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Use local algorithm for random, bug1332.

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This commit is contained in:
Wilson Snyder 2018-08-26 07:07:01 -04:00
parent 573e79a329
commit 77f6b8cf5f
3 changed files with 40 additions and 30 deletions
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@ -11,6 +11,8 @@ The contributors that suggested a given feature are shown in []. Thanks!
** Add runtime arguments.
** Note $random has new algorithm; results may vary vs. previous versions.
*** Better optimize large always block splitting, bug1244. [John Coiner]
*** Add new reloop optimization for repetitive assignment compression.

66
include/verilated.cpp
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@ -209,27 +209,12 @@ Verilated::NonSerialized::~NonSerialized() {
}
//===========================================================================
// Random reset -- Only called at init time, so don't inline.
// Random -- Mostly called at init time, so not inline.
IData VL_RAND32() VL_MT_SAFE {
#ifdef VL_THREADED
static VL_THREAD_LOCAL bool t_seeded = false;
static VL_THREAD_LOCAL drand48_data t_buffer;
static VerilatedMutex s_mutex;
if (VL_UNLIKELY(!t_seeded)) {
t_seeded = true;
long seedval;
{
VerilatedLockGuard lock(s_mutex);
seedval = lrand48()<<16 ^ lrand48();
if (!seedval) seedval++;
}
srand48_r(seedval, &t_buffer);
}
long v0; lrand48_r(&t_buffer, &v0);
long v1; lrand48_r(&t_buffer, &v1);
return (v0<<16) ^ v1;
#elif defined(_WIN32) && !defined(__CYGWIN__)
static vluint32_t vl_sys_rand32() VL_MT_UNSAFE {
// Return random 32-bits using system library.
// Used only to construct seed for Verilator's PNRG.
#if defined(_WIN32) && !defined(__CYGWIN__)
// Windows doesn't have lrand48(), although Cygwin does.
return (rand()<<16) ^ rand();
#else
@ -237,21 +222,46 @@ IData VL_RAND32() VL_MT_SAFE {
#endif
}
vluint64_t vl_rand64() VL_MT_SAFE {
static VerilatedMutex s_mutex;
static VL_THREAD_LOCAL bool t_seeded = false;
static VL_THREAD_LOCAL vluint64_t t_state[2];
if (VL_UNLIKELY(!t_seeded)) {
t_seeded = true;
{
long seedval;
VerilatedLockGuard lock(s_mutex);
t_state[0] = (((vluint64_t)vl_sys_rand32())<<32
^ ((vluint64_t)vl_sys_rand32()));
t_state[1] = (((vluint64_t)vl_sys_rand32())<<32
^ ((vluint64_t)vl_sys_rand32()));
// Fix state as algorithm is slow to randomize if many zeros
// This causes a loss of ~ 1 bit of seed entropy, no big deal
if (VL_COUNTONES_I(t_state[0]) < 10) t_state[0] = ~t_state[0];
if (VL_COUNTONES_I(t_state[1]) < 10) t_state[1] = ~t_state[1];
}
}
// Xoroshiro128+ algorithm
vluint64_t result = t_state[0] + t_state[1];
t_state[1] ^= t_state[0];
t_state[0] = (((t_state[0] << 55) | (t_state[0] >> 9))
^ t_state[1] ^ (t_state[1] << 14));
t_state[1] = (t_state[1] << 36) | (t_state[1] >> 28);
return result;
}
IData VL_RANDOM_I(int obits) VL_MT_SAFE {
return VL_RAND32() & VL_MASK_I(obits);
return vl_rand64() & VL_MASK_I(obits);
}
QData VL_RANDOM_Q(int obits) VL_MT_SAFE {
QData data = ((QData)VL_RAND32()<<VL_ULL(32)) | (QData)VL_RAND32();
return data & VL_MASK_Q(obits);
return vl_rand64() & VL_MASK_Q(obits);
}
WDataOutP VL_RANDOM_W(int obits, WDataOutP outwp) VL_MT_SAFE {
for (int i=0; i<VL_WORDS_I(obits); ++i) {
if (i<(VL_WORDS_I(obits)-1)) {
outwp[i] = VL_RAND32();
outwp[i] = vl_rand64();
} else {
outwp[i] = VL_RAND32() & VL_MASK_I(obits);
outwp[i] = vl_rand64() & VL_MASK_I(obits);
}
}
return outwp;
@ -266,7 +276,6 @@ IData VL_RAND_RESET_I(int obits) VL_MT_SAFE {
if (obits<32) data &= VL_MASK_I(obits);
return data;
}
QData VL_RAND_RESET_Q(int obits) VL_MT_SAFE {
if (Verilated::randReset()==0) return 0;
QData data = VL_ULL(~0);
@ -276,7 +285,6 @@ QData VL_RAND_RESET_Q(int obits) VL_MT_SAFE {
if (obits<64) data &= VL_MASK_Q(obits);
return data;
}
WDataOutP VL_RAND_RESET_W(int obits, WDataOutP outwp) VL_MT_SAFE {
for (int i=0; i<VL_WORDS_I(obits); ++i) {
if (i<(VL_WORDS_I(obits)-1)) {

2
include/verilated_threads.h
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@ -205,7 +205,7 @@ public:
return 0;
#endif
}
};
class VlThreadPool;