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diff --git a/src/intersim2/arbiters/matrix_arb.cpp b/src/intersim2/arbiters/matrix_arb.cpp
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+// $Id: matrix_arb.cpp 5188 2012-08-30 00:31:31Z dub $
+
+/*
+ Copyright (c) 2007-2012, Trustees of The Leland Stanford Junior University
+ All rights reserved.
+
+ Redistribution and use in source and binary forms, with or without
+ modification, are permitted provided that the following conditions are met:
+
+ Redistributions of source code must retain the above copyright notice, this 
+ list of conditions and the following disclaimer.
+ Redistributions in binary form must reproduce the above copyright notice, this
+ list of conditions and the following disclaimer in the documentation and/or
+ other materials provided with the distribution.
+
+ THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 
+ DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
+ ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+// ----------------------------------------------------------------------
+//
+//  Matrix: Matrix Arbiter
+//
+// ----------------------------------------------------------------------
+
+#include "matrix_arb.hpp"
+#include <iostream>
+using namespace std ;
+
+MatrixArbiter::MatrixArbiter( Module *parent, const string &name, int size )
+  : Arbiter( parent, name, size ), _last_req(-1) {
+  _matrix.resize(size);
+  for ( int i = 0 ; i < size ; i++ ) {
+    _matrix[i].resize(size);
+    for ( int j = 0; j < i; j++ ) {
+      _matrix[i][j] = 1;
+    }
+  }
+}
+
+void MatrixArbiter::PrintState() const  {
+  cout << "Priority Matrix: " << endl ;
+  for ( int r = 0; r < _size ; r++ ) {
+    for ( int c = 0 ; c < _size ; c++ ) {
+      cout << _matrix[r][c] << " " ;
+    }
+    cout << endl ;
+  }
+  cout << endl ;
+}
+
+void MatrixArbiter::UpdateState() {
+  // update priority matrix using last grant
+  if ( _selected > -1 ) {
+    for ( int i = 0; i < _size ; i++ ) {
+      if( _selected != i ) {
+	_matrix[_selected][i] = 0 ;
+	_matrix[i][_selected] = 1 ;
+      }
+    }
+  }
+}
+
+void MatrixArbiter::AddRequest( int input, int id, int pri )
+{
+  _last_req = input;
+  Arbiter::AddRequest(input, id, pri);
+}
+
+int MatrixArbiter::Arbitrate( int* id, int* pri ) {
+  
+  // avoid running arbiter if it has not recevied at least two requests
+  // (in this case, requests and grants are identical)
+  if ( _num_reqs < 2 ) {
+    
+    _selected = _last_req ;
+    
+  } else {
+    
+    _selected = -1 ;
+
+    for ( int input = 0 ; input < _size ; input++ ) {
+      if(_request[input].valid) {
+	
+	bool grant = true;
+	for ( int i = 0 ; i < _size ; i++ ) {
+	  if ( _request[i].valid &&
+	       ( ( ( _request[i].pri == _request[input].pri ) &&
+		   _matrix[i][input]) ||
+		 ( _request[i].pri > _request[input].pri )
+		 ) ) {
+	    grant = false ;
+	    break ;
+	  }
+	}
+	
+	if ( grant ) {
+	  _selected = input ;
+	  break ; 
+	}
+      }
+      
+    }
+  }
+    
+  return Arbiter::Arbitrate(id, pri);
+}
+
+void MatrixArbiter::Clear()
+{
+  _last_req = -1;
+  Arbiter::Clear();
+}