josh/j3ml
1
0
Fork 1
Code Issues 12 Pull Requests Actions Packages Projects Releases 41 Wiki Activity

RNG class has bug in Float(), sort it out soon

Browse Source
This commit is contained in:
josh
2024-06-04 16:24:30 -04:00
parent ab6b2b7972
commit c17ed20fa9
2 changed files with 11 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
include/J3ML/Algorithm/RNG.h
View File

@@ -4,7 +4,7 @@
namespace J3ML::Algorithm
{
/** @brief A linear congruential random number generator.
/** @brief A linear congruential random number generator.
Uses D.H. Lehmer's Linear Congruential Method (1949) for generating random numbers.
Supports both Multiplicative Congruential Method (increment==0) and

19
src/J3ML/Algorithm/RNG.cpp
View File

@@ -39,17 +39,17 @@ namespace J3ML::Algorithm {
assert(modulus != 0);
/// TODO: Convert to using Shrage's method for approximate factorization (Numerical Recipes in C)
// Currently we cast everything to 65-bit to avoid overflow, which is quite dumb.
// Currently we cast everything to 64-bit to avoid overflow, which is quite dumb.
// Creates the new random number
u64 newNum = ((u64)lastNumber * (u64)multiplier + (u64)increment % (u64)modulus);
//u64 newNum = ((u64)lastNumber * (u64)multiplier + (u64)increment % (u64)modulus);
// TODO: use this on console platforms to rely on smaller sequences.
// u32 m = lastNumber * multiplier;
// u32 i = m + increment;
// u32 f = i & 0x7FFFFFFF;
// u32 m = (lastNumber * 214013 + 2531011) & 0x7FFFFFFF;
// unsigned __int64 newNum = (lastNumber * multiplier + increment) & 0x7FFFFFFF;
u32 m = lastNumber * multiplier;
u32 i = m + increment;
u32 f = i & 0x7FFFFFFF;
//u32 m = (lastNumber * 214013 + 2531011) & 0x7FFFFFFF;
u64 newNum = (lastNumber * multiplier + increment) & 0x7FFFFFFF;
assert( ((u32)newNum!=0 || increment != 0) && "RNG degenerated to producing a stream of zeroes!");
lastNumber = (u32)newNum;
return lastNumber;
@@ -89,8 +89,9 @@ namespace J3ML::Algorithm {
float RNG::Float() {
u32 i = ((u32)Int() & 0x007FFFFF /* random mantissa */) | 0x3F800000 /* fixed exponent */;
auto f = ReinterpretAs<float, u32>(i); // f is now in range [1, 2[
f -= 1.f; // Map to range [0, 1[
// TODO: PROPERLY fix this.
auto f = (float)i / 1e31; //ReinterpretAs<float, u32>(i); // f is now in range [1, 2[
//f -= 1.f; // Map to range [0, 1[
assert(f >= 0.f);
assert(f < 1.f);
return f;