<random>: piecewise_linear_distribution is still broken

[statementreply]

Describe the bug

piecewise_linear_distribution doesn't produce the correct random number distribution.

Command-line test case

G:\Temp>type devcom_421634.cpp
#include <cstdio>
#include <iterator>
#include <random>

using namespace std;

int main() {
    constexpr double intervals[] = {0, 1, 5};
    constexpr double weights[]   = {0, 1, 0};
    constexpr double x           = 2;
    constexpr double probability = 0.55;
    constexpr int total          = 1'000'000;

    piecewise_linear_distribution<> distribution(begin(intervals), end(intervals), begin(weights));
    mt19937 generator;

    int count = 0;
    for (int i = 0; i < total; ++i) {
        if (distribution(generator) < x) {
            ++count;
        }
    }

    const double frequency = static_cast<double>(count) / total;

    printf("Expected probability = %f\n", probability);
    printf("Actual frequency     = %f (%d / %d)\n", frequency, count, total);
}

G:\Temp>cl /EHsc /W4 /WX devcom_421634.cpp
用于 x64 的 Microsoft (R) C/C++ 优化编译器 19.26.28806 版
版权所有(C) Microsoft Corporation。保留所有权利。

devcom_421634.cpp
Microsoft (R) Incremental Linker Version 14.26.28806.0
Copyright (C) Microsoft Corporation.  All rights reserved.

/out:devcom_421634.exe
devcom_421634.obj

G:\Temp>.\devcom_421634.exe
Expected probability = 0.550000
Actual frequency     = 0.718845 (718845 / 1000000)

STL version

Microsoft Visual Studio Community 2019
版本 16.6.3

Additional context

Also tracked on Developer Community as DevCom-421634 and by Microsoft-internal VSO-115939 / AB#115939.

[StephanTLavavej]

Thanks, I've linked the Microsoft-internal bug to this issue.