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//------------------------------------------------------------------------------
// GB_ijlength: get the length and kind of an index list I
//------------------------------------------------------------------------------
// SuiteSparse:GraphBLAS, Timothy A. Davis, (c) 2017-2022, All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0
//------------------------------------------------------------------------------
// Determine the length of I, and process the colon notation I = begin:inc:end.
// No error checking is done.
#include "GB_ij.h"
// ensure an unsigned integer does not cause signed integer overflow
#define GB_LIMIT(u) (int64_t) (GB_IMIN (u, INT64_MAX))
void GB_ijlength // get the length and kind of an index list I
(
const GrB_Index *I, // list of indices (actual or implicit)
const int64_t ni, // length I, or special
const int64_t limit, // indices must be in the range 0 to limit-1
int64_t *nI, // actual length of I
int *Ikind, // kind of I: GB_ALL, GB_RANGE, GB_STRIDE, GB_LIST
int64_t Icolon [3] // begin:inc:end for all but GB_LIST
)
{
//--------------------------------------------------------------------------
// check inputs
//--------------------------------------------------------------------------
ASSERT (I != NULL) ;
ASSERT (limit >= 0) ;
ASSERT (limit <= GB_NMAX) ;
//--------------------------------------------------------------------------
// determine the length of I
//--------------------------------------------------------------------------
if (I == GrB_ALL)
{
//----------------------------------------------------------------------
// I = ":" = 0:limit-1
//----------------------------------------------------------------------
(*Ikind) = GB_ALL ;
Icolon [GxB_BEGIN] = 0 ;
Icolon [GxB_INC ] = 1 ;
Icolon [GxB_END ] = limit-1 ;
(*nI) = limit ;
}
else if (ni == GxB_RANGE)
{
//----------------------------------------------------------------------
// I = ibegin:iend
//----------------------------------------------------------------------
(*Ikind) = GB_RANGE ;
// the array I must have size at least 2
int64_t ibegin = GB_LIMIT (I [GxB_BEGIN]) ;
int64_t iend = GB_LIMIT (I [GxB_END ]) ;
ASSERT (ibegin >= 0) ;
if (ibegin == 0 && iend == limit-1)
{
// 0:limit-1 is the same as ":"
(*Ikind) = GB_ALL ;
}
Icolon [GxB_BEGIN] = ibegin ;
Icolon [GxB_INC ] = 1 ;
Icolon [GxB_END ] = iend ;
if (ibegin > iend)
{
// the list is empty
(*nI) = 0 ;
}
else // ibegin <= iend
{
// list ibegin:iend is not empty
(*nI) = (iend - ibegin + 1) ;
}
}
else if (ni == GxB_STRIDE)
{
//----------------------------------------------------------------------
// I = ibegin:iinc:iend where iinc >= 0
//----------------------------------------------------------------------
(*Ikind) = GB_STRIDE ;
// The array I must have size at least 3. It is an unsigned uint64_t
// array, so integers must be positive.
int64_t ibegin = GB_LIMIT (I [GxB_BEGIN]) ;
int64_t iinc = GB_LIMIT (I [GxB_INC ]) ;
int64_t iend = GB_LIMIT (I [GxB_END ]) ;
ASSERT (ibegin >= 0) ;
ASSERT (iinc >= 0) ;
ASSERT (iend >= 0) ;
if (iinc == 1)
{
if (ibegin == 0 && iend == limit-1)
{
// 0:1:limit-1 is the same as ":"
(*Ikind) = GB_ALL ;
}
else
{
// ibegin:1:iend is the same as ibegin:iend
(*Ikind) = GB_RANGE ;
}
}
// an increment of 0 means the list is empty
if (iinc == 0)
{
(*nI) = 0 ;
}
else // iinc > 0
{
if (ibegin > iend)
{
// the list ibegin:iinc:iend is empty (for example 10:1:0)
(*nI) = 0 ;
}
else // ibegin <= iend
{
// the list is non-empty (for example 4:2:7 = [4 6])
(*nI) = ((iend - ibegin) / iinc) + 1 ;
}
}
Icolon [GxB_BEGIN] = ibegin ;
Icolon [GxB_INC ] = iinc ;
Icolon [GxB_END ] = iend ;
}
else if (ni == GxB_BACKWARDS)
{
//----------------------------------------------------------------------
// I = ibegin:iinc:iend where iinc <= 0
//----------------------------------------------------------------------
(*Ikind) = GB_STRIDE ;
// The array I must have size at least 3. It is an unsigned uint64_t
// array, so integers must be positive.
int64_t ibegin = GB_LIMIT (I [GxB_BEGIN]) ;
int64_t iinc = GB_LIMIT (I [GxB_INC ]) ;
int64_t iend = GB_LIMIT (I [GxB_END ]) ;
ASSERT (iinc >= 0) ;
// the stride is backwards, so negate iinc
iinc = -iinc ;
ASSERT (ibegin >= 0) ;
ASSERT (iinc <= 0) ;
ASSERT (iend >= 0) ;
// an increment of 0 means the list is empty
if (iinc == 0)
{
(*nI) = 0 ;
}
else // iinc < 0
{
if (ibegin < iend)
{
// the list ibegin:iinc:iend is empty (for example 1:-1:10)
(*nI) = 0 ;
}
else
{
// the list is non-empty (for example 7:-2:4 = [7 5])
// two positive numbers are divided here
(*nI) = ((ibegin - iend) / (-iinc)) + 1 ;
}
}
Icolon [GxB_BEGIN] = ibegin ;
Icolon [GxB_INC ] = iinc ;
Icolon [GxB_END ] = iend ;
}
else
{
//----------------------------------------------------------------------
// I is an array of indices
//----------------------------------------------------------------------
(*Ikind) = GB_LIST ;
// not computed
Icolon [GxB_BEGIN] = 0 ;
Icolon [GxB_INC ] = 0 ;
Icolon [GxB_END ] = 0 ;
(*nI) = ni ;
}
}
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