mirror of
https://github.com/wassname/scikit-image.git
synced 2026-06-29 01:11:56 +08:00
Johannes Schönberger
136 lines
3.8 KiB
Cython
136 lines
3.8 KiB
Cython
"""
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Originally part of CellProfiler, code licensed under both GPL and BSD
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licenses.
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Website: http://www.cellprofiler.org
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Copyright (c) 2003-2009 Massachusetts Institute of Technology
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Copyright (c) 2009-2011 Broad Institute
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All rights reserved.
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Original author: Lee Kamentsky
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"""
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from libc.stdlib cimport free, malloc, realloc
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cdef struct Heap:
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Py_ssize_t items
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Py_ssize_t space
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Heapitem *data
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Heapitem **ptrs
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cdef inline Heap *heap_from_numpy2():
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cdef Py_ssize_t k
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cdef Heap *heap
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heap = <Heap *> malloc(sizeof (Heap))
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heap.items = 0
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heap.space = 1000
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heap.data = <Heapitem *> malloc(heap.space * sizeof(Heapitem))
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heap.ptrs = <Heapitem **> malloc(heap.space * sizeof(Heapitem *))
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for k in range(heap.space):
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heap.ptrs[k] = heap.data + k
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return heap
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cdef inline void heap_done(Heap *heap):
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free(heap.data)
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free(heap.ptrs)
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free(heap)
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cdef inline void swap(Py_ssize_t a, Py_ssize_t b, Heap *h):
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h.ptrs[a], h.ptrs[b] = h.ptrs[b], h.ptrs[a]
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######################################################
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# heappop - inlined
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#
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# pop an element off the heap, maintaining heap invariant
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#
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# Note: heap ordering is the same as python heapq, i.e., smallest first.
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######################################################
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cdef inline void heappop(Heap *heap, Heapitem *dest):
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cdef Py_ssize_t i, smallest, l, r # heap indices
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#
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# Start by copying the first element to the destination
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#
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dest[0] = heap.ptrs[0][0]
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heap.items -= 1
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# if the heap is now empty, we can return, no need to fix heap.
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if heap.items == 0:
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return
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#
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# Move the last element in the heap to the first.
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#
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swap(0, heap.items, heap)
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#
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# Restore the heap invariant.
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#
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i = 0
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smallest = i
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while True:
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# loop invariant here: smallest == i
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# find smallest of (i, l, r), and swap it to i's position if necessary
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l = i * 2 + 1 #__left(i)
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r = i * 2 + 2 #__right(i)
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if l < heap.items:
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if smaller(heap.ptrs[l], heap.ptrs[i]):
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smallest = l
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if r < heap.items and smaller(heap.ptrs[r], heap.ptrs[smallest]):
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smallest = r
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else:
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# this is unnecessary, but trims 0.04 out of 0.85 seconds...
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break
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# the element at i is smaller than either of its children, heap
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# invariant restored.
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if smallest == i:
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break
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# swap
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swap(i, smallest, heap)
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i = smallest
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##################################################
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# heappush - inlined
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#
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# push the element onto the heap, maintaining the heap invariant
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#
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# Note: heap ordering is the same as python heapq, i.e., smallest first.
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##################################################
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cdef inline void heappush(Heap *heap, Heapitem *new_elem):
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cdef Py_ssize_t child = heap.items
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cdef Py_ssize_t parent
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cdef Py_ssize_t k
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cdef Heapitem *new_data
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# grow if necessary
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if heap.items == heap.space:
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heap.space = heap.space * 2
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new_data = <Heapitem*>realloc(<void*>heap.data,
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<Py_ssize_t>(heap.space * sizeof(Heapitem)))
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heap.ptrs = <Heapitem**>realloc(<void*>heap.ptrs,
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<Py_ssize_t>(heap.space * sizeof(Heapitem *)))
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for k in range(heap.items):
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heap.ptrs[k] = new_data + (heap.ptrs[k] - heap.data)
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for k in range(heap.items, heap.space):
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heap.ptrs[k] = new_data + k
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heap.data = new_data
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# insert new data at child
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heap.ptrs[child][0] = new_elem[0]
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heap.items += 1
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# restore heap invariant, all parents <= children
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while child > 0:
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parent = (child + 1) / 2 - 1 # __parent(i)
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if smaller(heap.ptrs[child], heap.ptrs[parent]):
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swap(parent, child, heap)
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child = parent
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else:
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break
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