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Merge pull request #556 from Knogle/fibonacci
Implemented Lagged Fibonacci generator PRNG providing high-speed, medium-quality numbers.
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,79 @@ | ||
| /* | ||
| * Additive Lagged Fibonacci Generator (ALFG) Implementation | ||
| * Author: Fabian Druschke | ||
| * Date: 2024-03-13 | ||
| * | ||
| * This is an implementation of the Additive Lagged Fibonacci Generator (ALFG), | ||
| * a pseudorandom number generator known for its simplicity and good statistical properties | ||
| * for a wide range of applications. ALFGs are particularly noted for their long periods | ||
| * and efficiency in generating sequences of random numbers. However, like many other PRNGs, | ||
| * they are not suitable for cryptographic purposes due to their predictability. | ||
| * | ||
| * As the author of this implementation, I, Fabian Druschke, hereby release this work into | ||
| * the public domain. I dedicate any and all copyright interest in this work to the public | ||
| * domain, making it free to use for anyone for any purpose without any conditions, unless | ||
| * such conditions are required by law. | ||
| * | ||
| * This software is provided "as is", without warranty of any kind, express or implied, | ||
| * including but not limited to the warranties of merchantability, fitness for a particular | ||
| * purpose, and noninfringement. In no event shall the authors be liable for any claim, | ||
| * damages, or other liability, whether in an action of contract, tort, or otherwise, arising | ||
| * from, out of, or in connection with the software or the use or other dealings in the software. | ||
| * | ||
| * Note: This implementation is designed for non-cryptographic applications and should not be | ||
| * used where cryptographic security is required. | ||
| */ | ||
|
|
||
| #include "add_lagg_fibonacci_prng.h" | ||
| #include <stdint.h> | ||
| #include <string.h> | ||
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| #define STATE_SIZE 64 // Size of the state array, sufficient for a high period | ||
| #define LAG_BIG 55 // Large lag, e.g., 55 | ||
| #define LAG_SMALL 24 // Small lag, e.g., 24 | ||
| #define MODULUS ( 1ULL << 48 ) // Modulus for the operations, here 2^48 for simple handling | ||
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| void add_lagg_fibonacci_init( add_lagg_fibonacci_state_t* state, uint64_t init_key[], unsigned long key_length ) | ||
| { | ||
| // Simple initialization: Fill the state with the key values and then with a linear combination of them | ||
| for( unsigned long i = 0; i < STATE_SIZE; i++ ) | ||
| { | ||
| if( i < key_length ) | ||
| { | ||
| state->s[i] = init_key[i]; | ||
| } | ||
| else | ||
| { | ||
| // Simple method to generate further state values. Should be improved for serious applications. | ||
| state->s[i] = ( 6364136223846793005ULL * state->s[i - 1] + 1 ) % MODULUS; | ||
| } | ||
| } | ||
| state->index = 0; // Initialize the index for the first generation | ||
| } | ||
|
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| void add_lagg_fibonacci_genrand_uint256_to_buf( add_lagg_fibonacci_state_t* state, unsigned char* bufpos ) | ||
| { | ||
| uint64_t* buf_as_uint64 = (uint64_t*) bufpos; // Interprets bufpos as a uint64_t array for direct assignment | ||
| int64_t result; // Use signed integer to handle potential negative results from subtraction | ||
|
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| for (int i = 0; i < 4; i++) { | ||
| // Subtract the two previous numbers in the sequence | ||
| result = (int64_t)state->s[(state->index + LAG_BIG) % STATE_SIZE] - (int64_t)state->s[(state->index + LAG_SMALL) % STATE_SIZE]; | ||
|
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| // Handle borrow if result is negative | ||
| if (result < 0) { | ||
| result += MODULUS; | ||
| // Optionally set a borrow flag or adjust the next operation based on borrow logic | ||
| } | ||
|
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| // Store the result (after adjustment) back into the state, ensuring it's positive and within range | ||
| state->s[state->index] = (uint64_t)result; | ||
|
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| // Write the result into buf_as_uint64 | ||
| buf_as_uint64[i] = state->s[state->index]; | ||
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| // Update the index for the next round | ||
| state->index = (state->index + 1) % STATE_SIZE; | ||
| } | ||
| } | ||
|
|
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,43 @@ | ||
| /* | ||
| * Additive Lagged Fibonacci Generator (ALFG) Implementation definitions | ||
| * Author: Fabian Druschke | ||
| * Date: 2024-03-13 | ||
| * | ||
| * This is an implementation of the Additive Lagged Fibonacci Generator (ALFG), | ||
| * a pseudorandom number generator known for its simplicity and good statistical properties | ||
| * for a wide range of applications. ALFGs are particularly noted for their long periods | ||
| * and efficiency in generating sequences of random numbers. However, like many other PRNGs, | ||
| * they are not suitable for cryptographic purposes due to their predictability. | ||
| * | ||
| * As the author of this implementation, I, Fabian Druschke, hereby release this work into | ||
| * the public domain. I dedicate any and all copyright interest in this work to the public | ||
| * domain, making it free to use for anyone for any purpose without any conditions, unless | ||
| * such conditions are required by law. | ||
| * | ||
| * This software is provided "as is", without warranty of any kind, express or implied, | ||
| * including but not limited to the warranties of merchantability, fitness for a particular | ||
| * purpose, and noninfringement. In no event shall the authors be liable for any claim, | ||
| * damages, or other liability, whether in an action of contract, tort, or otherwise, arising | ||
| * from, out of, or in connection with the software or the use or other dealings in the software. | ||
| * | ||
| * Note: This implementation is designed for non-cryptographic applications and should not be | ||
| * used where cryptographic security is required. | ||
| */ | ||
|
|
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| #ifndef ADD_LAGG_FIBONACCI_PRNG_H | ||
| #define ADD_LAGG_FIBONACCI_PRNG_H | ||
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| #include <stdint.h> | ||
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| // State definition for the Additive Lagged Fibonacci Generator | ||
| typedef struct | ||
| { | ||
| uint64_t s[64]; // State array | ||
| unsigned int index; // Current index in the state array | ||
| } add_lagg_fibonacci_state_t; | ||
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| // Function prototypes | ||
| void add_lagg_fibonacci_init( add_lagg_fibonacci_state_t* state, uint64_t init_key[], unsigned long key_length ); | ||
| void add_lagg_fibonacci_genrand_uint256_to_buf( add_lagg_fibonacci_state_t* state, unsigned char* bufpos ); | ||
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| #endif // ADD_LAGG_FIBONACCI_PRNG_H |
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