CSY/reowolf Changeset - 939a6de6ca76 · Centrum Wiskunde & Informatica (CWI)

Changeset - 939a6de6ca76

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Christopher Esterhuyse - 5 years ago 2020-02-14 15:24:53
christopher.esterhuyse@gmail.com

matrices seem very promising

1 file changed with 40 insertions and 26 deletions:

src/runtime/ecs.rs

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src/runtime/ecs.rs

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@@ @@ -75,55 +75,69 @@ impl BitSet { @@
+    }
+}
 /// Converts an iterator over contiguous u32 chunks into an iterator over usize
 /// e.g. input [0b111000, 0b11] gives output [3, 4, 5, 32, 33]
 /// observe that the bits per chunk are ordered from least to most significant bits, yielding smaller to larger usizes.
 /// works by draining the inner u32 chunk iterator one u32 at a time, then draining that chunk until its 0.
 struct BitChunkIter<I: Iterator<Item = u32>> {
     chunk_iter: I,
     next_bit_index: usize,
-    cached: Option<u32>, // None <=> iterator is done
     cached: u32,
+}
 impl<I: Iterator<Item = u32>> BitChunkIter<I> {
     fn new(mut chunk_iter: I) -> Self {
         let cached = chunk_iter.next();
         Self { chunk_iter, next_bit_index: 0, cached }
     fn new(chunk_iter: I) -> Self {
         // first chunk is always a dummy zero, as if chunk_iter yielded Some(0).
         // Consequences:
         // 1. our next_bit_index is always off by 32 (we correct for it in Self::next) (no additional overhead)
         // 2. we don't need to ever cache an Option. We can encounter them in Self::next.
         Self { chunk_iter, next_bit_index: 0, cached: 0 }
+    }
+}
 impl<I: Iterator<Item = u32>> Iterator for BitChunkIter<I> {
     type Item = usize;
     fn next(&mut self) -> Option<Self::Item> {
         loop {
             println!("LOOP");
             // get cached chunk. If none exists, iterator is done.
             let mut chunk = self.cached?;
             if chunk == 0 {
                 // self.next_bit_index jumps to next multiple of 32
         let mut chunk = self.cached;
         // loop until either:
         // 1. there are no more Items to return, or
         // 2. chunk encodes 1+ Items, one of which we will return.
         while chunk == 0 {
             // chunk is still empty! get the next one...
             chunk = self.chunk_iter.next()?;
             // ... and jump self.next_bit_index to the next multiple of 32.
             self.next_bit_index = (self.next_bit_index + 32) & !(32 - 1);
                 self.cached = self.chunk_iter.next();
                 continue;
+        }
             // this chunk encodes 1+ Items to yield
             // shift the contents of chunk until the least significant bit is 1
         // assert(chunk > 0);
         // Shift the contents of chunk until the least significant bit is 1.
         // ... being sure to increment next_bit_index accordingly.
         #[inline(always)]
-            fn shifty(chunk: &mut u32, shift_by: usize, next_bit_index: &mut usize) {
+        fn shift_and_inc(chunk: &mut u32, shift_by: usize, next_bit_index: &mut usize) {
             if *chunk & ((1 << shift_by) - 1) == 0 {
                 *next_bit_index += shift_by;
                 *chunk >>= shift_by;
+            }
-                println!("{:#032b}", *chunk);
+            // println!("{:#032b}", *chunk);
+        }
             shifty(&mut chunk, 16, &mut self.next_bit_index);
             shifty(&mut chunk, 08, &mut self.next_bit_index);
             shifty(&mut chunk, 04, &mut self.next_bit_index);
             shifty(&mut chunk, 02, &mut self.next_bit_index);
             shifty(&mut chunk, 01, &mut self.next_bit_index);
         shift_and_inc(&mut chunk, 16, &mut self.next_bit_index);
         shift_and_inc(&mut chunk, 08, &mut self.next_bit_index);
         shift_and_inc(&mut chunk, 04, &mut self.next_bit_index);
         shift_and_inc(&mut chunk, 02, &mut self.next_bit_index);
         shift_and_inc(&mut chunk, 01, &mut self.next_bit_index);
         // least significant bit of chunk is 1.
         // assert(chunk & 1 == 1)
         // prepare our state for the next time Self::next is called.
         // Overwrite self.cached such that its shifted state is retained,
         // and jump over the bit whose index we are about to return.
         self.next_bit_index += 1;
             self.cached = Some(chunk >> 1);
             if chunk > 0 {
                 return Some(self.next_bit_index - 1);
+            }
+        }
         self.cached = chunk >> 1;
         // returned index is 32 smaller than self.next_bit_index because we use an
         // off-by-32 encoding to avoid having to cache an Option<u32>.
         Some(self.next_bit_index - 1 - 32)
+    }
+}

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