rnd.wnext(long long n, int w) is broken when w <= -25

[alex65536]

The number distribution in rnd.wnext(long long n, int w) seems to be broken for negative w when it exceeds random_t::lim; (currently equal to 25). For positive w, and for rnd.wnext(int n, int w) the bug isn't reproducible.

To reproduce the bug, compile and run the following code (C++14):

#include "testlib.h"
#include <vector>
#include <iostream>
#include <algorithm>

using namespace std;

inline void distribution(int n, int m, int w) {
	vector< pair<int, int> > knt(n);
	for (int i = 0; i < n; i++) {
		knt[i].second = i;
	}
	for (int i = 0; i < m; i++) {
		knt[rnd.wnext((int64_t)n, w)].first++;
	}
	sort(knt.begin(), knt.end());
	reverse(knt.begin(), knt.end());
	cout << "n = " << n << " m = " << m << " w = " << w << "\n";
	cout << "Distribution in top-5:\n";
	for (int i = 0; i < 5 && i < n; i++) {
		cout << knt[i].first << " " << knt[i].second << "\n";
	}
	cout << "----\n";
	cout << endl;
}

int main(int argc, char **argv) {
	registerGen(argc, argv, 1);
	distribution(100'000, 200'000, +24);
	distribution(100'000, 200'000, +25);
	distribution(100'000, 200'000, -24);
	distribution(100'000, 200'000, -25);
	return 0;
}

The output is:

n = 100000 m = 200000 w = 24
Distribution in top-5:
65 99971
65 99786
65 99389
64 99942
64 99613
----

n = 100000 m = 200000 w = 25
Distribution in top-5:
74 99694
69 99672
67 99942
66 99949
66 99839
----

n = 100000 m = 200000 w = -24
Distribution in top-5:
72 53
67 531
67 112
67 70
67 11
----

n = 100000 m = 200000 w = -25
Distribution in top-5:
128235 0
3558 1
2065 2
1426 3
1129 4
----

As you can see, the results for w=-25 greatly differ from others.

[yhx-12243]

Compare the implementation of the function wnext's, maybe the 1 - and the 1.0 / is forgotten.
(the implementation of wnext(int, int) is right, but the implementation of wnext(long long, int) and wnext(double, int) has a few bugs.)

testlib/testlib.h

Lines 809 to 818 in b288e8e

	{
	double p;
	if (type > 0)
	p = std::pow(next() + 0.0, 1.0 / (type + 1));
	else
	p = 1 - std::pow(next() + 0.0, 1.0 / (-type + 1));
	return int(n * p);
	}

testlib/testlib.h

Lines 840 to 849 in b288e8e

	{
	double p;
	if (type > 0)
	p = std::pow(next() + 0.0, 1.0 / (type + 1));
	else
	p = std::pow(next() + 0.0, - type + 1);
	return __testlib_min(__testlib_max((long long)(double(n) * p), 0LL), n - 1LL);
	}