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/*
-- MAGMA (version 2.9.0) --
Univ. of Tennessee, Knoxville
Univ. of California, Berkeley
Univ. of Colorado, Denver
@date January 2025
@generated from sparse/control/magma_zselect.cpp, normal z -> s, Wed Jan 22 14:42:30 2025
@author Hartwig Anzt
*/
// in this file, many routines are taken from
// the IO functions provided by MatrixMarket
#include "magmasparse_internal.h"
#define SWAP(a, b) { tmp = a; a = b; b = tmp; }
magma_int_t
magma_spartition(
float *a,
magma_int_t size,
magma_int_t pivot,
magma_queue_t queue ) {
// using std::swap;
float tmp;
float pivotValue = a[pivot];
SWAP(a[pivot], a[size-1]);
int storePos = 0;
for(int loadPos=0; loadPos < size-1; loadPos++) {
if( MAGMA_S_ABS(a[loadPos]) < MAGMA_S_ABS(pivotValue) ) {
SWAP(a[loadPos], a[storePos]);
storePos++;
}
}
SWAP(a[storePos], a[size-1]);
return storePos;
}
magma_int_t
magma_smedian5(
float *a,
magma_queue_t queue ) {
// using std::swap;
float tmp;
float a0 = a[0];
float a1 = a[1];
float a2 = a[2];
float a3 = a[3];
float a4 = a[4];
if ( MAGMA_S_ABS(a1) < MAGMA_S_ABS( a0))
SWAP( a0, a1);
if ( MAGMA_S_ABS(a2) < MAGMA_S_ABS( a0))
SWAP( a0, a2);
if ( MAGMA_S_ABS(a3) < MAGMA_S_ABS( a0))
SWAP( a0, a3);
if ( MAGMA_S_ABS(a4) < MAGMA_S_ABS( a0))
SWAP( a0, a4);
if ( MAGMA_S_ABS(a2) < MAGMA_S_ABS( a1))
SWAP( a1, a2);
if ( MAGMA_S_ABS(a3) < MAGMA_S_ABS( a1))
SWAP( a1, a3);
if ( MAGMA_S_ABS(a4) < MAGMA_S_ABS( a1))
SWAP( a1, a4);
if ( MAGMA_S_ABS(a3) < MAGMA_S_ABS( a2))
SWAP( a2, a3);
if ( MAGMA_S_ABS(a4) < MAGMA_S_ABS( a2))
SWAP( a2, a4);
if ( MAGMA_S_ABS(a2) == MAGMA_S_ABS(a[0]))
return 0;
if ( MAGMA_S_ABS(a2) == MAGMA_S_ABS(a[1]))
return 1;
if ( MAGMA_S_ABS(a2) == MAGMA_S_ABS(a[2]))
return 2;
if ( MAGMA_S_ABS(a2) == MAGMA_S_ABS(a[3]))
return 3;
// else if ( MAGMA_S_ABS(a2) == MAGMA_S_ABS(a[4]))
return 4;
}
/**
Purpose
-------
An efficient implementation of Blum, Floyd,
Pratt, Rivest, and Tarjan's worst-case linear
selection algorithm
Derrick Coetzee, webmaster@moonflare.com
January 22, 2004
http://moonflare.com/code/select/select.pdf
Arguments
---------
@param[in,out]
a float*
array to select from
@param[in]
size magma_int_t
size of array
@param[in]
k magma_int_t
k-th smallest element
@param[in]
queue magma_queue_t
Queue to execute in.
@ingroup magmasparse_saux
********************************************************************/
extern "C"
magma_int_t
magma_sselect(
float *a,
magma_int_t size,
magma_int_t k,
magma_queue_t queue ) {
magma_int_t info = 0;
// using std::swap;
float tmp;
if (size < 5) {
for (int i=0; i<size; i++)
for (int j=i+1; j<size; j++)
if (MAGMA_S_ABS(a[j]) < MAGMA_S_ABS(a[i]))
SWAP(a[i], a[j]);
return info;
}
int groupNum = 0;
float *group = a;
for( ; groupNum*5 <= size-5; group += 5, groupNum++) {
SWAP(group[magma_smedian5(group, queue)], a[groupNum]);
}
int numMedians = size/5;
// Index of median of medians
int MOMIdx = numMedians/2;
magma_sselect(a, numMedians, MOMIdx, queue);
int newMOMIdx = magma_spartition(a, size, MOMIdx, queue);
if (k != newMOMIdx) {
if (k < newMOMIdx) {
magma_sselect(a, newMOMIdx, k, queue);
} else /* if (k > newMOMIdx) */ {
magma_sselect(a + newMOMIdx + 1, size - newMOMIdx - 1, k - newMOMIdx - 1, queue);
}
}
return info;
}
/**
Purpose
-------
An efficient implementation of Blum, Floyd,
Pratt, Rivest, and Tarjan's worst-case linear
selection algorithm
Derrick Coetzee, webmaster@moonflare.com
January 22, 2004
http://moonflare.com/code/select/select.pdf
Arguments
---------
@param[in,out]
a float*
array to select from
@param[in]
size magma_int_t
size of array
@param[in]
k magma_int_t
k-th smallest element
@param[in]
queue magma_queue_t
Queue to execute in.
@ingroup magmasparse_saux
********************************************************************/
extern "C"
magma_int_t
magma_sselectrandom(
float *a,
magma_int_t size,
magma_int_t k,
magma_queue_t queue ) {
magma_int_t info = 0;
//using std::swap;
float tmp;
if (size < 5) {
for (int i=0; i<size; i++)
for (int j=i+1; j<size; j++)
if (MAGMA_S_ABS(a[j]) < MAGMA_S_ABS(a[i]))
SWAP(a[i], a[j]);
return info;
}
int pivotIdx = magma_spartition(a, size, rand() % size, queue);
if (k != pivotIdx) {
if (k < pivotIdx) {
magma_sselectrandom(a, pivotIdx, k, queue);
} else /* if (k > pivotIdx) */ {
magma_sselectrandom(a + pivotIdx + 1, size - pivotIdx - 1, k - pivotIdx - 1, queue);
}
}
return info;
}
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