Hello,
Could you consider an exponentiation by squaring (in the main release)
instead of current n-multiplication of exponents? I've observed that an
average time spent in sqlite3AtoF() is greatly reduced by 12% to over
30%, depending on an exponent's magnitude and a compiler. It is nothing
more then 3 lines of code and a noticeable advantage, for example:
======
--- util.c 2017-10-25 02:25:56.000000000 +0200
+++ util-esqr.c 2017-12-25 07:02:20.101110300 +0100
@@ -475,11 +475,12 @@
if( e==0 ){
/*OPTIMIZATION-IF-TRUE*/
result = (double)s;
}else{
- LONGDOUBLE_TYPE scale = 1.0;
+ LONGDOUBLE_TYPE scale = 1.0, t;
/* attempt to handle extremely small/large numbers better */
if( e>307 ){
/*OPTIMIZATION-IF-TRUE*/
if( e<342 ){
/*OPTIMIZATION-IF-TRUE*/
- while( e%308 ) { scale *= 1.0e+1; e -= 1; }
+ for ( e -= 308, t = 1.0e+1; 1 < e; e >>= 1, t *= t ) { if ( 1
& e ) scale *= t; }
+ if ( e ) scale *= t;
if( esign<0 ){
result = s / scale;
result /= 1.0e+308;
@@ -499,10 +500,8 @@
}
}
}else{
- /* 1.0e+22 is the largest power of 10 than can be
- ** represented exactly. */
- while( e%22 ) { scale *= 1.0e+1; e -= 1; }
- while( e>0 ) { scale *= 1.0e+22; e -= 22; }
+ for ( t = 1.0e+1; 1 < e; e >>= 1, t *= t ) { if ( 1 & e ) scale
*= t; }
+ scale *= t;
if( esign<0 ){
result = s / scale;
}else{
======
-- best regards
Cezary H. Noweta
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