Hi Brian, Other than removing the // bug 8057793 comment on the new test method, this looks good to be pushed. Thanks, -Joe On 9/13/2014 7:56 AM, Brian Burkhalter wrote:
I forgot to add setScaleDoesNotMutateTest() to main() in ZeroScalingTests. D’oh! Here’s the corrected webrev:
http://cr.openjdk.java.net/~bpb/8057793/webrev.01/
Thanks,
Brian
On Sep 12, 2014, at 4:54 PM, Brian Burkhalter <brian.burkhalter@oracle.com> wrote:
Hello,
I created a formal webrev:
Issue: https://bugs.openjdk.java.net/browse/JDK-8057793 Webrev: http://cr.openjdk.java.net/~bpb/8057793/webrev.00/
Based on manual inspection of the revised code the patch looks good to me. The test submitted with the issue now succeeds as do all regression tests in jdk/test/java/math to which I also added the code from the test case in the issue report.
Note that this webrev is with respect to JDK 9.
Thanks,
Brian
On Sep 11, 2014, at 6:35 PM, Joe Darcy <joe.darcy@oracle.com> wrote:
Hello,
Hmmm. I haven't dived into the details of the code, but setScale calls out to divide functionality so it is plausible a bug in divide could cause a problem in setScale.
Thanks for the bug report,
-Joe
On 9/9/2014 1:30 AM, Robert Gibson wrote:
Hi there,
I came across a case in BigDecimal division where the dividend ends up getting mutated, which is rather strange for a seemingly immutable class! (It's a subset of the cases where the Burnikel-Ziegler algorithm is used, I haven't done the analysis to find out under which exact conditions it's triggered.)
The attached patch - against the JDK8 version - should fix the problem, at the cost of an extra array copy. Could somebody review and/or comment please?
Thanks, Robert
--- MutableBigInteger.java 2014-09-04 09:42:23.426815000 +0200 +++ MutableBigInteger.java.patched 2014-09-04 09:46:21.344132000 +0200 @@ -1261,19 +1261,20 @@ int sigma = (int) Math.max(0, n32 - b.bitLength()); // step 3: sigma = max{T | (2^T)*B < beta^n} MutableBigInteger bShifted = new MutableBigInteger(b); bShifted.safeLeftShift(sigma); // step 4a: shift b so its length is a multiple of n - safeLeftShift(sigma); // step 4b: shift this by the same amount + MutableBigInteger aShifted = new MutableBigInteger (this); + aShifted.safeLeftShift(sigma); // step 4b: shift a by the same amount - // step 5: t is the number of blocks needed to accommodate this plus one additional bit - int t = (int) ((bitLength()+n32) / n32); + // step 5: t is the number of blocks needed to accommodate a plus one additional bit + int t = (int) ((aShifted.bitLength()+n32) / n32); if (t < 2) { t = 2; } - // step 6: conceptually split this into blocks a[t-1], ..., a[0] - MutableBigInteger a1 = getBlock(t-1, t, n); // the most significant block of this + // step 6: conceptually split a into blocks a[t-1], ..., a[0] + MutableBigInteger a1 = aShifted.getBlock(t-1, t, n); // the most significant block of a // step 7: z[t-2] = [a[t-1], a[t-2]] - MutableBigInteger z = getBlock(t-2, t, n); // the second to most significant block + MutableBigInteger z = aShifted.getBlock(t-2, t, n); // the second to most significant block z.addDisjoint(a1, n); // z[t-2] // do schoolbook division on blocks, dividing 2-block numbers by 1-block numbers @@ -1284,7 +1285,7 @@ ri = z.divide2n1n(bShifted, qi); // step 8b: z = [ri, a[i-1]] - z = getBlock(i-1, t, n); // a[i-1] + z = aShifted.getBlock(i-1, t, n); // a[i-1] z.addDisjoint(ri, n); quotient.addShifted(qi, i*n); // update q (part of step 9) } @@ -1292,7 +1293,7 @@ ri = z.divide2n1n(bShifted, qi); quotient.add(qi); - ri.rightShift(sigma); // step 9: this and b were shifted, so shift back + ri.rightShift(sigma); // step 9: a and b were shifted, so shift back return ri; } }