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Update to use safe scaling algorithm from Reference-LAPACK PR 527 #4143

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merged 8 commits into from
Sep 1, 2023
Merged

Update to use safe scaling algorithm from Reference-LAPACK PR 527 #4143

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e08743d
Update to use safe scaling algorithm from Reference-LAPACK PR 527
martin-frbg Jul 12, 2023
0f2ce93
typo fix
martin-frbg Jul 13, 2023
7c75c8b
fix truncated edit
martin-frbg Jul 13, 2023
4cc232b
Merge branch 'xianyi:develop' into issue4130
martin-frbg Jul 13, 2023
5e1103b
Update rotg.c
martin-frbg Jul 13, 2023
04cdf5e
fix typo and missing declaration
martin-frbg Jul 13, 2023
a2a1845
update zrotg
martin-frbg Aug 31, 2023
42909ce
Merge branch 'xianyi:develop' into issue4130
martin-frbg Sep 1, 2023
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66 changes: 49 additions & 17 deletions interface/rotg.c
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Original file line number Diff line number Diff line change
@@ -1,9 +1,11 @@
#include <math.h>
#include <float.h>
#include "common.h"
#ifdef FUNCTION_PROFILE
#include "functable.h"
#endif


#ifndef CBLAS

void NAME(FLOAT *DA, FLOAT *DB, FLOAT *C, FLOAT *S){
Expand All @@ -14,35 +16,53 @@ void CNAME(FLOAT *DA, FLOAT *DB, FLOAT *C, FLOAT *S){

#endif

#ifdef DOUBLE
long double safmin = DBL_MIN;
#else
long double safmin = FLT_MIN;
#endif

#if defined(__i386__) || defined(__x86_64__) || defined(__ia64__) || defined(_M_X64) || defined(_M_IX86)

long double da = *DA;
long double db = *DB;
long double c;
long double s;
long double r, roe, z;
long double r, z;
long double sigma, dascal,dbscal;

long double ada = fabsl(da);
long double adb = fabsl(db);
long double scale = ada + adb;
long double maxab = MAX(ada,adb);
long double safmax;
long double scale;


#ifndef CBLAS
PRINT_DEBUG_NAME;
#else
PRINT_DEBUG_CNAME;
#endif

roe = db;
if (ada > adb) roe = da;

if (scale == ZERO) {
if (adb == ZERO) {
*C = ONE;
*S = ZERO;
*DA = ZERO;
*DB = ZERO;
} else if (ada == ZERO) {
*C = ZERO;
*S = ONE;
*DA = *DB;
*DB = ONE;
} else {
r = sqrt(da * da + db * db);
if (roe < 0) r = -r;
safmax = 1./safmin;
scale = MIN(MAX(safmin,maxab), safmax);
if (ada > adb)
sigma = copysign(1.,da);
else
sigma = copysign(1.,db);
dascal = da / scale;
dbscal = db / scale;
r = sigma * (scale * sqrt(dascal * dascal + dbscal * dbscal));
c = da / r;
s = db / r;
z = ONE;
Expand All @@ -65,32 +85,44 @@ void CNAME(FLOAT *DA, FLOAT *DB, FLOAT *C, FLOAT *S){
FLOAT db = *DB;
FLOAT c = *C;
FLOAT s = *S;
FLOAT r, roe, z;
FLOAT sigma;
FLOAT r, z;

FLOAT ada = fabs(da);
FLOAT adb = fabs(db);
FLOAT scale = ada + adb;
FLOAT maxab = MAX(ada,adb);
long double safmax ;
FLOAT scale ;

safmax = 1./safmin;
scale = MIN(MAX(safmin,maxab), safmax);

if (ada > adb)
sigma = copysign(1.,da);
else
sigma = copysign(1.,db);

#ifndef CBLAS
PRINT_DEBUG_NAME;
#else
PRINT_DEBUG_CNAME;
#endif

roe = db;
if (ada > adb) roe = da;

if (scale == ZERO) {
if (adb == ZERO) {
*C = ONE;
*S = ZERO;
*DA = ZERO;
*DB = ZERO;
} else if (ada == ZERO) {
*C = ZERO;
*S = ONE;
*DA = *DB;
*DB = ONE;
} else {
FLOAT aa = da / scale;
FLOAT bb = db / scale;

r = scale * sqrt(aa * aa + bb * bb);
if (roe < 0) r = -r;
r = sigma * scale * sqrt(aa * aa + bb * bb);
c = da / r;
s = db / r;
z = ONE;
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