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//------------------------------------------------------------------------------
// GB_AxB_saxpy3_fineHash_phase2: C=A*B (or with M in-place), fine Hash, phase2
//------------------------------------------------------------------------------
// SuiteSparse:GraphBLAS, Timothy A. Davis, (c) 2017-2022, All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0
//------------------------------------------------------------------------------
{
//--------------------------------------------------------------------------
// phase2: fine hash task, C(:,j)=A*B(:,j)
//--------------------------------------------------------------------------
// Given Hf [hash] split into (h,f)
// h == 0 , f == 0 : unlocked and unoccupied.
// h == i+1, f == 2 : unlocked, occupied by C(i,j). Hx is initialized.
// h == ..., f == 3 : locked.
// 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
// The mask M can be optionally checked, if it is dense and checked in
// place. This method is not used if M is present and sparse.
if (team_size == 1)
{
//----------------------------------------------------------------------
// single-threaded version
//----------------------------------------------------------------------
// the hash state 3 is not used, since only a single thread is
// doing all the work for this vector C(:,j).
// 0: if i seen for first time
// 2: if i seen already
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,j)
#ifdef GB_CHECK_MASK_ij
// check mask condition and skip if C(i,j)
// is protected by the mask
GB_CHECK_MASK_ij ;
#endif
GB_MULT_A_ik_B_kj ; // t = A(i,k) * B(k,j)
int64_t i_unlocked = ((i+1) << 2) + 2 ; // (i+1,2)
// find the entry i in the hash table
bool hf_unlocked = false ; // true if i found
bool hf_empty = false ; // true if empty slot found
int64_t hash ;
for (hash = GB_HASHF (i, hash_bits) ; ;
GB_REHASH (hash,i,hash_bits))
{
int64_t hf = Hf [hash] ; // grab the entry
hf_unlocked = (hf == i_unlocked) ;
hf_empty = (hf == 0) ;
if (hf_unlocked || hf_empty) break ;
}
if (hf_unlocked) // if true, update C(i,j)
{
// hash entry occuppied by C(i,j): update it
GB_HX_UPDATE (hash, t) ; // Hx [hash] += t
}
else // hf_empty: if true, load the hash entry with C(i,j)
{
// hash entry unoccuppied: fill it with C(i,j)
ASSERT (hf_empty) ;
GB_HX_WRITE (hash, t) ; // Hx [hash] = t
Hf [hash] = i_unlocked ; // unlock entry
}
}
}
}
else
{
//----------------------------------------------------------------------
// multi-threaded version
//----------------------------------------------------------------------
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,j)
#ifdef GB_CHECK_MASK_ij
// check mask condition and skip if C(i,j)
// is protected by the mask
GB_CHECK_MASK_ij ;
#endif
GB_MULT_A_ik_B_kj ; // t = A(i,k) * B(k,j)
int64_t i1 = i + 1 ; // i1 = one-based index
int64_t i_unlocked = (i1 << 2) + 2 ; // (i+1,2)
for (GB_HASH (i)) // find i in hash table
{
int64_t hf ;
GB_ATOMIC_READ
hf = Hf [hash] ; // grab the entry
#if GB_HAS_ATOMIC
if (hf == i_unlocked) // if true, update C(i,j)
{
GB_ATOMIC_UPDATE_HX (hash, t) ;// Hx [.]+=t
break ; // C(i,j) has been updated
}
#endif
int64_t h = (hf >> 2) ;
if (h == 0 || h == i1)
{
// h=0: unoccupied, h=i1: occupied by i
do // lock the entry
{
// do this atomically:
// { hf = Hf [hash] ; Hf [hash] |= 3 ; }
GB_ATOMIC_CAPTURE_INT64_OR (hf, Hf [hash], 3) ;
} while ((hf & 3) == 3) ; // owner: f=0 or 2
if (hf == 0) // f == 0
{
// C(i,j) is a new entry in C(:,j)
// Hx [hash] = t
GB_ATOMIC_WRITE_HX (hash, t) ;
GB_ATOMIC_WRITE
Hf [hash] = i_unlocked ; // unlock entry
break ;
}
if (hf == i_unlocked) // f == 2
{
// C(i,j) already appears in C(:,j)
// Hx [hash] += t
GB_ATOMIC_UPDATE_HX (hash, t) ;
GB_ATOMIC_WRITE
Hf [hash] = i_unlocked ; // unlock entry
break ;
}
// hash table occupied, but not with i
GB_ATOMIC_WRITE
Hf [hash] = hf ; // unlock with prior value
}
}
}
}
}
}
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