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[base] Fix commit ab02d9e8.

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* src/base/ftbbox.c (BBox_Cubic_Check): Change scaling to msb of 22.
This commit is contained in:
Alexei Podtelezhnikov 2013-02-22 23:58:57 -05:00
parent f9434dba81
commit 2ba18ba1ce
2 changed files with 14 additions and 8 deletions
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6
ChangeLog
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@ -1,3 +1,9 @@
2013-02-23 Alexei Podtelezhnikov <apodtele@gmail.com>
[base] Fix commit ab02d9e8.
* src/base/ftbbox.c (BBox_Cubic_Check): Change scaling to msb of 22.
2013-02-19 Alexei Podtelezhnikov <apodtele@gmail.com>
[base] New bisecting BBox_Cubic_Check (disabled).

16
src/base/ftbbox.c
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@ -412,11 +412,11 @@
/* These values must fit into a single 16.16 value. */
/* */
/* We normalize a, b, and c to `8.16' fixed-point values to ensure */
/* that its product is held in a `16.16' value. Necessarily, */
/* we need to shift `a', `b', and `c' so that the most significant */
/* bit of their absolute values is at _most_ at position 23. */
/* that their product is held in a `16.16' value including the sign. */
/* Necessarily, we need to shift `a', `b', and `c' so that the most */
/* significant bit of their absolute values is at position 22. */
/* */
/* This also means that we are using 24 bits of precision to compute */
/* This also means that we are using 23 bits of precision to compute */
/* the zeros, independently of the range of the original polynomial */
/* coefficients. */
/* */
@ -427,11 +427,11 @@
shift = FT_MSB( FT_ABS( a ) | FT_ABS( b ) | FT_ABS( c ) );
if ( shift > 23 )
if ( shift > 22 )
{
shift -= 23;
shift -= 22;
/* this loses some bits of precision, but we use 24 of them */
/* this loses some bits of precision, but we use 23 of them */
/* for the computation anyway */
a >>= shift;
b >>= shift;
@ -439,7 +439,7 @@
}
else
{
shift = 23 - shift;
shift = 22 - shift;
a <<= shift;
b <<= shift;