[9] RFR of 8032027: Add BigInteger square root methods

[Joseph D. Darcy]

Looks good Brian; thanks,

-Joe

On 12/10/2015 2:32 PM, Brian Burkhalter wrote:
> A new version is here:
>
> http://cr.openjdk.java.net/~bpb/8032027/webrev.05/ 
> <http://cr.openjdk.java.net/%7Ebpb/8032027/webrev.05/>
>
> I changed the test to verify these values:
>
>       Stream.Builder<BigInteger> sb = Stream.builder();
> int maxExponent = Double.MAX_EXPONENT + 1;
> for (int i = 1; i <= maxExponent; i++) {
>           BigInteger p2 = BigInteger.ONE.shiftLeft(i);
>           sb.add(p2.subtract(BigInteger.ONE));
>           sb.add(p2);
>           sb.add(p2.add(BigInteger.ONE));
>       }
>       sb.add((new BigDecimal(Double.MAX_VALUE)).toBigInteger());
>       sb.add((new 
> BigDecimal(Double.MAX_VALUE)).toBigInteger().add(BigInteger.ONE));
>   report("squareRoot for 2^N and 2^N - 1, 1 <= N <= Double.MAX_EXPONENT",
> sb.build().collect(Collectors.summingInt(f)));
>
> At line 1892 of the current version of MutableBigInteger I changed "if 
> (bitLength() < 63)" to "if (bitLength() <= 63)". I realized that in 
> that case the entire calculation might as well be done in longs so I 
> changed it accordingly. The modified test passes with this new revision.
>
> Thanks,
>
> Brian
>
> On Dec 9, 2015, at 6:11 PM, Joseph D. Darcy <Joe.Darcy at Oracle.Com 
> <mailto:Joe.Darcy at Oracle.Com>> wrote:
>
>> New version looks good.
>>
>> One more case to try: start with a BigInteger that would overflow to 
>> Double.POSITIVE_INFINITY when the doubleValue method was called. If 
>> this case doesn't take too long to run, it would be a fine additional 
>> case to add to the test. 2^1024 should be fine input value. More 
>> precisely,
>>
>>      (new 
>> BigDecimal(Double.MAX_VALUE)).toBigInteger().add(BigInteger.ONE);
>>
>> should do the trick. If the code passes with this value, you're okay 
>> to push. Well, while you're at it, might as well verify
>>
>>     (new BigDecimal(Double.MAX_VALUE)).toBigInteger()
>>
>> behaves well too ;-)
>
> On Dec 9, 2015, at 6:22 PM, Louis Wasserman <wasserman.louis at gmail.com 
> <mailto:wasserman.louis at gmail.com>> wrote:
>
>> Guava's tests check the explicit definition of square root (mentioned 
>> by Joe above) on 2^n +/- 1 for all n up to Double.MAX_EXPONENT + 1, 
>> because why not?
>