Re: Manage a ROOT file from a streaming of the ROOT file content

> Hi Fons,
>
>> Hi Hassen,
>>
>> the HDFS plugin is readonly.
>
> Thanks for the clarification!
>
>> The idea is that you first copy the ROOT file onto HDFS and then
>> access if with ROOT.
>
> So it is possible to read directly (not through Fuse) a ROOT file
> stored onto HDFS. Please can you tell me the syntax? Here is for
> example an URI of a ROOT file in HDFS: hdfs://adminNode/user/hassen/
> file.root

Sorry for the spam! Seeing http://root.cern.ch/root/v526/Version526.news.html   , it seems that this syntax hdfs://adminNode/user/hassen/file.root did not work for us since we are using an old version of ROOT.

Between, If I understand, the HDFS plugin of ROOT allows just to bypass FUSE when reading from HDFS and not to read a ROOT file as an input stream. is it right? if it is the case, there is not a backup solution to TMemFile to read a root file as input stream? Since I expect that the usage of TMemFile in production will require an unreasonable amount of RAM.

Am I missing something?

Thanks for your help!
Hassen

>
> cheers
> Hassen
>
>>
>> Cheers, Fons.
>>
>> On 18/04/2012 09:44, Hassen Riahi wrote:
>>> Hi,
>>>
>>>> Hi,
>>>>
>>>> Another alternative is to try using the HDFS i/o plugin.
>>>
>>> Is there HDFS i/o plugin in ROOT? with which it is possible to write
>>> directly (not through Fuse) from ROOT to HDFS.
>>> If it is the case please point us to the documentation.
>>>
>>> cheers
>>> Hassen
>>>
>>>>
>>>> Cheers,
>>>> Philippe.
>>>>
>>>> On 4/17/12 10:29 AM, Massimiliano Fasi wrote:
>>>>> Hi all,
>>>>>
>>>>> In order to use Apache Hadoop with MapReduce streaming, we need
>>>>> a c++
>>>>> way to copy or cast a ROOT file passed through the standard
>>>>> input to any
>>>>> type of ROOT object (a TFile hopefully).
>>>>>
>>>>> Practically, we want to execute a command like
>>>>>
>>>>>> cat Myfile.root | MyAnalysisCode
>>>>>
>>>>> or
>>>>>
>>>>>> MyAnalysisCode < Myfile.root
>>>>>
>>>>> and then cast in MyAnalysisCode the standard input to something
>>>>> manageable by ROOT.
>>>>>
>>>>> Solutions we have tried so far didn't work. In particular, we
>>>>> tried to
>>>>> use the ifstream library but we wasn't able to cast their
>>>>> objects to
>>>>> something manageable by ROOT.
>>>>>
>>>>> Any hints or suggestions would be very appreciated.
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Massimiliano
>>>>>
>>>>> ----------------------------------------------------------------
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>>>>> Program.
>>>>>
>>>>>
>>>
>>
>> --
>> Org: CERN, European Laboratory for Particle Physics.
>> Mail: 1211 Geneve 23, Switzerland
>> E-Mail: Fons.Rademakers_at_cern.ch Phone: +41 22 7679248
>> WWW: http://fons.rademakers.org Fax: +41 22 7669640
>>
>
Received on Wed Apr 18 2012 - 13:21:39 CEST