Revision 35afde18 xseg/peers/user/bench-lfsr.c
| b/xseg/peers/user/bench-lfsr.c | ||
|---|---|---|
| 44 | 44 |
#include <sys/util.h> |
| 45 | 45 |
#include <signal.h> |
| 46 | 46 |
#include <bench-xseg.h> |
| 47 |
#include <limits.h> |
|
| 47 | 48 |
|
| 48 | 49 |
#include <math.h> |
| 49 | 50 |
|
| ... | ... | |
| 57 | 58 |
|
| 58 | 59 |
#define MAX_TAPS 6 |
| 59 | 60 |
|
| 61 |
#ifdef STAND_ALONE |
|
| 62 |
uint64_t global_seed; |
|
| 63 |
#endif |
|
| 64 |
|
|
| 60 | 65 |
/* |
| 61 | 66 |
* LFSRs are pseudo-random number generators. They are deterministic (meaning |
| 62 | 67 |
* that the same seed will produce the same number sequence) and extremely |
| ... | ... | |
| 188 | 193 |
* have (n+1) bits. |
| 189 | 194 |
* NOTE3: If an LFSR has n bits, the seed must not be all ones (= 2^(n+1) - 1) |
| 190 | 195 |
*/ |
| 196 |
/* |
|
| 191 | 197 |
int lfsr_init(struct lfsr *lfsr, uint64_t size, uint64_t seed) |
| 192 | 198 |
{
|
| 193 | 199 |
uint8_t i; |
| ... | ... | |
| 210 | 216 |
lfsr->state = seed; |
| 211 | 217 |
return 0; |
| 212 | 218 |
} |
| 219 |
*/ |
|
| 220 |
int lfsr_init(struct lfsr *lfsr, uint64_t size, uint64_t seed) |
|
| 221 |
{
|
|
| 222 |
uint8_t i; |
|
| 223 |
|
|
| 224 |
lfsr->limit = size; |
|
| 225 |
|
|
| 226 |
//i has number of bits of size |
|
| 227 |
for (i = 0; size; i++) |
|
| 228 |
size = size >> 1; |
|
| 213 | 229 |
|
| 230 |
//Too small or too big size to create an LFSR out of it |
|
| 231 |
if (i < 3 || i > 63) |
|
| 232 |
return -1; |
|
| 214 | 233 |
|
| 234 |
//The all ones state is illegal. Due to the fact that our seed is |
|
| 235 |
//nanoseconds taken from clock_gettime, we are sure that the 31st bit will |
|
| 236 |
//always be 0. The following codes has that in mind and creates a seed |
|
| 237 |
//that has at least one 0. |
|
| 238 |
if (seed == UINT64_MAX) {
|
|
| 239 |
if (i < 32) |
|
| 240 |
lfsr->state = global_seed >> (31 - i); |
|
| 241 |
else |
|
| 242 |
lfsr->state = global_seed << (i - 31); |
|
| 243 |
} |
|
| 244 |
else {
|
|
| 245 |
lfsr->state = seed; |
|
| 246 |
} |
|
| 247 |
|
|
| 248 |
lfsr->length = i; |
|
| 249 |
lfsr->xnormask = lfsr_create_xnormask(taps[i]); |
|
| 250 |
|
|
| 251 |
return 0; |
|
| 252 |
} |
|
| 253 |
|
|
| 254 |
#ifdef STAND_ALONE |
|
| 215 | 255 |
/* |
| 216 | 256 |
* Sanity-check every LFSR for wrong tap positions. |
| 217 | 257 |
*/ |
| ... | ... | |
| 249 | 289 |
return 0; |
| 250 | 290 |
} |
| 251 | 291 |
|
| 252 |
|
|
| 253 | 292 |
int main() |
| 254 | 293 |
{
|
| 255 | 294 |
int r; |
| ... | ... | |
| 258 | 297 |
|
| 259 | 298 |
return r; |
| 260 | 299 |
} |
| 300 |
#endif |
|
| 261 | 301 |
|
Also available in: Unified diff