195 lines
5.7 KiB
C++
195 lines
5.7 KiB
C++
///////////////////////////////////////////////////////////////////////////
|
|
//
|
|
// Copyright (c) 2002-2012, Industrial Light & Magic, a division of Lucas
|
|
// Digital Ltd. LLC
|
|
//
|
|
// All rights reserved.
|
|
//
|
|
// Redistribution and use in source and binary forms, with or without
|
|
// modification, are permitted provided that the following conditions are
|
|
// met:
|
|
// * Redistributions of source code must retain the above copyright
|
|
// notice, this list of conditions and the following disclaimer.
|
|
// * Redistributions in binary form must reproduce the above
|
|
// copyright notice, this list of conditions and the following disclaimer
|
|
// in the documentation and/or other materials provided with the
|
|
// distribution.
|
|
// * Neither the name of Industrial Light & Magic nor the names of
|
|
// its contributors may be used to endorse or promote products derived
|
|
// from this software without specific prior written permission.
|
|
//
|
|
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
|
|
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
|
|
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
|
|
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
|
|
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
|
|
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
|
|
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
|
|
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
|
|
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
|
|
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
|
|
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
//
|
|
///////////////////////////////////////////////////////////////////////////
|
|
|
|
//-----------------------------------------------------------------------------
|
|
//
|
|
// Routines that generate pseudo-random numbers compatible
|
|
// with the standard erand48(), nrand48(), etc. functions.
|
|
//
|
|
//-----------------------------------------------------------------------------
|
|
|
|
#include "ImathRandom.h"
|
|
#include "ImathInt64.h"
|
|
|
|
IMATH_INTERNAL_NAMESPACE_SOURCE_ENTER
|
|
namespace {
|
|
|
|
//
|
|
// Static state used by Imath::drand48(), Imath::lrand48() and Imath::srand48()
|
|
//
|
|
|
|
unsigned short staticState[3] = {0, 0, 0};
|
|
|
|
|
|
void
|
|
rand48Next (unsigned short state[3])
|
|
{
|
|
//
|
|
// drand48() and friends are all based on a linear congruential
|
|
// sequence,
|
|
//
|
|
// x[n+1] = (a * x[n] + c) % m,
|
|
//
|
|
// where a and c are as specified below, and m == (1 << 48)
|
|
//
|
|
|
|
static const Int64 a = Int64 (0x5deece66dLL);
|
|
static const Int64 c = Int64 (0xbLL);
|
|
|
|
//
|
|
// Assemble the 48-bit value x[n] from the
|
|
// three 16-bit values stored in state.
|
|
//
|
|
|
|
Int64 x = (Int64 (state[2]) << 32) |
|
|
(Int64 (state[1]) << 16) |
|
|
Int64 (state[0]);
|
|
|
|
//
|
|
// Compute x[n+1], except for the "modulo m" part.
|
|
//
|
|
|
|
x = a * x + c;
|
|
|
|
//
|
|
// Disassemble the 48 least significant bits of x[n+1] into
|
|
// three 16-bit values. Discard the 16 most significant bits;
|
|
// this takes care of the "modulo m" operation.
|
|
//
|
|
// We assume that sizeof (unsigned short) == 2.
|
|
//
|
|
|
|
state[2] = (unsigned short)(x >> 32);
|
|
state[1] = (unsigned short)(x >> 16);
|
|
state[0] = (unsigned short)(x);
|
|
}
|
|
|
|
} // namespace
|
|
|
|
|
|
double
|
|
erand48 (unsigned short state[3])
|
|
{
|
|
//
|
|
// Generate double-precision floating-point values between 0.0 and 1.0:
|
|
//
|
|
// The exponent is set to 0x3ff, which indicates a value greater
|
|
// than or equal to 1.0, and less than 2.0. The 48 most significant
|
|
// bits of the significand (mantissa) are filled with pseudo-random
|
|
// bits generated by rand48Next(). The remaining 4 bits are a copy
|
|
// of the 4 most significant bits of the significand. This results
|
|
// in bit patterns between 0x3ff0000000000000 and 0x3fffffffffffffff,
|
|
// which correspond to uniformly distributed floating-point values
|
|
// between 1.0 and 1.99999999999999978. Subtracting 1.0 from those
|
|
// values produces numbers between 0.0 and 0.99999999999999978, that
|
|
// is, between 0.0 and 1.0-DBL_EPSILON.
|
|
//
|
|
|
|
rand48Next (state);
|
|
|
|
union {double d; Int64 i;} u;
|
|
|
|
u.i = (Int64 (0x3ff) << 52) | // sign and exponent
|
|
(Int64 (state[2]) << 36) | // significand
|
|
(Int64 (state[1]) << 20) |
|
|
(Int64 (state[0]) << 4) |
|
|
(Int64 (state[2]) >> 12);
|
|
|
|
return u.d - 1;
|
|
}
|
|
|
|
|
|
double
|
|
drand48 ()
|
|
{
|
|
return IMATH_INTERNAL_NAMESPACE::erand48 (staticState);
|
|
}
|
|
|
|
|
|
long int
|
|
nrand48 (unsigned short state[3])
|
|
{
|
|
//
|
|
// Generate uniformly distributed integers between 0 and 0x7fffffff.
|
|
//
|
|
|
|
rand48Next (state);
|
|
|
|
return ((long int) (state[2]) << 15) |
|
|
((long int) (state[1]) >> 1);
|
|
}
|
|
|
|
|
|
long int
|
|
lrand48 ()
|
|
{
|
|
return IMATH_INTERNAL_NAMESPACE::nrand48 (staticState);
|
|
}
|
|
|
|
|
|
void
|
|
srand48 (long int seed)
|
|
{
|
|
staticState[2] = (unsigned short)(seed >> 16);
|
|
staticState[1] = (unsigned short)(seed);
|
|
staticState[0] = 0x330e;
|
|
}
|
|
|
|
|
|
float
|
|
Rand32::nextf ()
|
|
{
|
|
//
|
|
// Generate single-precision floating-point values between 0.0 and 1.0:
|
|
//
|
|
// The exponent is set to 0x7f, which indicates a value greater than
|
|
// or equal to 1.0, and less than 2.0. The 23 bits of the significand
|
|
// (mantissa) are filled with pseudo-random bits generated by
|
|
// Rand32::next(). This results in in bit patterns between 0x3f800000
|
|
// and 0x3fffffff, which correspond to uniformly distributed floating-
|
|
// point values between 1.0 and 1.99999988. Subtracting 1.0 from
|
|
// those values produces numbers between 0.0 and 0.99999988, that is,
|
|
// between 0.0 and 1.0-FLT_EPSILON.
|
|
//
|
|
|
|
next ();
|
|
|
|
union {float f; unsigned int i;} u;
|
|
|
|
u.i = 0x3f800000 | (_state & 0x7fffff);
|
|
return u.f - 1;
|
|
}
|
|
|
|
IMATH_INTERNAL_NAMESPACE_SOURCE_EXIT
|