# BNNSRandomGeneratorSetState(_:_:_:) Sets the state of a random number generator. ``` func BNNSRandomGeneratorSetState(_ generator: BNNSRandomGenerator?, _ state_size: Int, _ state: UnsafeMutableRawPointer) -> Int32 ``` ## Parameters `generator` The random number generator. `state_size` The size of the state buffer, in bytes. `state` A pointer to the state. ## Discussion Use the [`BNNSRandomGeneratorGetState(_:_:_:)`](/documentation/Accelerate/BNNSRandomGeneratorGetState(_:_:_:)) and [`BNNSRandomGeneratorSetState(_:_:_:)`](/documentation/Accelerate/BNNSRandomGeneratorSetState(_:_:_:)) functions to capture and restore a random number generator’s state. The following code creates a random number generator and captures its initial state. The code calls [`BNNSRandomFillUniformInt(_:_:_:_:)`](/documentation/Accelerate/BNNSRandomFillUniformInt(_:_:_:_:)) twice and copies the random values into the arrays `a` and `b`. The [`BNNSRandomGeneratorSetState(_:_:_:)`](/documentation/Accelerate/BNNSRandomGeneratorSetState(_:_:_:)) function restores the generator to its initial state, and the final call to [`BNNSRandomFillUniformInt(_:_:_:_:)`](/documentation/Accelerate/BNNSRandomFillUniformInt(_:_:_:_:)) populates the descriptor so that the values in arrays `a` and `c` are equal. ```swift let data = UnsafeMutableBufferPointer.allocate(capacity: 8) var descriptor = BNNSNDArrayDescriptor(flags: BNNSNDArrayFlags(0), layout: BNNSDataLayoutVector, size: (10, 0, 0, 0, 0, 0, 0, 0), stride: (0, 0, 0, 0, 0, 0, 0, 0), data: data.baseAddress!, data_type: BNNSDataType.int16, table_data: nil, table_data_type: BNNSDataType.int16, data_scale: 1, data_bias: 0) guard let randomNumberGenerator = BNNSCreateRandomGenerator(BNNSRandomGeneratorMethodAES_CTR, nil) else { return } // Allocate memory to store state. let stateSize = BNNSRandomGeneratorStateSize(randomNumberGenerator) let state = UnsafeMutableRawPointer.allocate(byteCount: stateSize, alignment: 0) // Store the random number generator's state. BNNSRandomGeneratorGetState(randomNumberGenerator, stateSize, state) BNNSRandomFillUniformInt(randomNumberGenerator, &descriptor, -10, 10) let a = Array(data) BNNSRandomFillUniformInt(randomNumberGenerator, &descriptor, -10, 10) let b = Array(data) // Set the random number generator's state to its initial state. BNNSRandomGeneratorSetState(randomNumberGenerator, stateSize, state) BNNSRandomFillUniformInt(randomNumberGenerator, &descriptor, -10, 10) let c = Array(data) print(a.elementsEqual(c)) // prints "true" data.deallocate() state.deallocate() BNNSDestroyRandomGenerator(randomNumberGenerator) ``` --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)