| Re: Maximum index for arrays? [message #62559] |
Mon, 15 September 2008 06:38 |
pgrigis
Messages: 436
Registered: September 2007
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Senior Member |
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hotplainrice@gmail.com wrote:
> Hi guys,
>
> Thanks for helping me for the past few weeks. I've managed to get
> CUBLAS and other CUDA programs working in IDL. What I have now for you
> guys is this.
>
> Here is the code
>
> N = 181
> N2 = N^2
> a = fltarr(N2, 141)
> help,a
>
> A FLOAT = Array[32761, 141]
>
> N = 182
> N2 = N^2
> a = fltarr(N2, 141)
> % Array dimensions must be greater than 0
> % Execution halted at: TEST 5 /home/hpr/test.pro
> % $MAIN$
> IDL>
>
> How big can the index go? Its because I need N = 100 to 1000
Just for the records, IDL 32-bit can have arrays with a maximum of
about
2^31/N elements, where N is the size in byte of one element (i.e. 1
for bytes,
2 for int, 4 for long int and floats, etc. etc.).
On the orther hand, IDL 64 bits can (in principle) allocate arrays so
large that you won't be able to store them anyway (at least for the
next
few years or so)
Cheers,
Paolo
>
> Regards
> Zaki
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| Re: Maximum index for arrays? [message #62562 is a reply to message #62559] |
Mon, 15 September 2008 03:15  |
hotplainrice@gmail.co
Messages: 15
Registered: July 2008
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Junior Member |
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On Sep 15, 6:53 pm, Chris <beaum...@ifa.hawaii.edu> wrote:
> On Sep 14, 8:08 pm, "hotplainr...@gmail.com" <hotplainr...@gmail.com>
> wrote:
>
>
>
>> Hi guys,
>
>> Thanks for helping me for the past few weeks. I've managed to get
>> CUBLAS and other CUDA programs working in IDL. What I have now for you
>> guys is this.
>
>> Here is the code
>
>> N = 181
>> N2 = N^2
>> a = fltarr(N2, 141)
>> help,a
>
>> A FLOAT = Array[32761, 141]
>
>> N = 182
>> N2 = N^2
>> a = fltarr(N2, 141)
>> % Array dimensions must be greater than 0
>> % Execution halted at: TEST 5 /home/hpr/test.pro
>> % $MAIN$
>> IDL>
>
>> How big can the index go? Its because I need N = 100 to 1000
>
>> Regards
>> Zaki
>
> The problem is that the line
> N = 182
> sets N to a 16-bit signed integer (max size 32767-ish). When you
> square it (33124), it overflows and becomes negative (-32412). Use
> something like
> N=182L (long integer with max size about 2 billion) or
> N=2. (floating point)
>
> As long as you have the RAM, arrays can have millions or billions (i
> think) of elements, so you'll be fine.
>
> chris
Thanks chris, that resolved the problem.
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| Re: Maximum index for arrays? [message #62565 is a reply to message #62562] |
Mon, 15 September 2008 01:53 |
Chris[6]
Messages: 84
Registered: July 2008
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Member |
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On Sep 14, 8:08 pm, "hotplainr...@gmail.com" <hotplainr...@gmail.com>
wrote:
> Hi guys,
>
> Thanks for helping me for the past few weeks. I've managed to get
> CUBLAS and other CUDA programs working in IDL. What I have now for you
> guys is this.
>
> Here is the code
>
> N = 181
> N2 = N^2
> a = fltarr(N2, 141)
> help,a
>
> A FLOAT = Array[32761, 141]
>
> N = 182
> N2 = N^2
> a = fltarr(N2, 141)
> % Array dimensions must be greater than 0
> % Execution halted at: TEST 5 /home/hpr/test.pro
> % $MAIN$
> IDL>
>
> How big can the index go? Its because I need N = 100 to 1000
>
> Regards
> Zaki
The problem is that the line
N = 182
sets N to a 16-bit signed integer (max size 32767-ish). When you
square it (33124), it overflows and becomes negative (-32412). Use
something like
N=182L (long integer with max size about 2 billion) or
N=2. (floating point)
As long as you have the RAM, arrays can have millions or billions (i
think) of elements, so you'll be fine.
chris
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