## Usage ```javascript var randu = require( '@stdlib/random/base/randu' ); ``` #### randu() Returns a uniformly distributed pseudorandom number on the interval `[0,1)`. ```javascript var r = randu(); // returns ``` #### randu.factory( \[options] ) Returns a pseudorandom number generator (PRNG) for generating uniformly distributed random numbers on the interval `[0,1)`. ```javascript var rand = randu.factory(); ``` The function accepts the following `options`: - **name**: name of a supported pseudorandom number generator (PRNG), which will serve as the underlying source of pseudorandom numbers. The following generators are supported: - [`mt19937`][@stdlib/random/base/mt19937]: 32-bit Mersenne Twister. - [`minstd`][@stdlib/random/base/minstd]: linear congruential pseudorandom number generator (LCG) based on Park and Miller. - [`minstd-shuffle`][@stdlib/random/base/minstd-shuffle]: linear congruential pseudorandom number generator (LCG) whose output is shuffled. Default: [`'mt19937'`][@stdlib/random/base/mt19937]. - **seed**: pseudorandom number generator seed. Valid seed values vary according to the underlying PRNG. - **state**: pseudorandom number generator state. Valid state values vary according to the underlying PRNG. If provided, the function ignores the `seed` option. - **copy**: `boolean` indicating whether to copy a provided pseudorandom number generator state. Setting this option to `false` allows sharing state between two or more pseudorandom number generators. Setting this option to `true` ensures that a returned generator has exclusive control over its internal state. Default: `true`. By default, the underlying pseudorandom number generator is [`mt19937`][@stdlib/random/base/mt19937]. To use a different PRNG, set the `name` option. ```javascript var rand = randu.factory({ 'name': 'minstd-shuffle' }); var r = rand(); // returns ``` To seed a pseudorandom number generator, set the `seed` option. ```javascript var rand1 = randu.factory({ 'seed': 12345 }); var r1 = rand1(); // returns var rand2 = randu.factory({ 'seed': 12345 }); var r2 = rand2(); // returns var bool = ( r1 === r2 ); // returns true ``` To return a generator having a specific initial state, set the generator `state` option. ```javascript var rand; var bool; var r; var i; // Generate pseudorandom numbers, thus progressing the generator state: for ( i = 0; i < 1000; i++ ) { r = randu(); } // Create a new PRNG initialized to the current state of `randu`: rand = randu.factory({ 'state': randu.state }); // Test that the generated pseudorandom numbers are the same: bool = ( rand() === randu() ); // returns true ``` #### randu.NAME The generator name. ```javascript var str = randu.NAME; // returns 'randu' ``` #### randu.PRNG The underlying pseudorandom number generator. ```javascript var prng = randu.PRNG; // returns ``` #### randu.MIN Minimum value lower bound. ```javascript var min = randu.MIN; // returns 0.0 ``` #### randu.MAX Maximum value upper bound (not greater than `1` exclusive). ```javascript var max = randu.MAX; // returns ``` #### randu.seed The value used to seed `randu()`. ```javascript var rand; var r; var i; // Generate pseudorandom values... for ( i = 0; i < 100; i++ ) { r = randu(); } // Generate the same pseudorandom values... rand = randu.factory({ 'seed': randu.seed }); for ( i = 0; i < 100; i++ ) { r = rand(); } ``` #### randu.seedLength Length of generator seed. ```javascript var len = randu.seedLength; // returns ``` #### randu.state Writable property for getting and setting the generator state. ```javascript var r = randu(); // returns r = randu(); // returns // ... // Get a copy of the current state: var state = randu.state; r = randu(); // returns r = randu(); // returns // Reset the state: randu.state = state; // Replay the last two pseudorandom numbers: r = randu(); // returns r = randu(); // returns // ... ``` #### randu.stateLength Length of generator state. ```javascript var len = randu.stateLength; // returns ``` #### randu.byteLength Size (in bytes) of generator state. ```javascript var sz = randu.byteLength; // returns ``` #### randu.toJSON() Serializes the pseudorandom number generator as a JSON object. ```javascript var o = randu.toJSON(); // returns { 'type': 'PRNG', 'name': '...', 'state': {...}, 'params': [] } ```

## Notes - **Warning**: the default underlying source of pseudorandom numbers may **change** in the future. If exact reproducibility is required, either explicitly specify a PRNG via the `name` option or use an underlying PRNG directly. - If PRNG state is "shared" (meaning a state array was provided during PRNG creation and **not** copied) and one sets the generator state to a state array having a different length, the PRNG does **not** update the existing shared state and, instead, points to the newly provided state array. In order to synchronize PRNG output according to the new shared state array, the state array for **each** relevant PRNG must be **explicitly** set. - If PRNG state is "shared" and one sets the generator state to a state array of the same length, the PRNG state is updated (along with the state of all other PRNGs sharing the PRNG's state array).