Exponential mapping and OpenMP
Robert Munafo pointed me at a cunning technique for transforming coordinates for optimizing zoom animation computations - it involves vastly less book-keeping than the ideas I've experimented with before and so makes it easier to do other clever things, like parallelizing with OpenMP:
...
do {
progress = 0;
#pragma omp parallel for private(p) reduction(||:progress) schedule(static, 1)
for (int x = 0; x < W; ++x) {
p = iteratePoint(y * W + x, count);
progress = progress || p;
}
} while (progress);
...which leads to some impressive scaling benchmarks:
| mode | time |
|---|---|
| plain (1 thread) | 10m02s |
| OpenMP (1 thread) | 10m27s |
| OpenMP (2 threads) | 5m22s |
Adding -fopenmp to the gcc flags is the only other thing needed to make it use another core and finish twice as quick, with attractive tall and thin results.
