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[performance] Improve speed of our CRC-64 hasher (#624)
Modify the `Crc64` implementation to use splicing in order to process
data in a smaller number of iterations, at the expense of a bit more
memory for the extra tables. A quick test of calculating checksum for
a 1GB file shows a ~5.5x improvement:
Allocating 1043332542 bytes to hold file data
Reading file 'android-ndk-r21-linux-x86_64.zip' into memory
Calculating checksum using the old method... Hash: 197913BA13B9A1CC; Time: 00:00:04.0649818
Calculating checksum using the new method... Hash: 8203D033719B6B96; Time: 00:00:00.7251845
The calculated hash is different (although still stable and correct)
because the new code uses tables generated using a slightly different
set of parameters. Instead of using a single lookup table, the new
code takes the [slice-by-8 approach][0] which processes 8 bytes at a
time, using 8 lookup tables instead of one.
[Pycrc][1] was used to generate the `crc_update()` and `crc_reflect()`
methods, which were then ported to C# in [`gen-crc-tables.cs`][2], via:
pycrc.py --model crc-64-jones --std=C99 --algorithm bbf --generate {h,c} --reflect-out=true
Because the calculated hash now differs, we've changed the output
prefix from `crc64` to `c64r2`, to make the change slightly more
prominent and obvious.
Preliminary integration into xamarin-android shows build improvements
for a small Xamarin.Forms app, Debug configuration:
* First build:
Time Elapsed 00:00:36.74 (master)
Time Elapsed 00:00:34.43 (crc64)
* Incremental build (`.cs` file touched):
Time Elapsed 00:00:08.68 (master)
Time Elapsed 00:00:08.51 (crc64)
And for `<GenerateJavaStubs/>` task, which outputs 9.5MB of data:
* First build:
606 ms GenerateJavaStubs 1 calls (master)
570 ms GenerateJavaStubs 1 calls (crc64)
* Incremental build:
702 ms GenerateJavaStubs 1 calls (master)
617 ms GenerateJavaStubs 1 calls (crc64)
[0]: https://create.stephan-brumme.com/crc32/#slicing-by-8-overview
[1]: https://pycrc.org/index.html
[2]: https://gist.github.com/grendello/fdb968c795c310b389c611cb8c2fd7d5#file-gen-crc-tables-cs
const ulong POLY = 0xad93d23594c935a9;
static ulong[,] table = new ulong[8,256];
static ulong crc_reflect (ulong data, ulong data_len)
{
uint i;
ulong ret;
ret = data & 0x01;
for (i = 1; i < data_len; i++) {
data >>= 1;
ret = (ret << 1) | (data & 0x01);
}
return ret;
}
static ulong crc_update (ulong crc, byte[] data)
{
int idx = 0;
uint i;
bool bit;
byte c;
int data_len = data.Length;
while (data_len-- > 0) {
c = data[idx];
for (i = 0x01; (i & 0xff) != 0; i <<= 1) {
bit = (crc & 0x8000000000000000) != 0;
if ((c & i) != 0) {
bit = !bit;
}
crc <<= 1;
if (bit) {
crc ^= POLY;
}
}
crc &= 0xffffffffffffffff;
}
crc &= 0xffffffffffffffff;
return crc_reflect (crc, 64) ^ 0x0000000000000000;
}
static void GenerateTable ()
{
ulong crc;
byte[] b = { 0 };
for (int n = 0; n < 256; n++) {
b[0] = (byte)n;
table[0,n] = crc_update (0, b);
}
for (ulong n = 0; n < 256; n++) {
crc = table[0,n];
for (ulong k = 1; k < 8; k++) {
crc = table[0,crc & 0xff] ^ (crc >> 8);
table[k,n] = crc;
}
}
Console.WriteLine ("static readonly ulong[,] Table = {");
for (int i = 0; i < 8; i++) {
Console.WriteLine ("\t{");
for (int j = 0; j < 256; j++) {
if (j > 0) {
Console.Write (", ");
} else {
Console.Write ("\t\t");
}
if (j % 4 == 0) {
Console.WriteLine ();
Console.Write ("\t\t");
}
Console.Write ("0x");
Console.Write (table[i,j].ToString ("x16"));
}
Console.WriteLine ();
Console.WriteLine ("\t},");
}
Console.WriteLine ("};");
}
Copy file name to clipboardExpand all lines: tests/Java.Interop.Tools.JavaCallableWrappers-Tests/Java.Interop.Tools.JavaCallableWrappers/JavaCallableWrapperGeneratorTests.cs
+7-7Lines changed: 7 additions & 7 deletions
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Copy file name to clipboardExpand all lines: tests/Java.Interop.Tools.JavaCallableWrappers-Tests/Java.Interop.Tools.JavaCallableWrappers/JavaNativeTypeManagerTests.cs
Copy file name to clipboardExpand all lines: tests/Java.Interop.Tools.JavaCallableWrappers-Tests/Java.Interop.Tools.JavaCallableWrappers/TypeNameMapGeneratorTests.cs
+12-12Lines changed: 12 additions & 12 deletions
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