[Maxima-bugs] [ maxima-Bugs-2452314 ] double quote integrate: inconsistent results

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Bugs item #2452314, was opened at 2008-12-20 01:03
Message generated for change (Comment added) made by crategus
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Category: None
Group: None
>Status: Closed
>Resolution: Works For Me
Priority: 5
Private: No
Submitted By: Ted Woollett (woollett)
Assigned to: Nobody/Anonymous (nobody)
Summary: double quote integrate: inconsistent results

Initial Comment:
inconsistent numerical results if I use
 two single quote integrate construct:

1. (bad results):  expand(float(''integrate(...)))

2. (good results):
 realpart(expand(float(''integrate(...))))

details:

assume(t>0)$
fS(t) := ''(integrate(sin(s^2*%pi/2),s,0,t))$
/* correct value for t = 1 */
realpart(expand(float(fS(1))));  --->  0.43825914739035

/* bad method 1: */
f1S(t):=expand(float(''( integrate (sin(s^2),s,0,t))))$

realpart(f1S(1));  --->  0.31026830172338
f1S(1);--->  0.31026830172338-9.8390953768041405E-17*%i

/* good method 2 */
f2S(t):= realpart(expand(
 float(''(integrate(sin(s^2*%pi/2),s,0,t)))))$

f2S(1);   --->  0.43825914739035

This looks strange.
Ted Woollett
woo...@ch...


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>Comment By: Dieter Kaiser (crategus)
Date: 2008-12-20 20:54

Message:
Closing the bug report.

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Comment By: Ted Woollett (woollett)
Date: 2008-12-20 19:32

Message:
Thanks, Dieter, for your clear eyes.
I need to pay more attention when
cutting and pasting!
Ted


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Comment By: Dieter Kaiser (crategus)
Date: 2008-12-20 14:51

Message:
As I can reproduce the examples all seems to be correct.

The numerical results differ because the integrands are different.

1.  fS(t)   -> the integrand is sin(s^2*%pi/2)
2.  f2S(t)  -> the integrand is sin(s^2)

If this is right the bug report can be closed.

Dieter Kaiser

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Comment By: Ted Woollett (woollett)
Date: 2008-12-20 01:52

Message:
build info
Maxima version: 5.17.1
Maxima build date: 19:10 12/18/2008
host type: i686-pc-mingw32
lisp-implementation-type: GNU Common Lisp (GCL)
lisp-implementation-version: GCL 2.6.8

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Comment By: Ted Woollett (woollett)
Date: 2008-12-20 01:21

Message:
same problem using verbify
(%i1) assume(t>0)$
(%i2) display2d:false$
(%i5) fS(t) := verbify(integrate)(sin(s^2 * %pi/2), s, 0, t)$
(%i6) realpart(expand(float(fS(1))));
(%o6) 0.43825914739035
(%i7) f1S(t):=expand(float(verbify(integrate)(sin(s^2),s,0,t)))$
(%i8) realpart(f1S(1));
(%o8) 0.31026830172338
(%i9) f2S(t):= realpart(expand(float
         (verbify(integrate)(sin(s^2*%pi/2),s,0,t))))$
(%i10) f2S(1);
(%o10) 0.43825914739035

Ted Woollett


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