CAS precision

10122015, 07:19 PM
Post: #1




CAS precision
Does a CAS program behave like builtin CAS commands in the way it handles floating point numbers and intermediate results?
Graph 3D  QPI  SolveSys 

10132015, 06:44 AM
Post: #2




RE: CAS precision
Yes, it should.


10162015, 03:16 PM
(This post was last modified: 10162015 03:21 PM by Han.)
Post: #3




RE: CAS precision
Does using return(param) within a subroutine truncate any digits? One of the issues I have found is that matrix multiplication (row vector times column vector) gives me a slightly different result than calling a subroutine that does the multiplication and returns the inner product (the former is more accurate than the latter it seems). That is, t:=b*v; seems more accurate in the long run (which I use later on to for something else) than t:=inprod(b,v); where inprod(); is a cas routine whose code is:
Code: inprod(b,v):= Graph 3D  QPI  SolveSys 

10172015, 04:05 PM
Post: #4




RE: CAS precision
This might happen because the intermediate conversions double <> giac::gen are not exactly the same in both processes. Every time a double is stored in a giac::gen, the 5 less significant bits are replaced by the type field, and in the other direction the 5 less significant bits are set to 0.


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