Tutorial by Examples: p

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POSIX thread library provides implementation of the mutex primitive, used for the mutual exclusion. Mutex is created using pthread_mutex_init, and destroyed using pthread_mutex_destroy. Obtaining a mutex can be done using pthread_mutex_lock or pthread_mutex_trylock, (depending if the timeout is desi...

The command :g/apples/y A will yank all lines containing the word apples into the a register, which can be pasted with "ap. Any regular expression can be used. Note the space before the A, and the capitalization of the register letter. If a capital letter is used as the yank register, matc...

pmap takes a function (that you specify) and applies it to all of the elements in an array. This work is divided up amongst the available workers. pmap then returns places the results from that function into another array. addprocs(3) sqrts = pmap(sqrt, 1:10) if you function takes multiple ar...

@parallel can be used to parallellize a loop, dividing steps of the loop up over different workers. As a very simple example: addprocs(3) a = collect(1:10) for idx = 1:10 println(a[idx]) end For a slightly more complex example, consider: @time begin @sync begin @paral...

The macros @spawn and @spawnat are two of the tools that Julia makes available to assign tasks to workers. Here is an example: julia> @spawnat 2 println("hello world") RemoteRef{Channel{Any}}(2,1,3) julia> From worker 2: hello world Both of these macros will evaluate an ex...

The Julia documentation advises that pmap() is designed for the case where each function call does a large amount of work. In contrast, @parallel for can handle situations where each iteration is tiny, perhaps merely summing two numbers. There are several reasons for this. First, pmap incurs ...

Stored procedures can return values using the OUTPUT keyword in its parameter list. Creating a stored procedure with a single out parameter CREATE PROCEDURE SprocWithOutParams ( @InParam VARCHAR(30), @OutParam VARCHAR(30) OUTPUT ) AS BEGIN SELECT @OutParam = @InParam + ' must co...

One might want to GROUP BY more than one column declare @temp table(age int, name varchar(15)) insert into @temp select 18, 'matt' union all select 21, 'matt' union all select 21, 'matt' union all select 18, 'luke' union all select 18, 'luke' union all select 21, 'luke' union all select 1...

-- Identity primary key - unique arbitrary increment number create table person ( id int identity(1,1) primary key not null, firstName varchar(100) not null, lastName varchar(100) not null, dob DateTime not null, ssn varchar(9) not null )

-- GUID primary key - arbitrary unique value for table create table person ( id uniqueIdentifier default (newId()) primary key, firstName varchar(100) not null, lastName varchar(100) not null, dob DateTime not null, ssn varchar(9) not null )

-- composite key - using two or more existing columns within a table to create a primary key create table person ( firstName varchar(100) not null, lastName varchar(100) not null, dob DateTime not null, ssn varchar(9) not null, primary key (firstName, lastName, dob) )

ALTER TABLE person ADD CONSTRAINT pk_PersonSSN PRIMARY KEY (ssn) Note, if the primary key column (in this case ssn) has more than one row with the same candidate key, the above statement will fail, as primary key values must be unique.

ALTER TABLE Person DROP CONSTRAINT pk_PersonSSN

The simplest way is to use the Activator class. However, even though Activator performance have been improved since .NET 3.5, using Activator.CreateInstance() is bad option sometimes, due to (relatively) low performance: Test 1, Test 2, Test 3... With Activator class Type type = typeof(BigInteg...

AppDomain.UnhandledException This event provides notification of uncaught exceptions.It allows the application to log information about the exception before the system default handler reports the exception to the user and terminates the application.If sufficient information about the state of the a...

There are several to evaluate a certain expression when debugging a Java application. 1. Manually inspecting an expression When the program execution is suspended at a certain line (either due to a breakpoint or manually stepping through the debugger), you can manually evaluate an expression by se...

n order to debug a remote Java application, it should be launched with some extra arguments to instruct the JVM to execute it in debug mode. This is done as follows: java -Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=8000 -jar sampleApp.jar The above command tells the JVM to s...

To do this you need a reference to the assembly which contains the type. If you have another type available which you know is in the same assembly as the one you want you can do this: typeof(KnownType).Assembly.GetType(typeName); where typeName is the name of the type you are looking for (incl...

Extension methods can be used to "hide" processing of inelegant business rules that would otherwise require cluttering up a calling function with if/then statements. This is similar to and analogous to handling nulls with extension methods. For example, public static class CakeExtensions ...