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//------------------------------------------------------------------------------
// LAGraph_SwapEdges: randomly swaps edges in a graph
//------------------------------------------------------------------------------
// LAGraph, (c) 2019-2022 by The LAGraph Contributors, All Rights Reserved.
// SPDX-License-Identifier: BSD-2-Clause
//
// For additional details (including references to third party source code and
// other files) see the LICENSE file or contact permission@sei.cmu.edu. See
// Contributors.txt for a full list of contributors. Created, in part, with
// funding and support from the U.S. Government (see Acknowledgments.txt file).
// DM22-0790
// Contributed by Gabriel Gomez, Texas A&M University
//------------------------------------------------------------------------------
// References:
// R. Milo, N. Kashtan, S. Itzkovitz, M. E. J. Newman, and U. Alon, “On the
// uniform generation of random graphs with prescribed degree sequences,” 2004.
#include "LG_internal.h"
#include "LAGraphX.h"
int LAGraph_SwapEdges
(
// output
LAGraph_Graph *G_new, // A new graph with the same degree for each node
double *pQ, // Actual Swaps proformed per edge
// input: not modified
const LAGraph_Graph G, // Graph to be randomized.
double Q, // Swaps per edge
char *msg
)
{
LG_ASSERT(pQ != NULL, GrB_NULL_POINTER);
LG_ASSERT(Q > 0.0, GrB_INVALID_VALUE);
GrB_Index numEdges = 0;
GrB_Matrix_nvals(&numEdges, G->A) ;
numEdges /= 2;
uint64_t pSwaps = 0;
int info = LAGr_SwapEdges(
G_new, &pSwaps, G, .70, .10,
(uint64_t) (numEdges * Q), 891234789234ull, msg) ;
*pQ = ((double) pSwaps / (double) numEdges);
return info;
}