1; p <= p2; p++) /* scan Ei */
{
e = Ci[p];
if(w[e] != 0) /* e is an unabsorbed element */
{
dext = w[e] - mark; /* dext = |Le\Lk| */
if(dext > 0)
{
d += dext; /* sum up the set differences */
Ci[pn++] = e; /* keep e in Ei */
h += e; /* compute the hash of node i */
}
else
{
Cp[e] = amd_flip (k); /* aggressive absorb. e->k */
w[e] = 0; /* e is a dead element */
}
}
}
elen[i] = pn - p1 + 1; /* elen[i] = |Ei| */
p3 = pn;
p4 = p1 + len[i];
for(p = p2 + 1; p < p4; p++) /* prune edges in Ai */
{
j = Ci[p];
if((nvj = nv[j]) <= 0) continue; /* node j dead or in Lk */
d += nvj; /* degree(i) += |j| */
Ci[pn++] = j; /* place j in node list of i */
h += j; /* compute hash for node i */
}
if(d == 0) /* check for mass elimination */
{
Cp[i] = amd_flip (k); /* absorb i into k */
nvi = -nv[i];
dk -= nvi; /* |Lk| -= |i| */
nvk += nvi; /* |k| += nv[i] */
nel += nvi;
nv[i] = 0;
elen[i] = -1; /* node i is dead */
}
else
{
degree[i] = std::min<StorageIndex> (degree[i], d); /* update degree(i) */
Ci[pn] = Ci[p3]; /* move first node to end */
Ci[p3] = Ci[p1]; /* move 1st el. to end of Ei */
Ci[p1] = k; /* add k as 1st element in of Ei */
len[i] = pn - p1 + 1; /* new len of adj. list of node i */
h %= n; /* finalize hash of i */
next[i] = hhead[h]; /* place i in hash bucket */
hhead[h] = i;
last[i] = h; /* save hash of i in last[i] */
}
} /* scan2 is done */
degree[k] = dk; /* finalize |Lk| */
lemax = std::max<StorageIndex>(lemax, dk);
mark = internal::cs_wclear<StorageIndex>(mark+lemax, lemax, w, n); /* clear w */
/* --- Supernode detection ------------------------------------------ */
for(pk = pk1; pk < pk2; pk++)
{
i = Ci[pk];
if(nv[i] >= 0) continue; /* skip if i is dead */
h = last[i]; /* scan hash bucket of node i */
i = hhead[h];
hhead[h] = -1; /* hash bucket will be empty */
for(; i != -1 && next[i] != -1; i = next[i], mark++)
{
ln = len[i];
eln = elen[i];
for(p = Cp[i]+1; p <= Cp[i] + ln-1; p++) w[Ci[p]] = mark;
jlast = i;
for(j = next[i]; j != -1; ) /* compare i with all j */
{
ok = (len[j] == ln) && (elen[j] == eln);
for(p = Cp[j] + 1; ok && p <= Cp[j] + ln - 1; p++)
{
if(w[Ci[p]] != mark) ok = 0; /* compare i and j*/
}
if(ok) /* i and j are identical */
{
Cp[j] = amd_flip (i); /* absorb j into i */
nv[i] += nv[j];
nv[j] = 0;
elen[j] = -1; /* node j is dead */
j = next[j]; /* delete j from hash bucket */
next[jlast] = j;
}
else
{
jlast = j; /* j and i are different */
j = next[j];
}
}
}
}
/* --- Finalize new element------------------------------------------ */
for(p = pk1, pk = pk1; pk < pk2; pk++) /* finalize Lk */
{
i = Ci[pk];
if((nvi = -nv[i]) <= 0) continue;/* skip if i is dead */
nv[i] = nvi; /* restore nv[i] */
d = degree[i] + dk - nvi; /* compute external degree(i) */
d = std::min<StorageIndex> (d, n - nel - nvi);
if(head[d] != -1) last[head[d]] = i;
next[i] = head[d]; /* put i back in degree list */
last[i] = -1;
head[d] = i;
mindeg = std::min<StorageIndex> (mindeg, d); /* find new minimum degree */
degree[i] = d;
Ci[p++] = i; /* place i in Lk */
}
nv[k] = nvk; /* # nodes absorbed into k */
if((len[k] = p-pk1) == 0) /* length of adj list of element k*/
{
Cp[k] = -1; /* k is a root of the tree */
w[k] = 0; /* k is now a dead element */
}
if(elenk != 0) cnz = p; /* free unused space in Lk */
}
/* --- Postordering ----------------------------------------------------- */
for(i = 0; i < n; i++) Cp[i] = amd_flip (Cp[i]);/* fix assembly tree */
for(j = 0; j <= n; j++) head[j] = -1;
for(j = n; j >= 0; j--) /* place unordered nodes in lists */
{
if(nv[j] > 0) continue; /* skip if j is an element */
next[j] = head[Cp[j]]; /* place j in list of its parent */
head[Cp[j]] = j;
}
for(e = n; e >= 0; e--) /* place elements in lists */
{
if(nv[e] <= 0) continue; /* skip unless e is an element */
if(Cp[e] != -1)
{
next[e] = head[Cp[e]]; /* place e in list of its parent */
head[Cp[e]] = e;
}
}
for(k = 0, i = 0; i <= n; i++) /* postorder the assembly tree */
{
if(Cp[i] == -1) k = internal::cs_tdfs<StorageIndex>(i, k, head, next, perm.indices().data(), w);
}
perm.indices().conservativeResize(n);
}
} // namespace internal
} // end namespace Eigen
#endif // EIGEN_SPARSE_AMD_H