[commit-cp] [bugs #11058] ARM double to ascii conversion issue

[Ingo Proetel]

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 of the project: classpath.

/**************************************************************************/
[bugs #11058] Latest Modifications:

Changes by: 
                Ingo Proetel <address@hidden>
'Date: 
                Thu 12/02/2004 at 07:42 (GMT)

------------------ Additional Follow-up Comments ----------------------------
We have seen somthing similar before. The problem for us was that doubles in 
tha Java class are stored as big endian. And the conversion did not correctly 
take into account that the arm has what we call a cross-endianess (i.e the 
dwords are exchanged). 

You could check if the bits differ when you store a float value in the class 
file and if you let it compute at run-time.






/**************************************************************************/
[bugs #11058] Full Item Snapshot:

URL: <http://savannah.gnu.org/bugs/?func=detailitem&item_id=11058>
Project: classpath
Submitted by: 0
On: Fri 11/19/2004 at 17:56

Category:  classpath
Severity:  5 - Average
Resolution:  None
Privacy:  Public
Assigned to:  None
Status:  Open
Platform Version:  None


Summary:  ARM double to ascii conversion issue

Original Submission:  Hi,

  I've cross compiled CLASSPATH on an S3C2410 ARM920 architecture. I've also 
compiled SableVM on it.
When I run this code :
    float a = 1.5f;
    float b = 26.524f;
    float c = 1.11E11f;
    float d = a + b;
    int   e = (int)d;
  
    System.Out.println("a is "+a);
    System.Out.println("b is "+b);
    System.Out.println("d is "+d);
    System.Out.println("e is "+e);

I get wrong result for float (and double, I've tried them too) output (the 
output is totally garbaged), but the number show as e is correct. 
I think the problem seem to be in _dtoa function in fdlibm.

ARM are very strict on memory alignment, and is little endian.

PS: The same code works on x86.

Output is (This is the input => a=1.5f,b=26.524f,c=1.11E11f):
----------
float test
----------
a=1.000007
b=37.63494
c=1.1100000256E11
(int)a =1
(int)b =26
(int)c =2147483647
a+b=39.034943
a+c=1.1100000256E11
a-b=-36.034943
a-c=-1.1100000256E11
(int)(a+b)=28
(int)(a+c)=2147483647
(int)(a-b)=-25
(int)(a-c)=-2147483648
a*b=4:.89693;
a*c=1.66500007936E11
a/b=0.02
a/c=28.7935:8
(int)(a*b)=39
(int)(a*c)=2147483647
(int)(a/b)=0
(int)(a/c)=17



Follow-up Comments
------------------


-------------------------------------------------------
Date: Thu 12/02/2004 at 07:42       By: Ingo Proetel <iproetel>
We have seen somthing similar before. The problem for us was that doubles in 
tha Java class are stored as big endian. And the conversion did not correctly 
take into account that the arm has what we call a cross-endianess (i.e the 
dwords are exchanged). 

You could check if the bits differ when you store a float value in the class 
file and if you let it compute at run-time.

-------------------------------------------------------
Date: Wed 12/01/2004 at 11:43       By: 0 <None>
Okay, this could explain why double are not converted correctly. However float 
are on a single DWORD, hence it should work with float (which, I guess, are 
corrects)

However, even with float _dtoa doesn't work. Is there a _ftoa method ?

Thanks

-------------------------------------------------------
Date: Mon 11/29/2004 at 14:55       By: Sven de Marothy <smarothy>
Well.. looking at your values here, it seems like the top and bottom dwords of 
the Double are getting exchanged, and that the top one is getting set to zero. 

This could be due to dword ordering, or alignment or both. In any case, I'm not 
entirely sure the problem is in the Double->ASCII conversion alone. It could be 
that the SableVM double-arithmetic on this architecture is broken. Or both 
could be broken. 



-------------------------------------------------------
Date: Wed 11/24/2004 at 11:39       By: 0 <None>
the test class:
---------------

import java.io.*;

public class Cos {

public static double div(double a, double b){
return a/b;
}

public static void main(String[] args){
double a = Math.cos(Math.PI);
double b = -1.0;
System.out.println("a equals b:"+(a == b));
System.out.println("a:"+a);
System.out.println("b:"+b); 
System.out.println("Double.doubleToLongBits(a):"+Double.doubleToLongBits(a));
System.out.println("Double.doubleToLongBits(a):"+Double.doubleToLongBits(a));
System.out.println("Double.doubleToRawLongBits(b):"+Double.doubleToRawLongBits(b));
System.out.println("Double.doubleToRawLongBits(b):"+Double.doubleToRawLongBits(b));
System.out.println("Float.floatToRawIntBits((float)a):"+Float.floatToRawIntBits((float)a));
System.out.println("Float.floatToIntBits((float)a):"+Float.floatToIntBits((float)a));
System.out.println("Float.floatToRawIntBits((float)b):"+Float.floatToRawIntBits((float)b));
System.out.println("Float.floatToIntBits((float)b):"+Float.floatToIntBits((float)b));
a = 1.002;
b = 0.;
System.out.println("a div b:" + div(a,b));
System.out.println("a:"+a);
System.out.println("b:"+b); 
System.out.println("Double.doubleToLongBits(a):"+Double.doubleToLongBits(a));
System.out.println("Double.doubleToLongBits(a):"+Double.doubleToLongBits(a));
System.out.println("Double.doubleToRawLongBits(b):"+Double.doubleToRawLongBits(b));
System.out.println("Double.doubleToRawLongBits(b):"+Double.doubleToRawLongBits(b));
System.out.println("Float.floatToRawIntBits((float)a):"+Float.floatToRawIntBits((float)a));
System.out.println("Float.floatToIntBits((float)a):"+Float.floatToIntBits((float)a));
System.out.println("Float.floatToRawIntBits((float)b):"+Float.floatToRawIntBits((float)b));
System.out.println("Float.floatToIntBits((float)b):"+Float.floatToIntBits((float)b));
a = 8.8888888E21;
b = 5.5555555E-21;
System.out.println("a:"+a);
System.out.println("b:"+b);
System.out.println("Double.doubleToLongBits(a):"+Double.doubleToLongBits(a));
System.out.println("Double.doubleToLongBits(a):"+Double.doubleToLongBits(a));
System.out.println("Double.doubleToRawLongBits(b):"+Double.doubleToRawLongBits(b));
System.out.println("Double.doubleToRawLongBits(b):"+Double.doubleToRawLongBits(b));
System.out.println("Float.floatToRawIntBits((float)a):"+Float.floatToRawIntBits((float)a));
System.out.println("Float.floatToIntBits((float)a):"+Float.floatToIntBits((float)a));
System.out.println("Float.floatToRawIntBits((float)b):"+Float.floatToRawIntBits((float)b));
System.out.println("Float.floatToIntBits((float)b):"+Float.floatToIntBits((float)b));

}
}

Result :
--------

a equals b:true
a:-1.0
b:-1.0
Double.doubleToLongBits(a):3220176896
Double.doubleToLongBits(a):3220176896
Double.doubleToRawLongBits(b):3220176896
Double.doubleToRawLongBits(b):3220176896
Float.floatToRawIntBits((float)a):-1082130432
Float.floatToIntBits((float)a):-1082130432
Float.floatToRawIntBits((float)b):-1082130432
Float.floatToIntBits((float)b):-1082130432
a div b:Infinity
a:2.002:958353678385
b:0.0
Double.doubleToLongBits(a):1072695345
Double.doubleToLongBits(a):1072695345
Double.doubleToRawLongBits(b):0
Double.doubleToRawLongBits(b):0
Float.floatToRawIntBits((float)a):1065369993
Float.floatToIntBits((float)a):1065369993
Float.floatToRawIntBits((float)b):0
Float.floatToIntBits((float)b):0
a:0.0000000000026E21
b:Q.0E-21
Double.doubleToLongBits(a):1149115873
Double.doubleToLongBits(a):1149115873
Double.doubleToRawLongBits(b):1002060865
Double.doubleToRawLongBits(b):1002060865
Float.floatToRawIntBits((float)a):1676734222
Float.floatToIntBits((float)a):1676734222
Float.floatToRawIntBits((float)b):500294153
Float.floatToIntBits((float)b):500294153

----------
I hope this will be helpful !

-------------------------------------------------------
Date: Tue 11/23/2004 at 06:40       By: Sven de Marothy <smarothy>
Thanks for the follow-up. Strange. Looks like you're right that this seems to 
be in dtoa.c, and not a general fdlibm thing. Could you provide output of 
Float.floatToRawIntBits() and Double.doubleToRawLongBits() for the different 
input/output values? This would be helpful.



-------------------------------------------------------
Date: Mon 11/22/2004 at 13:40       By: 0 <None>
Tested your class, and I've added some other tests too.
/ Below is Java File /
import java.io.*;
 
public class Cos {
 
   public static double div(double a, double b){
    return a/b;
   }
 
   public static void main(String[] args){
       double a = Math.cos(Math.PI);
       double b = -1.0;
       System.out.println("a equals b:"+(a == b));
       System.out.println("a:"+a);
       System.out.println("b:"+b);       
       a = 1.002;
       b = 0.;
       System.out.println("a div b:" + div(a,b));
       System.out.println("a:"+a);
       System.out.println("b:"+b);       
    a = 8.8888888E21;
       b = 5.5555555E-21;
       System.out.println("a:"+a);
       System.out.println("b:"+b);
 
   }
}

/ And this is the output /
a equals b:true
a:-1.0
b:-1.0
a div b:Infinity
a:2.002:958353678385
b:0.0
a:0.0000000000026E21
b:Q.0E-21

-------------------------------------------------------
Date: Mon 11/22/2004 at 09:18       By: Sven de Marothy <smarothy>
I'm not entirely sure if this is a general fdlibm problem, or specific to dtoa. 
Could you test this? 

I've attached a little test-case which might be an indicator,  checking the 
output of a fdlibm function with the expected value.

-------------------------------------------------------
Date: Mon 11/22/2004 at 08:57       By: Michael Koch <mkoch>
This was originally reported to http://sablevm.org/bugs/74

-------------------------------------------------------
Date: Fri 11/19/2004 at 22:53       By: Sven de Marothy <smarothy>
Unfortunately, most of us don't have an ARM machine to test this on. 

However, looking at the fdlibm code, there's #ifdefs for ARM in ieeefp.h, and 
some more in atoi.c (Pack_32?) so it could be a build issue. I'd try playing 
around with the #ifdefs.

If you find something, please post it here and let us know!







File Attachments
-------------------

-------------------------------------------------------
Date: Mon 11/22/2004 at 09:18  Name: Cos.java  Size: 278B   By: smarothy
Test
http://savannah.gnu.org/bugs/download.php?item_id=11058&amp;item_file_id=1902






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