function job_finished($job, $inst, $user) {
    $response = null;
    if (get_str('submit', true)) {
        $response->have_ellipse = 0;
    } else {
        $response->have_ellipse = 1;
        $response->cx = get_int('pic_x');
        $response->cy = get_int('pic_y');
    }
    $inst->update_info($response);

    if ($job->calibration) {
        $b = $user->bossa;
        $info = $job->get_info();
        $answer = $info->answer;
        $u = $b->get_info();
        if (!$u) {
            $u->npos = 0;
            $u->npos_err = 0;
            $u->nneg = 0;
            $u->nneg_err = 0;
        }
        if (compatible($response, $answer)) {
            if ($answer->have_ellipse) {
                $u->npos++;
            } else {
                $u->nneg++;
            }
        } else {
            if ($answer->have_ellipse) {
                $u->npos++;
                $u->npos_err++;
            } else {
                $u->nneg++;
                $u->nneg_err++;
            }
        }
        $b->update_info($u);
        return;
    }

    // see if job is done
    //
    $insts = $job->get_finished_instances();
    $n = count($insts);

    $results = null;
    $users = null;
    foreach ($insts as $inst) {
        $results[] = $inst->get_info();
        $u = $inst->get_user();
        $users[] = $u->bossa->get_info();
    }

    // see if there's a negative consensus
    //
    $prob = 1;
    for ($i=0; $i<$n; $i++) {
        $r = $results[$i];
        if ($r1->have_ellipse) continue;
        $u = $users[$i];
        $prob *= $u->neg_err_rate;
    }
    if ($prob < PROB_LIMIT) {
        $job->update_state(BOSSA_JOB_DONE);
        return;
    }

    // see if there's a positive consensus
    //
    for ($i=0; $i<$n; $i++) {
        $r1 = $results[$i];
        $u = $users[$i];
        $prob = $u->pos_error_rate;
        for ($j=0; $j<$n; $j++) {
            if ($j == $i) continue;
            $r2 = $results[$j];
            if (compatible($r1, $r2)) {
                $u2 = $users[$j];
                $prob *= $u2->pos_err_rate;
            }
        }
        if ($prob < PROB_LIMIT) {
            $job->update_state(BOSSA_JOB_DONE);
            return;
        }
    }

    // see if there are too many instances without a consensus
    //
    if ($n >= 10) {
        $job->update_state(BOSSA_JOB_INCONCLUSIVE);
        return;
    }
}

function user_summary($user) {
    $b = $user->bossa;
    $info = $b->get_info();
    if ($info) {
        if ($info->npos) {
            $pos_err = $info->npos_err/$info->npos;
        } else {
            $pos_err = "---";
        }
        if ($info->nneg) {
            $neg_err = $info->nneg_err/$info->nneg;
        } else {
            $neg_err = "---";
        }
        return "error rate: positive $pos_err ($info->npos_err/$info->npos),
             negative $neg_err ($info->nneg_err/$info->nneg)
        ";
    } else {
        return "No data";
    }
}