Wrong logarithm of BigInteger when size of BigInteger exceeds ¼ gigabyte

Wrong logarithm of BigInteger when size of BigInteger exceeds ¼ gigabyte by JeppeSN1

Closed

as Won't Fix Help for as Won't Fix

Type:	Bug
ID:	776946
Opened:	1/18/2013 2:19:44 PM
Access Restriction:	Public

Workaround(s)

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User(s) can reproduce this bug

When the size of a (positive) BigInteger (from System.Numerics.dll) exceeds ¼ gigabyte, the logarithm returned by BigInteger.Log is incorrect. In the calculation, an Int32 accidentally overflows and therefore it may become negative.

Please also see http://stackoverflow.com/questions/14402877/ for a discussion of the problem.

This is seen in .NET 4.5 and .NET 4.0.

Details (expand)

.NET Framework 4.5

Run the following Visual C# code:

var i = BigInteger.Pow(256, 300000000);
double log = BigInteger.Log(i);
Console.WriteLine(log);

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A negative value -1313491238.4757 is output. As the number i is not between 0 and 1, its logarithm should not be negative.

The value should be positive 1663553233.34387.
Mathematically, equal to 300000000.0 * Math.Log(256.0);

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Posted by Microsoft on 2/21/2013 at 7:24 AM

Thank you for your feedback. We are not going to be able to address this issue in our next release due to other priorities.

Regards,
Immo Landwerth
.NET Framework team

Posted by Microsoft on 2/21/2013 at 7:23 AM

Thank you for your feedback. We are not going to be able to address this issue in our next release due to other priorities.

Regards,
Immo Landwerth
.NET Framework team

Posted by Microsoft on 1/20/2013 at 8:28 PM

Thanks for your feedback.

We are rerouting this issue to the appropriate group within the Visual Studio Product Team for triage and resolution. These specialized experts will follow-up with your issue.

Posted by Microsoft on 1/18/2013 at 2:51 PM

Thank you for your feedback, we are currently reviewing the issue you have submitted. If this issue is urgent, please contact support directly(http://support.microsoft.com)