// bend-blas, the JS twins: plain loops, correct and slow, for the
// interpreter and the tests. An Array<F32> is a JS array of numbers.
// A failure is io_fail(code): the runtime's message for a code is not
// this library's, so the code is the contract on this lane.
function bend_fresh(n) {
  let slots = 1;
  while (slots < n) slots *= 2;
  return new Array(slots).fill(0);
}
function bend_copy(src, n) {
  const c = bend_fresh(n);
  for (let i = 0; i < n; i++) c[i] = src[i];
  return c;
}
function bend_short(a, n) {
  return n > 0x7fffffff || a.length < n;
}
function bend_gemm(ta, tb, m, n, k, alpha, a, b, beta, c) {
  const out = bend_copy(c, m * n);
  for (let i = 0; i < m; i++) for (let j = 0; j < n; j++) {
    let acc = 0;
    for (let l = 0; l < k; l++) acc += (ta ? a[l * m + i] : a[i * k + l]) * (tb ? b[j * k + l] : b[l * n + j]);
    out[i * n + j] = alpha * acc + beta * out[i * n + j];
  }
  return out;
}
function lapack_sgesv(n, nrhs, a, b) {
  if (bend_short(a, n * n)) return io_fail(2);
  if (bend_short(b, n * nrhs)) return io_fail(2);
  const A = bend_copy(a, n * n), X = bend_copy(b, n * nrhs);
  for (let k = 0; k < n; k++) {
    let p = k;
    for (let i = k + 1; i < n; i++) if (Math.abs(A[i * n + k]) > Math.abs(A[p * n + k])) p = i;
    if (A[p * n + k] === 0) return io_fail(k + 1);
    if (p !== k) {
      for (let j = 0; j < n; j++) { const t = A[k * n + j]; A[k * n + j] = A[p * n + j]; A[p * n + j] = t; }
      for (let j = 0; j < nrhs; j++) { const t = X[k * nrhs + j]; X[k * nrhs + j] = X[p * nrhs + j]; X[p * nrhs + j] = t; }
    }
    for (let i = k + 1; i < n; i++) {
      const m = A[i * n + k] / A[k * n + k];
      for (let j = k; j < n; j++) A[i * n + j] -= m * A[k * n + j];
      for (let j = 0; j < nrhs; j++) X[i * nrhs + j] -= m * X[k * nrhs + j];
    }
  }
  for (let i = n - 1; i >= 0; i--) for (let j = 0; j < nrhs; j++) {
    let s = X[i * nrhs + j];
    for (let l = i + 1; l < n; l++) s -= A[i * n + l] * X[l * nrhs + j];
    X[i * nrhs + j] = s / A[i * n + i];
  }
  return io_done(X);
}
io_eff(CID(Lapack.sgesv), lapack_sgesv);