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//------------------------------------------------------------------------------
// GB_AxB_dot3_one_slice: slice the entries and vectors of a single matrix
//------------------------------------------------------------------------------
// SuiteSparse:GraphBLAS, Timothy A. Davis, (c) 2017-2022, All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0
//------------------------------------------------------------------------------
// Constructs a set of tasks that slice a single input matrix M. This function
// is currently only used by GB_AxB_dot3, to slice the mask matrix M, which has
// the same pattern as the output matrix C. However, this function is a very
// simple general-purpose method for slicing a single matrix. It could be
// called GB_one_slice, and used for other methods as well.
#define GB_FREE_WORKSPACE \
{ \
GB_WERK_POP (Coarse, int64_t) ; \
}
#define GB_FREE_ALL \
{ \
GB_FREE_WORKSPACE ; \
GB_FREE_WORK (&TaskList, TaskList_size) ; \
}
#include "GB_mxm.h"
#define GB_NTASKS_PER_THREAD 256
//------------------------------------------------------------------------------
// GB_AxB_dot3_one_slice
//------------------------------------------------------------------------------
GrB_Info GB_AxB_dot3_one_slice
(
// output:
GB_task_struct **p_TaskList, // array of structs
size_t *p_TaskList_size, // size of TaskList
int *p_ntasks, // # of tasks constructed
int *p_nthreads, // # of threads to use
// input:
const GrB_Matrix M, // matrix to slice
GB_Context Context
)
{
//--------------------------------------------------------------------------
// check inputs
//--------------------------------------------------------------------------
ASSERT (p_TaskList != NULL) ;
ASSERT (p_TaskList_size != NULL) ;
ASSERT (p_ntasks != NULL) ;
ASSERT (p_nthreads != NULL) ;
ASSERT_MATRIX_OK (M, "M for dot3_one_slice", GB0) ;
// the pattern of M is not accessed
ASSERT (GB_ZOMBIES_OK (M)) ;
ASSERT (GB_JUMBLED_OK (M)) ;
ASSERT (GB_PENDING_OK (M)) ;
ASSERT (!GB_IS_BITMAP (M)) ;
ASSERT (!GB_IS_FULL (M)) ;
(*p_TaskList ) = NULL ;
(*p_TaskList_size) = 0 ;
(*p_ntasks ) = 0 ;
(*p_nthreads ) = 1 ;
//--------------------------------------------------------------------------
// determine # of threads to use
//--------------------------------------------------------------------------
GB_GET_NTHREADS_MAX (nthreads_max, chunk, Context) ;
//--------------------------------------------------------------------------
// get M
//--------------------------------------------------------------------------
const int64_t *restrict Mp = M->p ;
const int64_t mnz = GB_nnz_held (M) ;
const int64_t mnvec = M->nvec ;
const int64_t mvlen = M->vlen ;
//--------------------------------------------------------------------------
// allocate the initial TaskList
//--------------------------------------------------------------------------
GB_WERK_DECLARE (Coarse, int64_t) ;
int ntasks1 = 0 ;
int nthreads = GB_nthreads (mnz, chunk, nthreads_max) ;
GB_task_struct *restrict TaskList = NULL ; size_t TaskList_size = 0 ;
int max_ntasks = 0 ;
int ntasks = 0 ;
int ntasks0 = (nthreads == 1) ? 1 : (GB_NTASKS_PER_THREAD * nthreads) ;
GB_REALLOC_TASK_WORK (TaskList, ntasks0, max_ntasks) ;
//--------------------------------------------------------------------------
// check for quick return for a single task
//--------------------------------------------------------------------------
if (mnvec == 0 || ntasks0 == 1)
{
// construct a single coarse task that does all the work
TaskList [0].kfirst = 0 ;
TaskList [0].klast = mnvec-1 ;
(*p_TaskList ) = TaskList ;
(*p_TaskList_size) = TaskList_size ;
(*p_ntasks ) = (mnvec == 0) ? 0 : 1 ;
(*p_nthreads ) = 1 ;
return (GrB_SUCCESS) ;
}
//--------------------------------------------------------------------------
// determine # of threads and tasks
//--------------------------------------------------------------------------
double target_task_size = ((double) mnz) / (double) (ntasks0) ;
target_task_size = GB_IMAX (target_task_size, chunk) ;
ntasks1 = ((double) mnz) / target_task_size ;
ntasks1 = GB_IMAX (ntasks1, 1) ;
//--------------------------------------------------------------------------
// slice the work into coarse tasks
//--------------------------------------------------------------------------
GB_WERK_PUSH (Coarse, ntasks1 + 1, int64_t) ;
if (Coarse == NULL)
{
// out of memory
GB_FREE_ALL ;
return (GrB_OUT_OF_MEMORY) ;
}
GB_pslice (Coarse, Mp, mnvec, ntasks1, false) ;
//--------------------------------------------------------------------------
// construct all tasks, both coarse and fine
//--------------------------------------------------------------------------
for (int t = 0 ; t < ntasks1 ; t++)
{
//----------------------------------------------------------------------
// coarse task operates on M (:, k:klast)
//----------------------------------------------------------------------
int64_t k = Coarse [t] ;
int64_t klast = Coarse [t+1] - 1 ;
if (k >= mnvec)
{
//------------------------------------------------------------------
// all tasks have been constructed
//------------------------------------------------------------------
break ;
}
else if (k < klast)
{
//------------------------------------------------------------------
// coarse task has 2 or more vectors
//------------------------------------------------------------------
// This is a non-empty coarse-grain task that does two or more
// entire vectors of M and C, vectors k:klast, inclusive.
GB_REALLOC_TASK_WORK (TaskList, ntasks + 1, max_ntasks) ;
TaskList [ntasks].kfirst = k ;
TaskList [ntasks].klast = klast ;
ntasks++ ;
}
else
{
//------------------------------------------------------------------
// coarse task has 0 or 1 vectors
//------------------------------------------------------------------
// As a coarse-grain task, this task is empty or does a single
// vector, k. Vector k must be removed from the work done by this
// and any other coarse-grain task, and split into one or more
// fine-grain tasks.
for (int tt = t ; tt < ntasks1 ; tt++)
{
// remove k from the initial slice tt
if (Coarse [tt] == k)
{
// remove k from task tt
Coarse [tt] = k+1 ;
}
else
{
// break, k not in task tt
break ;
}
}
//------------------------------------------------------------------
// determine the # of fine-grain tasks to create for vector k
//------------------------------------------------------------------
int64_t mknz = (Mp == NULL) ? mvlen : (Mp [k+1] - Mp [k]) ;
int nfine = ((double) mknz) / target_task_size ;
nfine = GB_IMAX (nfine, 1) ;
// make the TaskList bigger, if needed
GB_REALLOC_TASK_WORK (TaskList, ntasks + nfine, max_ntasks) ;
//------------------------------------------------------------------
// create the fine-grain tasks
//------------------------------------------------------------------
if (nfine == 1)
{
//--------------------------------------------------------------
// this is a single coarse task for all of vector k
//--------------------------------------------------------------
TaskList [ntasks].kfirst = k ;
TaskList [ntasks].klast = k ;
ntasks++ ;
}
else
{
//--------------------------------------------------------------
// slice vector M(:,k) into nfine fine tasks
//--------------------------------------------------------------
ASSERT (ntasks < max_ntasks) ;
for (int tfine = 0 ; tfine < nfine ; tfine++)
{
// this fine task operates on vector M(:,k)
TaskList [ntasks].kfirst = k ;
TaskList [ntasks].klast = -1 ;
// slice M(:,k) for this task
int64_t p1, p2 ;
GB_PARTITION (p1, p2, mknz, tfine, nfine) ;
int64_t pM_start = GBP (Mp, k, mvlen) ;
int64_t pM = pM_start + p1 ;
int64_t pM_end = pM_start + p2 ;
TaskList [ntasks].pM = pM ;
TaskList [ntasks].pM_end = pM_end ;
ASSERT (TaskList [ntasks].pM <= TaskList [ntasks].pM_end) ;
ntasks++ ;
}
}
}
}
ASSERT (ntasks <= max_ntasks) ;
//--------------------------------------------------------------------------
// free workspace and return result
//--------------------------------------------------------------------------
GB_FREE_WORKSPACE ;
(*p_TaskList ) = TaskList ;
(*p_TaskList_size) = TaskList_size ;
(*p_ntasks ) = ntasks ;
(*p_nthreads ) = nthreads ;
return (GrB_SUCCESS) ;
}
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