geohash encode/decode performance compare

gistfile1.txt

Code:
int main()
{
    GeoHashBits hash, fast_hash;
    GeoHashNeighbors neighbors;

    GeoHashRange lat_range, lon_range;
    lat_range.max = 20037726.37;
    lat_range.min = -20037726.37;
    lon_range.max = 20037726.37;
    lon_range.min = -20037726.37;
    double radius = 5000;
    double latitude = 9741705.20;
    double longitude = 5417390.90;

    uint32_t loop = 10000000;
    uint32_t i = 0;
    uint64_t start = get_current_epoch_millis();
    for (i = 0; i < loop; i++)
    {
        geohash_encode(lat_range, lon_range, latitude, longitude, 24, &hash);
    }
    uint64_t end = get_current_epoch_millis();
    printf("Cost %llums to encode\n", end - start);

    start = get_current_epoch_millis();
    for (i = 0; i < loop; i++)
    {
        geohash_fast_encode(lat_range, lon_range, latitude, longitude, 24, &fast_hash);
    }
    end = get_current_epoch_millis();
    printf("Cost %llums to fast encode\n", end - start);

    GeoHashArea area, area1;
    start = get_current_epoch_millis();
    for (i = 0; i < loop; i++)
    {
        geohash_decode(lat_range, lon_range, hash, &area);
    }
    end = get_current_epoch_millis();
    printf("Cost %llums to decode\n", end - start);

    start = get_current_epoch_millis();
    for (i = 0; i < loop; i++)
    {
        geohash_fast_decode(lat_range, lon_range, hash, &area1);
    }
    end = get_current_epoch_millis();
    printf("Cost %llums to fast decode\n", end - start);

    return 0;
}

Run at same machine with different version compiler, different optimize flag
gcc 4.8.2  linux 2.6.32 
compile with -O2
Cost 1912ms to encode
Cost 445ms to fast encode
Cost 1948ms to decode
Cost 927ms to fast decode

compile with -O0
Cost 3628ms to encode
Cost 716ms to fast encode
Cost 6475ms to decode
Cost 949ms to fast decode

gcc 3.4.5 linux 2.6.32 
compile with -O2
Cost 2935ms to encode
Cost 526ms to fast encode
Cost 1823ms to decode
Cost 1937ms to fast decode         //slower

compile with -O0
Cost 6964ms to encode
Cost 1245ms to fast encode
Cost 10288ms to decode
Cost 2740ms to fast decode


Update: use simple divide/shift operations instead of math function 'ldexp'
gcc 4.8.2  linux 2.6.32 
compile with -O2
Cost 1235ms to encode
Cost 282ms to fast encode
Cost 1236ms to  decode
Cost 195ms to fast decode

compile with -O0
Cost 3653ms to encode
Cost 719ms to fast encode
Cost 6486ms to  decode
Cost 620ms to fast decode

gcc 3.4.5 linux 2.6.32 
compile with -O2
Cost 2950ms to encode
Cost 546ms to fast encode
Cost 2101ms to  decode
Cost 400ms to fast decode

compile with -O0
Cost 6984ms to encode
Cost 1241ms to fast encode
Cost 10555ms to  decode
Cost 1495ms to fast decode

gcc 3.4.5 is also 9 years old, so newer compilers probably have better optimizations.

Unfortunately in my working company, gcc 3.4.5 is widely used, most application compiled by it.