From 599bbfd06e195a3eaed1069f2ed18fb3610198c4 Mon Sep 17 00:00:00 2001 From: Paweł Redman Date: Tue, 25 Sep 2018 23:55:45 +0200 Subject: Add a divide-less version of mastur. --- src/main.c | 4 +++- src/mastur2.c | 19 +++++++++++++++++++ 2 files changed, 22 insertions(+), 1 deletion(-) create mode 100644 src/mastur2.c (limited to 'src') diff --git a/src/main.c b/src/main.c index 6651ff3..4f7ba7f 100644 --- a/src/main.c +++ b/src/main.c @@ -22,6 +22,7 @@ int new32(int i, int x, int y); int new32v2(int i, int x, int y); int new32v3(int i, int x, int y); int mastur(int i, int x, int y); +int mastur2(int i, int x, int y); void bigtab_init(void); int bigtab(int i, int x, int y); @@ -42,7 +43,8 @@ static struct solfunc solfuncs[ ] = { {"new32", new32}, {"new32v2", new32v2}, {"new32v3", new32v3}, - {"mastur", mastur} + {"mastur", mastur}, + {"mastur2", mastur2} }; #define PASSES 5 diff --git a/src/mastur2.c b/src/mastur2.c new file mode 100644 index 0000000..1be6d1d --- /dev/null +++ b/src/mastur2.c @@ -0,0 +1,19 @@ +static const unsigned int divtab[244] = { + [1] = 0xffff + 1l, + [3] = 0x5555 + 1l, + [9] = 0x1c71 + 1l, + [27] = 0x097b + 1l, + [81] = 0x0329 + 1l, + [243] = 0x010d + 1l +}; + +#define FASTDIV(n, d) (((n) * divtab[d]) >> 16) +#define FASTMOD(n, d) ((n) - (d) * FASTDIV((n), (d))) + +static const int A[] = {0, 1, -1}; +static const int C[][3] = {{1, 1, -2}, {1, 1, -2}, {-2, 1, 1}}; + +int mastur2(const int i, const int x, const int y) +{ + return i + A[x] * C[x][FASTMOD(FASTDIV(i, y), 3)] * y; +} -- cgit