HOME and CAS unexpected behavior

[mmadurga]

Hi all,

One of my students mentioned to me that he was getting zero when calculating the result of a finite integral in HOME.

I already had the solutionI calculated using a table of integrals so I could easily evaluate it in both HOME and CAS, and, lo and behold, I get 0.000E0 in HOME, 7.1054E-15 in CAS.

The expression to evaluate is

EXP(-2r/a) * (-2r^2/a^2 - 2r/a - 1) + 1

with r=0.877E-15 and a =5.290E-11

Any idea where is this behavior coming from?[/code]

[rawi]

What are the lower and upper limit of the integral? And what is the variable to integrate?

[Albert Chan]

(10-21-2022 08:35 PM)mmadurga Wrote:  I already had the solutionI calculated using a table of integrals so I could easily evaluate it in both HOME and CAS, and, lo and behold, I get 0.000E0 in HOME, 7.1054E-15 in CAS.

Since you use table of integrals, I assumed it has nothing to do with integration routine.

It may be due to massive cancellations, for F(hi) - F(lo)
HOME has 12 decimals precisions, but CAS has more (53-5 = 48-bits, or about 14+ decimals)