Apache/commons-math
1
0
Fork 0
mirror of https://github.com/apache/commons-math.git synced 2025-02-06 18:18:56 +00:00
Code Issues Packages Projects Releases Wiki Activity

MATH-476 FastMath code contains 'magic' numbers

Browse Source 
Extracted 2^52 value as a constant

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1061625 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Sebastian Bazley 2011-01-21 04:34:55 +00:00
parent d4005bbd6e
commit 031654a93c
1 changed files with 9 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
src/main/java/org/apache/commons/math/util/FastMath.java
View File

@ -166,6 +166,9 @@ public class FastMath {
*/
private static final double HEX_40000000 = 1073741824.0;
/** 2^52 - double numbers this large must be integral (no fraction) or NaN or Infinite */
private static final double TWO_POWER_52 = 4503599627370496.0;
// Initialize tables
static {
int i;
@ -1291,7 +1294,7 @@ public class FastMath {
// y is the most significant 10 bits of the mantissa
//double y = Double.longBitsToDouble(bits & 0xfffffc0000000000L);
//double epsilon = (x - y) / y;
double epsilon = (double)(bits & 0x3ffffffffffL) / (4503599627370496.0 + (bits & 0x000ffc0000000000L));
double epsilon = (double)(bits & 0x3ffffffffffL) / (TWO_POWER_52 + (bits & 0x000ffc0000000000L));
double lnza = 0.0;
double lnzb = 0.0;
@ -1306,7 +1309,7 @@ public class FastMath {
/* Need a more accurate epsilon, so adjust the division. */
double numer = (double)(bits & 0x3ffffffffffL);
double denom = 4503599627370496.0 + (bits & 0x000ffc0000000000L);
double denom = TWO_POWER_52 + (bits & 0x000ffc0000000000L);
aa = numer - xa*denom - xb * denom;
xb += aa / denom;
@ -1579,7 +1582,7 @@ public class FastMath {
/* Handle special case x<0 */
if (x < 0) {
// y is an even integer in this case
if (y >= 4503599627370496.0 || y <= -4503599627370496.0) {
if (y >= TWO_POWER_52 || y <= -TWO_POWER_52) {
return pow(-x, y);
}
@ -2420,8 +2423,8 @@ public class FastMath {
}
/* Convert to double */
double tmpA = (prod2A >>> 12) / 4503599627370496.0; // High order 52 bits
double tmpB = (((prod2A & 0xfffL) << 40) + (prod2B >>> 24)) / 4503599627370496.0 / 4503599627370496.0; // Low bits
double tmpA = (prod2A >>> 12) / TWO_POWER_52; // High order 52 bits
double tmpB = (((prod2A & 0xfffL) << 40) + (prod2B >>> 24)) / TWO_POWER_52 / TWO_POWER_52; // Low bits
double sumA = tmpA + tmpB;
double sumB = -(sumA - tmpA - tmpB);
@ -3499,7 +3502,7 @@ public class FastMath {
return x;
}
if (x >= 4503599627370496.0 || x <= -4503599627370496.0) {
if (x >= TWO_POWER_52 || x <= -TWO_POWER_52) {
return x;
}