Labyrinth generator

laby-7.c

// About 323MB/s on craptop
#include <unistd.h>
#include <stdlib.h>
unsigned int buf[8192];
unsigned int overflow[32];
int main() {
  int n;
  for(;;) {
    for(n = 0; n < sizeof(buf) / sizeof(buf[0]); ) {
      unsigned int r = rand();
      buf[n++] = 0x2f2f2f2f + 0x2d * (r & 0x01010101); r >>= 1; // 1
      buf[n++] = 0x2f2f2f2f + 0x2d * (r & 0x01010101); r >>= 1; // 2
      buf[n++] = 0x2f2f2f2f + 0x2d * (r & 0x01010101); r >>= 1; // 3
      buf[n++] = 0x2f2f2f2f + 0x2d * (r & 0x01010101); r >>= 1; // 4
      buf[n++] = 0x2f2f2f2f + 0x2d * (r & 0x01010101); r >>= 1; // 5
      buf[n++] = 0x2f2f2f2f + 0x2d * (r & 0x01010101); r >>= 1; // 6
      buf[n++] = 0x2f2f2f2f + 0x2d * (r & 0x01010101); r >>= 1; // 7
    }
    ssize_t s = write(1, buf, sizeof(buf));
  }
}

laby-ull-31-lut.c

// About 410MB/s on craptop
#include <unistd.h>
#include <stdlib.h>
unsigned long long lut[256];
unsigned long long buf[8192];
unsigned long long overflow[32];
int main() {
  long long n, m, a,b,c;
  char *p = (char *) lut;
  for (n = 0; n < 256; ++n)
    for (m = 0x80; m; m >>= 1)
      *p++ = (n & m) ? 0x2f : 0x5c;
  unsigned int r, q;
  for(;;) {
    for(n = 0; n < sizeof(buf) / sizeof(buf[0]); ) {
      r = rand();
      buf[n++] = lut[0xFF & r]; r >>= 8;
      buf[n++] = lut[0xFF & r]; r >>= 8;
      buf[n++] = lut[0xFF & r]; r >>= 8; // r has 7 random bits left
      q = rand();
      buf[n++] = lut[0xFF & q]; q >>= 8;
      buf[n++] = lut[0xFF & q]; q >>= 8;
      buf[n++] = lut[0xFF & q]; q >>= 8; // q has 7 random bits left
      r |= q << 7;
      buf[n++] = lut[0xFF & r]; r >>= 8; // r has 6 random bits left
      q = rand();
      buf[n++] = lut[0xFF & q]; q >>= 8;
      buf[n++] = lut[0xFF & q]; q >>= 8;
      buf[n++] = lut[0xFF & q]; q >>= 8; // q has 7 random bits left
      r |= q << 6;
      buf[n++] = lut[0xFF & r]; r >>= 8; // r has 5 random bits left
      q = rand();
      buf[n++] = lut[0xFF & q]; q >>= 8;
      buf[n++] = lut[0xFF & q]; q >>= 8;
      buf[n++] = lut[0xFF & q]; q >>= 8; // q has 7 random bits left
      r |= q << 5;
      buf[n++] = lut[0xFF & r]; r >>= 8; // r has 4 random bits left
      q = rand();
      buf[n++] = lut[0xFF & q]; q >>= 8;
      buf[n++] = lut[0xFF & q]; q >>= 8;
      buf[n++] = lut[0xFF & q]; q >>= 8; // q has 7 random bits left
      r |= q << 4;
      buf[n++] = lut[0xFF & r]; r >>= 8; // r has 3 random bits left
      q = rand();
      buf[n++] = lut[0xFF & q]; q >>= 8;
      buf[n++] = lut[0xFF & q]; q >>= 8;
      buf[n++] = lut[0xFF & q]; q >>= 8; // q has 7 random bits left
      r |= q << 3;
      buf[n++] = lut[0xFF & r]; r >>= 8; // r has 2 random bits left
      q = rand();
      buf[n++] = lut[0xFF & q]; q >>= 8;
      buf[n++] = lut[0xFF & q]; q >>= 8;
      buf[n++] = lut[0xFF & q]; q >>= 8; // q has 7 random bits left
      r |= q << 2;
      buf[n++] = lut[0xFF & r]; r >>= 8; // r has 1 random bits left
      q = rand();
      buf[n++] = lut[0xFF & q]; q >>= 8;
      buf[n++] = lut[0xFF & q]; q >>= 8;
      buf[n++] = lut[0xFF & q]; q >>= 8; // q has 7 random bits left
      r |= q << 1;
      buf[n++] = lut[0xFF & r]; r >>= 8; // r has 0 random bits left
    }
    ssize_t s = write(1, buf, sizeof(buf));
  }
}