Each work unit will be made into one or more identical tasks depending on the initial replication setting. Each of these tasks will be sent to a different computer. When the task on an individual computer is completed, the result of the computation will be uploaded. If more than one task was sent, the results will be compared in the validator.
Some applications can do a quick reverse computation to see if a result is valid or not, others require two results of the same computation to compare to each other. Unfortunately, individual computers cannot be trusted as they may overheat, be overclocked, have a random computation error, or (grumble) be maliciously modified so that credit accumulates faster. Hence the need for validation of computational results. SETI Classic had a handful of clients that were modified such that they would return pre-calculated results as quickly as the system would allow so that they would gain credits faster - thus potentially harming the science being done. This handful of clients returned a large number of invalid results. The same thing could happen in BOINC if there is no validation. -----Original Message----- From: boinc_dev [mailto:[email protected]] On Behalf Of Chanda Sarkar Sent: Thursday, June 20, 2013 7:42 AM To: Christian Beer Cc: [email protected] Subject: Re: [boinc_dev] Questions around BOINC Hi, Thanks for the information! But the URL that I read - http://boinc.berkeley.edu/trac/wiki/JobIn , says, in *JOB *section* - '*One or more *results*, each of which describes an instance of a computation, either unstarted, in progress, or completed. *The BOINC client software refers to results as "tasks"**'. *So, one work unit(job) may be associated with one or more results? More over what is the exact meaning of result file is it a single output file or a collection of output files that refers to single work unit. One more question that comes into my mind comes after reading - http://www.irelandboinc.com/how-boinc-works. Under Credit section - 'Each work unit may be sent to several computers' and 'When at least two results have been returned, the server compares them. If the results agree, then users are granted credits.'. According to this statement, same work unit(job) are sent to different machines for computation. So, does that mean same work unit(or job) may span multiple machines?.. which would contradict to the earlier mail. Do correct me if I am wrong Thanks, Chanda On Thu, Jun 20, 2013 at 2:36 PM, Christian Beer <[email protected]> wrote: > Hi, > > I'm not Rom but I hope I can help you too. > > 1. That scenario is already the principal design behind BOINC. Once a > task is associated with a host (gets send) this will not change. So in > your example: 't1' will only be processed on 'M1', if for some reason > this is not succesfull the server will create 't3' and send this to 'M3'. > > 2. What you see in your Screenshot is exact the behaviour I described > above. 't1' was created when the workunit (job) was created (because of > initial_replication=1) it got send to Computer 1619876 ('M1') on June 13 > later (on June 17) this computer reported that it has detached from the > project and discarded all remaining tasks. So the server created another > task ('t2') and it got send to 'M2' (1518828). This is also a normal > BOINC behaviour. If the first task is successfull there will be no > second task because the workunit is considered complete if one task is > succesfull (minimum_quorum=1). > > Regards > Christian > > Am 20.06.2013 10:53, schrieb Chanda Sarkar: > > Hi Rom, > > > > I have two questions around BOINC - > > > > 1. Is there any chance that single task within a work unit is > > processed only once on a single machine and no other machine. > > For example : > > Assume there is a work unit 'A' that has two tasks 't1' and 't2'. 't1' is > > send to machine 'M1' for processing and 't2' is send to machine 'M2' for > > processing. Is it a possibility that 't1' which is processed on machine > > 'M1' will never be processed for any other machine ? > > > > > > 2. Is there any possibility that task within a work unit may be > > generated with unpredictable time span which could be a day or more? I am > > attaching a snap shot for the same > > URL : http://screencast.com/t/HOvebaVpP0N > > In the above image it is seen for a work unit > > 'cryo_bk__chain_I_subrun_000_SAVE_ALL_OUT_IGNORE_THE_REST_86456_479' that > > has two tasks. One is created on 13th June 2013 and other on 17th June > > 2013. Is there a possibility that tasks within work units can be created > > with unpredictable time span? Please correct me if I am wrong. > > > > > > Thanks, > > Chanda > > _______________________________________________ > > boinc_dev mailing list > > [email protected] > > http://lists.ssl.berkeley.edu/mailman/listinfo/boinc_dev > > To unsubscribe, visit the above URL and > > (near bottom of page) enter your email address. > > _______________________________________________ boinc_dev mailing list [email protected] http://lists.ssl.berkeley.edu/mailman/listinfo/boinc_dev To unsubscribe, visit the above URL and (near bottom of page) enter your email address. _______________________________________________ boinc_dev mailing list [email protected] http://lists.ssl.berkeley.edu/mailman/listinfo/boinc_dev To unsubscribe, visit the above URL and (near bottom of page) enter your email address.
