Re: {Precision@N[2^1024],N[2^1024]===$MaxMachineNumber}
- To: mathgroup at smc.vnet.net
- Subject: [mg80721] Re: {Precision@N[2^1024],N[2^1024]===$MaxMachineNumber}
- From: Bill Rowe <readnewsciv at sbcglobal.net>
- Date: Thu, 30 Aug 2007 02:31:20 -0400 (EDT)
On 8/29/07 at 4:10 AM, chris at chiasson.name (Chris Chiasson) wrote: >on my computer, this command gives {15.9546,False} >However, I think the result is supposed to be >{MachinePrecision,True} >Is there something wrong with N? I don't think so. On my machine there is a slight difference between $MaxMachineNumber and N[2^1024] that can be seen using RealDigits In[1]:= RealDigits[2^1024 // N] Out[1]= {{1,7,9,7,6,9,3,1,3,4,8,6,2,3,1,6},309} In[2]:= RealDigits[$MaxMachineNumber] Out[2]= {{1,7,9,7,6,9,3,1,3,4,8,6,2,3,1,5},309} In[3]:= $Version Out[3]= 6.0 for Mac OS X PowerPC (32-bit) (June 19, 2007) Hence, the false result returned when testing if these two numbers are identical >My computer is an Athlon XP running Windows XP SP2. >Also, why does ByteCount@$MaxMachineNumber give 16 ? I'm sure I am >missing something, but I thought a double precision floating point >number would only take up 8 bytes. ByteCount returns the amount of memory Mathematica uses internally to store an object. This will be the number of bytes the object takes plus any additional information or tags Mathematica associates with the object. The point is the value returned by ByteCount cannot be assumed to be just the amount of memory needed store a number. -- To reply via email subtract one hundred and four