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Enhance the SUM() aggregate (and related AVG() and TOTAL()) so that the running

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sum is accurate to about 100 bits.

FossilOrigin-Name: a915f15a916af698e0cef46c8b3e7ed11bda19349179d2d414073cd39c4cce24
This commit is contained in:
drh
2023-06-28 12:02:48 +00:00
parent 60783f47b2 d847c73153
commit 8fbb335d9f
6 changed files with 104 additions and 32 deletions
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40
src/util.c
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@@ -1750,3 +1750,43 @@ int sqlite3VListNameToNum(VList *pIn, const char *zName, int nName){
|| defined(SQLITE_ENABLE_STMT_SCANSTATUS)
# include "hwtime.h"
#endif
/***************************************************************************
** Double-Double arithmetic.
**
** Reference:
** T. J. Dekker, "A Floating-Point Technique for Extending the
** Available Precision". 1971-07-26.
*/
/* Compute z = (i64)x */
void sqlite3DDFromInt(i64 x, double *z){
z[0] = (double)x;
z[1] = (double)(x - (i64)z[0]);
}
/* Compute z = x + y */
void sqlite3DDAdd(double x, double xx, double y, double yy, double *z){
double r, s;
r = x + y;
if( fabs(x)>fabs(y) ){
s = x - r + y + yy + xx;
}else{
s = y - r + x + xx + yy;
}
z[0] = r+s;
z[1] = r - z[0] + s;
}
/* Compute z = x - y */
void sqlite3DDSub(double x, double xx, double y, double yy, double *z){
double r, s;
r = x - y;
if( fabs(x)>fabs(y) ){
s = x - r - y - yy + xx;
}else{
s = -y - r + x + xx - yy;
}
z[0] = r+s;
z[1] = r - z[0] + s;
}