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//------------------------------------------------------------------------------
// GB_AxB_saxpy3_fineGus_phase2: C=A*B, saxpy3 method, fine Gustavson, phase2
//------------------------------------------------------------------------------
// SuiteSparse:GraphBLAS, Timothy A. Davis, (c) 2017-2022, All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0
//------------------------------------------------------------------------------
{
//--------------------------------------------------------------------------
// phase2: fine Gustavson task, C(:,j)=A*B(:,j)
//--------------------------------------------------------------------------
// Hf [i] is initially 0.
// 0 -> 3 : to lock, if i seen for first time
// 2 -> 3 : to lock, if i seen already
// 3 -> 2 : to unlock; now i has been seen
for ( ; pB < pB_end ; pB++) // scan B(:,j)
{
GB_GET_B_kj_INDEX ; // get index k of B(k,j)
GB_GET_A_k ; // get A(:,k)
if (aknz == 0) continue ;
GB_GET_B_kj ; // bkj = B(k,j)
// scan A(:,k)
for (int64_t pA = pA_start ; pA < pA_end ; pA++)
{
GB_GET_A_ik_INDEX ; // get index i of A(i,k)
GB_MULT_A_ik_B_kj ; // t = A(i,k) * B(k,j)
int8_t f ;
#if GB_IS_ANY_MONOID
//--------------------------------------------------------------
// C(i,j) += t ; with the ANY monoid
//--------------------------------------------------------------
GB_ATOMIC_READ
f = Hf [i] ; // grab the entry
if (f == 2) continue ; // check if already updated
GB_ATOMIC_WRITE_HX (i, t) ; // Hx [i] = t
#else
//--------------------------------------------------------------
// C(i,j) += t ; with all other monoids
//--------------------------------------------------------------
#if GB_HAS_ATOMIC
// if C(i,j) is already present (f==2), and the monoid can
// be done atomically, then do the atomic update. No need
// to modify Hf [i].
GB_ATOMIC_READ
f = Hf [i] ; // grab the entry
if (f == 2) // if true, update C(i,j)
{
GB_ATOMIC_UPDATE_HX (i, t) ; // Hx [i] += t
continue ; // C(i,j) has been updated
}
#endif
do // lock the entry
{
// do this atomically:
// { f = Hf [i] ; Hf [i] = 3 ; }
GB_ATOMIC_CAPTURE_INT8 (f, Hf [i], 3) ;
} while (f == 3) ; // lock owner gets f=0 or 2
if (f == 0)
{
// C(i,j) is a new entry
GB_ATOMIC_WRITE_HX (i, t) ; // Hx [i] = t
}
else // f == 2
{
// C(i,j) already appears in C(:,j)
GB_ATOMIC_UPDATE_HX (i, t) ; // Hx [i] += t
}
#endif
GB_ATOMIC_WRITE
Hf [i] = 2 ; // flag/unlock the entry
}
}
}
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