Not only can I reproduce this problem on my G4, running IDL 5.6 in OS
X 10.2.6, I can add some additional information that's quite
distressing.
I modified your code to give a little more output:
data0=fltarr(10000)+1.
for ii=0L, 10000L do begin $
data1=data0
;--- look for 0s
w0 = where(data1 EQ 0., count0)
if min(w0) GT 0 then begin
print, 'ii, count0 = ', ii, count0
print, ' w0 = ', w0, FORMAT='(a,99i9)'
print, ' data1(w0) = ', data1(w0), FORMAT='(a,99f9.4)'
print, ' '
endif
;--- look for not (1 or 0)
w1 = where((data1 NE 1.) AND (data1 NE 0.), count1)
if min(w1) GT 0 then begin
print, 'ii, count1 = ', ii, count1
print, ' w1 = ', w1, FORMAT='(a,99i9)'
print, ' data1(w1) = ', data1(w1), FORMAT='(a,99f9.4)'
print, ' '
endif
end
On a G4 733, the output was different every time the program was run,
but there is a striking predictability to the problem.
Here's the output of one test run
ii, count = 9187 8
w0 = 4076 4077 4078 4079 4080 4081
4082 4083
data1(w0) = 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
0.0000 0.0000
ii, count = 11494 8
w0 = 8172 8173 8174 8175 8176 8177
8178 8179
data1(w0) = 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
0.0000 0.0000
ii, count = 13739 8
w0 = 4076 4077 4078 4079 4080 4081
4082 4083
data1(w0) = 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
0.0000 0.0000
ii, count = 18309 8
w0 = 2028 2029 2030 2031 2032 2033
2034 2035
data1(w0) = 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
0.0000 0.0000
ii, count = 25220 8
w0 = 6124 6125 6126 6127 6128 6129
6130 6131
data1(w0) = 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
0.0000 0.0000
ii, count = 60714 8
w0 = 8172 8173 8174 8175 8176 8177
8178 8179
data1(w0) = 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
0.0000 0.0000
ii, count = 66317 8
w0 = 1004 1005 1006 1007 1008 1009
1010 1011
data1(w0) = 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
0.0000 0.0000
I noticed that there were usually strings of 8 zeros in a row (yet
sometimes just 2),
and that they corresponded most frequently to array index values 1004,
2028, 4076, 6124, 8172.
Those values happen to be 2^n - 20 where n=10,11,12, and 13. 6124 =
2^12 + 2^11 - 20.
The case where the numbers are neither zero nor one did not come up.
As designed, the test should produce no output whatsoever. On a P4
Linux machine I tested, there was no output.
This is terrible. Now what? I think the next step is to contact RSI
and see if they can duplicate the problem internally.
M. Katz
Rudi Sch�fer <rudi.schaefer@physik.uni-marburg.de> wrote in message news:<bh8393$2as$1@surz18.uni-marburg.de>...
> I recently discovered a very nasty problem on my G4 (2*867, Mac OS X
> 10.2.6) running IDL 5.6.
>
> The following code should not produce any output, if everything works.
> Unfortunately, this is not the case on my G4, where the variable
> assignment "data1=data0" produces messy data in a randomly fashion. So
> it works most of the time, but once in a while, the data in "data1" will
> be corrupted. Typically, there are some zeros showing up in the array
> and some other garbage.
>
> Here is the code in question:
>
> data0=fltarr(10000)+1.
> for ii=0L, 200000 do begin & $
> data1=data0 & $
> if min(where(data1 eq 0)) gt 0 then begin & $
> print, ii & ii=200001L & endif & $
> endfor
>
> This problem did not show up on other machines I have tested (Compaq
> Alpha, a Windows PC or my iMac G3 running the same OS and IDL versions).
>
> So this can either be a G4-specific bug in IDL 5.6, a G4-specific bug in
> Mac OS X 10.2.6, or a hardware problem on my G4.
>
> Since I do not have a second G4 available, I would like to ask anyone
> with a G4 to test the code snippet given above. You can simply paste the
> code to the command line in IDL.
>
> Thank you,
> Rudi
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