Changes between Version 16 and Version 17 of ValidationIntro

Timestamp:

Mar 20, 2014, 12:23:27 PM (10 years ago)

Author:

davea

Comment:

--

ValidationIntro

@@ -1 +1 @@
 = Validation =
 
-In BOINC, a '''validator''' is a program that decides whether results are correct.
-You must supply a validator for each application in your project,
+A '''validator''' is a program that decides whether completed jobs are "valid".
+You must specify a validator for each application in your project,
 and include it in the <daemons> section of your [ProjectConfigFile project configuration file].
 
-Depending on various factors, you may be able to use a standard validator that comes with BOINC,
-or you may have to develop a custom validator.
+Validating a completed job has 2 parts:
+ * '''Syntax check''': verify that its output files are present on the server
+  and have the correct format.
+ * '''Replication check''': if the job is [JobReplication replicated], compare its replicas.
+ If a strict majority are found to be "equivalent",
+ those replicas are considered valid and the rest are marked as invalid.
 
- * If your application generates exactly matching results
-  (either because it does no floating-point arithmetic,
-  or because you use [HomogeneousRedundancy homogeneous redundancy])
-  then you can use the 'sample bitwise validator' (see below).
- * If you are using BOINC for 'desktop grid' computing
-  (i.e. you trust all the participating hosts) then you can use the 'sample trivial validator' (see below).
- * Otherwise, you'll need to [ValidationSimple develop a custom validator] for your application.
+Validators grant credit for valid results.
+By default, this uses the mechanism described [CreditNew here].
+There are several [CreditAlt alternative ways of granting credit].
 
-Several standard validators are supplied:
+BOINC includes several "standard" validators:
+ '''sample_trivial_validator'''::
+   Marks a job as valid if its output files are present.
+   Use this if all hosts are trusted.
+   Not used with job replication.
+ '''sample_substr_validator'''::
+   Marks a job as valid if its stderr output includes a string
+   specified by the --stderr_substr command-line arg.
+   Not used with job replication.
+ '''sample_bitwise_validator'''::
+   Output files are equivalent if they agree byte for byte.
+   This can be used if your application generates exactly matching results
+   (either because it does no floating-point arithmetic,
+   or because you use [HomogeneousRedundancy homogeneous redundancy]).
+   If output files are gzip archives, use the '''--is_gzip''' command-line arg.
+   This will skip the gzip header when comparing files.
 
- * The '''sample_bitwise_validator''' requires a strict majority, and regards results as equivalent only if they agree byte for byte.
- * The '''sample_trivial_validator''' accepts all results as valid.
- * The '''sample_substr_validator''' accepts results whose stderr output includes a string specified by the --stderr_substr command-line arg.
-
-By default, a validator grants credit for valid results using a default mechanism (described [CreditNew here]).
-There are several [CreditAlt alternative ways of granting credit].
+For a given application,
+you may want to define your own syntax check for output files,
+or your own notion of "equivalence"
+(for example, regarding floating-point numbers as equivalent if they agree within some tolerance).
+In such cases, you can [ValidationSimple develop a custom validator] for the application.
 
 === Command-line arguments ===