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/*
* Copyright (c) 2016 Cisco and/or its affiliates.
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <vppinfra/ptclosure.h>
u8 ** clib_ptclosure_alloc (int n)
{
u8 ** rv = 0;
u8 * row;
int i;
ASSERT (n > 0);
vec_validate (rv, n-1);
for (i = 0; i < n; i++)
{
row = 0;
vec_validate (row, n-1);
rv[i] = row;
}
return rv;
}
void clib_ptclosure_free (u8 ** ptc)
{
u8 * row;
int n = vec_len (ptc);
int i;
ASSERT (n > 0);
for (i = 0; i < n; i++)
{
row = ptc[i];
vec_free (row);
}
vec_free (ptc);
}
void clib_ptclosure_copy (u8 ** dst, u8 **src)
{
int i, n;
u8 * src_row, * dst_row;
n = vec_len (dst);
for (i = 0; i < vec_len(dst); i++)
{
src_row = src[i];
dst_row = dst[i];
clib_memcpy (dst_row, src_row, n);
}
}
/*
* compute the positive transitive closure
* of a relation via Warshall's algorithm.
*
* Ref:
* Warshall, Stephen (January 1962). "A theorem on Boolean matrices".
* Journal of the ACM 9 (1): 11–12.
*
* foo[i][j] = 1 means that item i
* "bears the relation" to item j.
*
* For example: "item i must be before item j"
*
* You could use a bitmap, but since the algorithm is
* O(n**3) in the first place, large N is inadvisable...
*
*/
u8 ** clib_ptclosure (u8 ** orig)
{
int i, j, k;
int n;
u8 ** prev, ** cur;
n = vec_len (orig);
prev = clib_ptclosure_alloc (n);
cur = clib_ptclosure_alloc (n);
clib_ptclosure_copy (prev, orig);
for (k = 0; k < n; k++)
{
for (i = 0; i < n; i++)
{
for (j = 0; j < n; j++)
{
cur[i][j] = prev[i][j] || (prev[i][k] && prev[k][j]);
}
}
clib_ptclosure_copy (prev, cur);
}
clib_ptclosure_free (prev);
return cur;
}
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