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//------------------------------------------------------------------------------
// GB_mex_reduce_terminal: [c,flag] = sum(A), reduce to scalar
//------------------------------------------------------------------------------
// SuiteSparse:GraphBLAS, Timothy A. Davis, (c) 2017-2022, All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0
//------------------------------------------------------------------------------
// Compute c=max(A,x) where all entries in A are known a priori to be <= x.
// x becomes the terminal value of a user-defined max monoid.
#include "GB_mex.h"
#define USAGE "c = GB_mex_reduce_terminal (A, terminal)"
#define FREE_ALL \
{ \
GrB_Matrix_free_(&A) ; \
GrB_BinaryOp_free_(&Max) ; \
GrB_Monoid_free_(&Max_Terminal) ; \
GB_mx_put_global (true) ; \
}
void maxdouble (double *z, const double *x, const double *y) ;
void maxdouble (double *z, const double *x, const double *y)
{
// this is not safe with NaNs
(*z) = ((*x) > (*y)) ? (*x) : (*y) ;
}
void mexFunction
(
int nargout,
mxArray *pargout [ ],
int nargin,
const mxArray *pargin [ ]
)
{
bool malloc_debug = GB_mx_get_global (true) ;
GrB_Matrix A = NULL ;
GrB_BinaryOp Max = NULL;
GrB_Monoid Max_Terminal = NULL ;
GrB_Info info ;
// check inputs
if (nargout > 1 || nargin < 1 || nargin > 2)
{
mexErrMsgTxt ("Usage: " USAGE) ;
}
#define GET_DEEP_COPY ;
#define FREE_DEEP_COPY ;
// get A (shallow copy)
A = GB_mx_mxArray_to_Matrix (pargin [0], "A input", false, true) ;
if (A == NULL)
{
FREE_ALL ;
mexErrMsgTxt ("A failed") ;
}
if (A->type != GrB_FP64)
{
FREE_ALL ;
mexErrMsgTxt ("A must be double precision") ;
}
// get the terminal value, if present. Default is 1.
double GET_SCALAR (1, double, terminal, 1) ;
// create the Max operator
info = GrB_BinaryOp_new (&Max,
(GxB_binary_function) maxdouble, GrB_FP64, GrB_FP64, GrB_FP64);
if (info != GrB_SUCCESS)
{
mexErrMsgTxt ("Max failed") ;
}
// create the Max monoid
info = GxB_Monoid_terminal_new_FP64_(&Max_Terminal, Max, (double) 0,
terminal) ;
if (info != GrB_SUCCESS)
{
mexErrMsgTxt ("Max_Terminal failed") ;
}
// reduce to a scalar
double c ;
info = GrB_Matrix_reduce_FP64_(&c, NULL, Max_Terminal, A, NULL) ;
if (info != GrB_SUCCESS)
{
printf ("error: %d\n", info) ;
mexErrMsgTxt ("reduce failed") ;
}
// printf ("result %g\n", c) ;
// return C as a scalar
pargout [0] = mxCreateDoubleScalar (c) ;
FREE_ALL ;
}
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