datetime.secs vs secsf vs double. int64_t vs double

bench-datetime-secs.lua

local ffi = require('ffi')
local clock = require('clock')
local builtin = ffi.C

local datetime_t = ffi.typeof('struct datetime')
local SECS_PER_DAY     = 86400
local DT_EPOCH_1970_OFFSET = 719163LL

ffi.cdef [[
struct datetime_double {
	/** seconds since epoch */
	double secs;
	/** nanoseconds if any */
	int32_t nsec;
	/** offset in minutes from UTC */
	int32_t offset;
};

]]

local datetime_double_t = ffi.typeof('struct datetime_double')

local function datetime_new_raw(secs, nsec, offset)
    local dt_obj = ffi.new(datetime_t)
    dt_obj.secs = secs
    dt_obj.nsec = nsec
    dt_obj.offset = offset
    return dt_obj
end


local function datetime_new_raw_2(secs, nsec, offset)
    local dt_obj = ffi.new(datetime_double_t)
    dt_obj.secs = secs
    dt_obj.nsec = nsec
    dt_obj.offset = offset
    return dt_obj
end

local function datetime_index(self, key)
    if key == 'epoch' or key == 'unixtime' then
        return self.secs
    elseif key == 'secsf' then
        return builtin.datetime_secs(self)
    elseif key == 'ts' or key == 'timestamp' then
        return tonumber(self.secs) + self.nsec / 1e9
    elseif key == 'ns' or key == 'nanoseconds' then
        return self.secs * 1e9 + self.nsec
    elseif key == 'us' or key == 'microseconds' then
        return self.secs * 1e6 + self.nsec / 1e3
    elseif key == 'ms' or key == 'milliseconds' then
        return self.secs * 1e3 + self.nsec / 1e6
    elseif key == 's' or key == 'seconds' then
        return tonumber(self.secs) + self.nsec / 1e9
    elseif key == 'm' or key == 'min' or key == 'minutes' then
        return (tonumber(self.secs) + self.nsec / 1e9) / 60
    elseif key == 'hr' or key == 'hours' then
        return (tonumber(self.secs) + self.nsec / 1e9) / (60 * 60)
    elseif key == 'd' or key == 'days' then
        return (tonumber(self.secs) + self.nsec / 1e9) / (24 * 60 * 60)
    else
        error(('unknown attribute %s'):format(key), 2)
    end
end

local function datetime_newindex(self, key, value)
    if key == 'epoch' or key == 'unixtime' then
        self.secs = value
        self.nsec, self.offset = 0, 0
    else
        error(('assigning to unknown attribute %s'):format(key), 2)
    end
end

local datetime_mt = {
    __index = datetime_index,
    __newindex = datetime_newindex,
}

-- ffi.metatype(datetime_t, datetime_mt)


local _
local T

T = datetime_new_raw(60, 100000, 180)
print(ffi.typeof(T))

local start = clock.time()
for _ = 1, 1e6 do
    _ = T.secs
end
print('date.secs', clock.time() - start)

collectgarbage()
collectgarbage()
print(ffi.typeof(T))

start = clock.time()
for _ = 1, 1e6 do
    _ = T.secsf
end
print('date.secsf', clock.time() - start)
collectgarbage()
collectgarbage()

local N = datetime_new_raw_2(60, 100000, 180)
print(ffi.typeof(N))

start = clock.time()
for _ = 1, 1e6 do
    _ = N.secs
end
print('date_double.secs', clock.time() - start)

gistfile0.txt

diff --git a/extra/exports b/extra/exports
index 4100d500a..d34a54f62 100644
--- a/extra/exports
+++ b/extra/exports
@@ -152,6 +152,7 @@ datetime_asctime
 datetime_ctime
 datetime_now
 datetime_pack
+datetime_secs
 datetime_strftime
 datetime_to_string
 datetime_unpack
diff --git a/src/lib/core/datetime.c b/src/lib/core/datetime.c
index 7b65e28db..001f7e60f 100644
--- a/src/lib/core/datetime.c
+++ b/src/lib/core/datetime.c
@@ -75,6 +75,12 @@ datetime_now(struct datetime *now)
 	now->offset = tm.tm_gmtoff / 60;
 }
 
+double
+datetime_secs(const struct datetime *t)
+{
+	return (double)t->secs;
+}
+
 char *
 datetime_asctime(const struct datetime *date, char *buf)
 {
diff --git a/src/lua/datetime.lua b/src/lua/datetime.lua
index 5b1cbada9..c4d16028b 100644
--- a/src/lua/datetime.lua
+++ b/src/lua/datetime.lua
@@ -57,6 +57,8 @@ ffi.cdef [[
     void
     datetime_now(struct datetime * now);
 
+    double
+    datetime_secs(const struct datetime *t);
 ]]
 
 local builtin = ffi.C
@@ -737,6 +739,8 @@ end
 local function datetime_index(self, key)
     if key == 'epoch' or key == 'unixtime' then
         return self.secs
+    elseif key == 'secsf' then
+        return builtin.datetime_secs(self)
     elseif key == 'ts' or key == 'timestamp' then
         return tonumber(self.secs) + self.nsec / 1e9
     elseif key == 'ns' or key == 'nanoseconds' then

gistfile2.txt

✔ ~/datetime/tarantoolt/build [tsafin/gh-5941-datetime-v4 ↑·4|✚ 3…4⚑ 3] 
23:40 $ ./src/tarantool ../../bench-hash-dt.lua 
ctype<struct datetime>
date.secs       0.00035929679870605
ctype<struct datetime>
date.secsf      0.49544525146484
ctype<struct datetime_double>
date_double.secs        0.00042939186096191
✔ ~/datetime/tarantoolt/build [tsafin/gh-5941-datetime-v4 ↑·4|✚ 3…4⚑ 3] 
23:40 $ ./src/tarantool ../../bench-hash-dt.lua 
ctype<struct datetime>
date.secs       0.00034856796264648
ctype<struct datetime>
date.secsf      0.40926361083984
ctype<struct datetime_double>
date_double.secs        0.00043344497680664
✔ ~/datetime/tarantoolt/build [tsafin/gh-5941-datetime-v4 ↑·4|✚ 3…4⚑ 3] 
23:40 $ ./src/tarantool ../../bench-hash-dt.lua 
ctype<struct datetime>
date.secs       0.00034213066101074
ctype<struct datetime>
date.secsf      0.46818256378174
ctype<struct datetime_double>
date_double.secs        0.00037813186645508
✔ ~/datetime/tarantoolt/build [tsafin/gh-5941-datetime-v4 ↑·4|✚ 3…4⚑ 3] 
23:40 $ ./src/tarantool ../../bench-hash-dt.lua 
ctype<struct datetime>
date.secs       0.00051259994506836
ctype<struct datetime>
date.secsf      0.6695671081543
ctype<struct datetime_double>
date_double.secs        0.00048208236694336

jit-on-vs-off.md

jit.off()

✔ ~/datetime/tarantoolt/build [tsafin/msgpack-format L|✚ 1…6⚑ 3] 
14:47 $ ./src/tarantool ../../bench-hash-dt.lua 
ctype<struct datetime>
date.secs       0.25970935821533
ctype<struct datetime_double>
date_double.secs        0.15149474143982
✔ ~/datetime/tarantoolt/build [tsafin/msgpack-format L|✚ 1…6⚑ 3] 
14:48 $ ./src/tarantool ../../bench-hash-dt.lua 
ctype<struct datetime>
date.secs       0.33055567741394
ctype<struct datetime_double>
date_double.secs        0.18803310394287
✔ ~/datetime/tarantoolt/build [tsafin/msgpack-format L|✚ 1…6⚑ 3] 
14:48 $ ./src/tarantool ../../bench-hash-dt.lua 
ctype<struct datetime>
date.secs       0.29576468467712
ctype<struct datetime_double>
date_double.secs        0.15472149848938
✔ ~/datetime/tarantoolt/build [tsafin/msgpack-format L|✚ 1…6⚑ 3] 
14:48 $ ./src/tarantool ../../bench-hash-dt.lua 
ctype<struct datetime>
date.secs       0.2386200428009
ctype<struct datetime_double>
date_double.secs        0.1287829875946

jit.on()

✔ ~/datetime/tarantoolt/build [tsafin/msgpack-format L|✚ 1…6⚑ 3] 
14:46 $ ./src/tarantool ../../bench-hash-dt.lua 
ctype<struct datetime>
date.secs       0.0029795169830322
ctype<struct datetime_double>
date_double.secs        0.00043296813964844
✔ ~/datetime/tarantoolt/build [tsafin/msgpack-format L|✚ 1…6⚑ 3] 
14:47 $ ./src/tarantool ../../bench-hash-dt.lua 
ctype<struct datetime>
date.secs       0.00053858757019043
ctype<struct datetime_double>
date_double.secs        0.00038242340087891
✔ ~/datetime/tarantoolt/build [tsafin/msgpack-format L|✚ 1…6⚑ 3] 
14:47 $ ./src/tarantool ../../bench-hash-dt.lua 
ctype<struct datetime>
date.secs       0.00038433074951172
ctype<struct datetime_double>
date_double.secs        0.00033235549926758
✔ ~/datetime/tarantoolt/build [tsafin/msgpack-format L|✚ 1…6⚑ 3] 
14:47 $ ./src/tarantool ../../bench-hash-dt.lua 
ctype<struct datetime>
date.secs       0.0003509521484375
ctype<struct datetime_double>
date_double.secs        0.00031447410583496