The thread pool code used in the Java backend was tied the execution of
main/2. However if Mercury is used as a library the thread pool won't have
been started and threads created with thread.spawn would not be executed.
This patch makes it possible to start and stop the thread pool independently of
main/2 by calling startup() and shutdown(). These calls are called
implicitly by calling runMain(). The thread pool can also be started on
demand.
This patch also adds the MercuryRuntime class, which now contains methods
that may be called by users' Java code to interact with the Mercury runtime
system, including a new finalise() method.
java/runtime/MercuryThreadPool.java:
Add startup() method.
shutdown() method is now public and it's meaning has changed, it now
requests the shutdown rather than performing it.
Renamed some variables to make their meanings clearer.
java/runtime/JavaInternal.java:
Initialise the ThreadPool and MercuryOptions objects on demand.
Make all members of this class static to avoid confusion.
Add a private constructor.
java/runtime/MercuryRuntime.java:
Add methods that can be called by Mercury users to interact with the
runtime system. Including a convenient finalise() method that does all
the finalisation.
samples/java_interface/standalone_java/mercury_lib.m:
samples/java_interface/standalone_java/JavaMain.java:
Extend the standalone Java example so that it makes use of threads: Add
a fibs function in Mercury that uses concurrency and therefore starts
the thread pool; call it from the Java code.
Use the new finalise() method from the MercuryRuntime class inside of a
finally block.
samples/java_interface/standalone_java/Makefile:
Fix a minor error.
Thread pools are often used to reduce poor performance on embarrassingly
parallel work loads. This isn't immediately necessary on the Java backend
however I've implemented it because:
+ It will be required when we implement parallel conjunctions for the
Java backend.
+ I want to implement parallel profiling on the Java backend and don't
want to have to implement this once now, and then re-implement it after
introducing thread pools later.
We want the thread pool to generally restrict the number of threads that are
in use, this reduces overheads. However, when one or more tasks become
blocked then it can be desirable to create extra threads, this helps ensure
that all processors are kept busy and that thread pooling doesn't contribute
to any deadlocks itself. The implementation is a work in prograss and
currently does not implement this second feature.
Java's API provides several different thread pools, see
java.util.concurrent.Executors, none of which are suitable. Specifically
the fixed thread pool is unsuitable as we want to be able to temporarily
exceed the normal number of threads as explained above; and the cached
thread pools, which are also very similar to the ThreadPoolExecutor class,
do not implement the correct algorithm for determining when a new thread
should be created (they can still perform poorly for embarassingly parallel
workloads). Additionally we cannot instrument this code as easily for
parallel profiling.
These changes alter the behaviour of Mercury threads on the Java backend in
two ways, they now behave more correctly and more like threads on the C
backends.
+ If a thread throws an exception it is now reported and the program is
aborted. Previously it was ignored and let pass to the Java runtime
where I assume it was reported.
+ The program now exits only after all threads have exited.
The ThreadPool will automatically detect the number of threads to use, or if
the -P flag is given in the MERCURY_OPTIONS environment variable it will
honor that.
java/runtime/MercuryThread.java:
java/runtime/MercuryThreadPool.java:
java/runtime/MercuryWorkerThread.java:
java/runtime/Task.java:
java/runtime/ThreadStatus.java:
These new classes make up the thread pool. A MercuryThread is an
abstract class for Mercury threads, MercuryWorkerThread is a concrete
subclass of MercuryThread which includes the worker thread behaviour.
A Task is a computation/closure that has not yet been started, it
provides some methods not available in Java's generic Runnable and
Callable classes. The others should be self-explanatory and all files
contain documentation.
java/runtime/Getopt.java:
java/runtime/MercuryOptions.java:
Parse the MERCURY_OPTIONS environment variable for the -P flag.
java/runtime/JavaInternal.java:
Add support for handling Mercury exceptions, this is used in case a
worker thread's task (a Mercury thread) throws an exception.
compiler/mlds_to_java.m:
The main method of the main Java class of an application now starts and
uses the thread pool to execute main/2.
library/exception.m:
Export exception reporting code to the Java runtime system.
library/thread.m:
Use the thread pool for thread.spawn.
Branches: main
compiler/make_hlds_passes.m:
Support `thread_local' mutables on Java backend.
Add some newlines in generated code for mutables.
compiler/prog_mutable.m:
Update documentation.
java/runtime/JavaInternal.java:
Avoid a warning.
Branches: main
Make `:- initialise' and `:- finalise' declarations work in Java grades.
Initialisation predicates are simply called from static initialisation blocks.
Finalisation predicates work by registering methods (objects) with the
JavaInternal runtime class. After main/2 terminates each of the registered
methods is called.
compiler/make_hlds_passes.m:
Make add_pass_3_initialise, add_pass_3_finalise generate predicates
for backends other than C.
compiler/mlds_to_java.m:
Generate code to register finalisation predicates with the runtime.
Make the generated code that calls main/2 call run the registered
finalisers as well.
java/runtime/JavaInternal.java:
Add code to register and call finalisers when main/2 terminates.
Branches: main
Put all Mercury-generated Java classes into the package `jmercury' and
runtime classes into `jmercury.runtime'. The Mercury module hierarchy is
not reflected in the package name. We name sub-module classes using
their fully-qualified module names with `__' between components, e.g.
`bit_buffer.read' produces `class bit_buffer__read'.
As all generated Java code is in the same package we don't need to package
qualify identifiers, and we don't need the hack to avoid clashing package
and class names. It also makes it easier to write Java foreign code because
generated Java class names are easier to predict from Mercury module names.
The package names are not `mercury' and `mercury.runtime' because on
case-insensitive file systems we may end up with a `mercury' directory
that could be confused with the `Mercury' directory.
compiler/java_names.m:
Delete code related to mangling package names.
Remove the extra `mercury' prefix added to standard library module
names, as it is redundant with `jmercury'.
Change runtime package name.
compiler/mlds_to_java.m:
Make generated code follow the new packaging scheme.
Don't automatically import all runtime classes. It doesn't seem
necessary.
Update for new packaging scheme.
compiler/file_names.m:
Fix Java file paths for the new packaging scheme.
compiler/module_cmds.m:
compiler/rtti.m:
library/array.m:
library/backjump.m:
library/benchmarking.m:
library/bitmap.m:
library/builtin.m:
library/exception.m:
library/io.m:
library/library.m:
library/mutvar.m:
library/private_builtin.m:
library/rtti_implementation.m:
library/store.m:
library/string.m:
library/time.m:
library/type_desc.m:
java/runtime/*.java:
Rename package names.
Delete unnecessary package qualification.
compiler/mlds.m:
Add some XXXs to be fixed later.
library/Mmakefile:
Update for new packaging scheme.
Let mmake --use-mmc-make work in this directory.
Estimated hours taken: 3
Branches: main
Added support for progname and exit status in grade Java.
compiler/mlds_to_java.m:
Added code to maybe_write_main_driver/5 to store the main class's name
and exit status in mercury.runtime.JavaInternal's static variables.
Also, main() now calls java.lang.System.exit() instead of returning,
since Java insists that main must have void return type.
java/runtime/JavaInternal.java:
Added static variables "progname" and "exit_status".
Estimated hours taken: 3
Branches: main
This change introduces some (partial) Java versions of the mercury library
which are currently needed to compile some .java files generated by the
mercury compiler for the tests/benchmarks test cases.
These additions are required temporarily for testing purposes until the
mercury library can be compiled in grade java.
mercury/java/Commit.java:
mercury/java/DuExistInfo.java:
mercury/java/DuExistLocn.java:
mercury/java/DuFunctorDesc.java:
mercury/java/DuPtagLayout.java:
mercury/java/EnumFunctorDesc.java:
mercury/java/JavaInternal.java:
mercury/java/MethodPtr.java:
mercury/java/NotagFunctorDesc.java:
mercury/java/PseudoTypeInfo.java:
mercury/java/Sectag_Locn.java:
mercury/java/TypeCtorInfo_Struct.java:
mercury/java/TypeCtorRep.java:
mercury/java/TypeFunctors.java:
mercury/java/TypeLayout.java:
mercury/java/UnreachableDefault.java:
All files that were located in the mercury/java directory have been
moved to mercury/java/runtime.
mercury/java/Makefile:
A simple Makefile to set up a couple of symbolic links so we can
just include the mercury/java directory in our CLASSPATH.
mercury/java/library/assoc_list.java:
mercury/java/library/bool.java:
mercury/java/library/builtin.java:
mercury/java/library/deconstruct.java:
mercury/java/library/enum.java:
mercury/java/library/integer.java:
mercury/java/library/io.java:
mercury/java/library/list.java:
mercury/java/library/map.java:
mercury/java/library/mer_int.java:
mercury/java/library/mr_char.java:
mercury/java/library/mr_float.java:
mercury/java/library/mr_int.java:
mercury/java/library/ops.java:
mercury/java/library/private_builtin.java:
mercury/java/library/require.java:
mercury/java/library/set.java:
mercury/java/library/std_util.java:
mercury/java/library/string.java:
mercury/java/library/term.java:
mercury/java/library/time.java:
mercury/java/library/tree234.java:
mercury/java/library/type_desc.java:
These are partial Java versions of mercury library modules. They are
very rough but will currently allow for most of the tests/benchmark
directory to run in Java.
