Function pfselftestCommand

src/hyperloglog.cpp:1399–1502

 * Something that is not easy to test from within the outside. */
#define HLL_TEST_CYCLES 1000
void pfselftestCommand(client *c) {
    unsigned int j, i;
    sds bitcounters = sdsnewlen(NULL,HLL_DENSE_SIZE);
    struct hllhdr *hdr = (struct hllhdr*) bitcounters, *hdr2;
    robj *o = NULL;
    uint8_t bytecounters[HLL_REGISTERS];
    int64_t checkpoint = 1;
    uint64_t seed = 0;
    uint64_t ele;
    double relerr = 0;

    /* Test 1: access registers.
     * The test is conceived to test that the different counters of our data
     * structure are accessible and that setting their values both result in
     * the correct value to be retained and not affect adjacent values. */
    for (j = 0; j < HLL_TEST_CYCLES; j++) {
        /* Set the HLL counters and an array of unsigned byes of the
         * same size to the same set of random values. */
        for (i = 0; i < HLL_REGISTERS; i++) {
            unsigned int r = rand() & HLL_REGISTER_MAX;

            bytecounters[i] = r;
            HLL_DENSE_SET_REGISTER(hdr->registers(),i,r);
        }
        /* Check that we are able to retrieve the same values. */
        for (i = 0; i < HLL_REGISTERS; i++) {
            unsigned int val;

            HLL_DENSE_GET_REGISTER(val,hdr->registers(),i);
            if (val != bytecounters[i]) {
                addReplyErrorFormat(c,
                    "TESTFAILED Register %d should be %d but is %d",
                    i, (int) bytecounters[i], (int) val);
                goto cleanup;
            }
        }
    }

    /* Test 2: approximation error.
     * The test adds unique elements and check that the estimated value
     * is always reasonable bounds.
     *
     * We check that the error is smaller than a few times than the expected
     * standard error, to make it very unlikely for the test to fail because
     * of a "bad" run.
     *
     * The test is performed with both dense and sparse HLLs at the same
     * time also verifying that the computed cardinality is the same. */
    memset(hdr->registers(),0,HLL_DENSE_SIZE-HLL_HDR_SIZE);
    o = createHLLObject();
    relerr = 1.04/sqrt(HLL_REGISTERS);
    checkpoint = 1;
    seed = (uint64_t)rand() | (uint64_t)rand() << 32;
    for (j = 1; j <= 10000000; j++) {
        ele = j ^ seed;
        hllDenseAdd(hdr->registers(),(unsigned char*)&ele,sizeof(ele));
        hllAdd(o,(unsigned char*)&ele,sizeof(ele));