zmaxheap.c

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/* Copyright (C) 2013-2016, The Regents of The University of Michigan.
All rights reserved.

This software was developed in the APRIL Robotics Lab under the
direction of Edwin Olson, ebolson@umich.edu. This software may be
available under alternative licensing terms; contact the address above.

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modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this
   list of conditions and the following disclaimer.
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   this list of conditions and the following disclaimer in the documentation
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ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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*/

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <assert.h>
#include <stdint.h>

#include "zmaxheap.h"

//                 0
//         1               2
//      3     4        5       6
//     7 8   9 10    11 12   13 14
//
// Children of node i:  2*i+1, 2*i+2
// Parent of node i: (i-1) / 2
//
// Heap property: a parent is greater than (or equal to) its children.

#define MIN_CAPACITY 16

struct zmaxheap
{
    size_t el_sz;

    int size;
    int alloc;

    float *values;
    char *data;

    void (*swap)(zmaxheap_t *heap, int a, int b);
};

static inline void swap_default(zmaxheap_t *heap, int a, int b)
{
    float t = heap->values[a];
    heap->values[a] = heap->values[b];
    heap->values[b] = t;

    char tmp[heap->el_sz];
    memcpy(tmp, &heap->data[a*heap->el_sz], heap->el_sz);
    memcpy(&heap->data[a*heap->el_sz], &heap->data[b*heap->el_sz], heap->el_sz);
    memcpy(&heap->data[b*heap->el_sz], tmp, heap->el_sz);
}

static inline void swap_pointer(zmaxheap_t *heap, int a, int b)
{
    float t = heap->values[a];
    heap->values[a] = heap->values[b];
    heap->values[b] = t;

    void **pp = (void**) heap->data;
    void *tmp = pp[a];
    pp[a] = pp[b];
    pp[b] = tmp;
}


zmaxheap_t *zmaxheap_create(size_t el_sz)
{
    zmaxheap_t *heap = calloc(1, sizeof(zmaxheap_t));
    heap->el_sz = el_sz;

    heap->swap = swap_default;

    if (el_sz == sizeof(void*))
        heap->swap = swap_pointer;

    return heap;
}

void zmaxheap_destroy(zmaxheap_t *heap)
{
    free(heap->values);
    free(heap->data);
    memset(heap, 0, sizeof(zmaxheap_t));
    free(heap);
}

int zmaxheap_size(zmaxheap_t *heap)
{
    return heap->size;
}

void zmaxheap_ensure_capacity(zmaxheap_t *heap, int capacity)
{
    if (heap->alloc >= capacity)
        return;

    int newcap = heap->alloc;

    while (newcap < capacity) {
        if (newcap < MIN_CAPACITY) {
            newcap = MIN_CAPACITY;
            continue;
        }

        newcap *= 2;
    }

    heap->values = realloc(heap->values, newcap * sizeof(float));
    heap->data = realloc(heap->data, newcap * heap->el_sz);
    heap->alloc = newcap;
}

void zmaxheap_add(zmaxheap_t *heap, void *p, float v)
{

    assert (isfinite(v) && "zmaxheap_add: Trying to add non-finite number to heap.  NaN's prohibited, could allow INF with testing");
    zmaxheap_ensure_capacity(heap, heap->size + 1);

    int idx = heap->size;

    heap->values[idx] = v;
    memcpy(&heap->data[idx*heap->el_sz], p, heap->el_sz);

    heap->size++;

    while (idx > 0) {

        int parent = (idx - 1) / 2;

        // we're done!
        if (heap->values[parent] >= v)
            break;

        // else, swap and recurse upwards.
        heap->swap(heap, idx, parent);
        idx = parent;
    }
}

void zmaxheap_vmap(zmaxheap_t *heap, void (*f)())
{
    assert(heap != NULL);
    assert(f != NULL);
    assert(heap->el_sz == sizeof(void*));

    for (int idx = 0; idx < heap->size; idx++) {
        void *p = NULL;
        memcpy(&p, &heap->data[idx*heap->el_sz], heap->el_sz);
        if (p == NULL) {
            printf("Warning: zmaxheap_vmap item %d is NULL\n", idx);
            fflush(stdout);
        }
        f(p);
    }
}

// Removes the item in the heap at the given index.  Returns 1 if the
// item existed. 0 Indicates an invalid idx (heap is smaller than
// idx). This is mostly intended to be used by zmaxheap_remove_max.
int zmaxheap_remove_index(zmaxheap_t *heap, int idx, void *p, float *v)
{
    if (idx >= heap->size)
        return 0;

    // copy out the requested element from the heap.
    if (v != NULL)
        *v = heap->values[idx];
    if (p != NULL)
        memcpy(p, &heap->data[idx*heap->el_sz], heap->el_sz);

    heap->size--;

    // If this element is already the last one, then there's nothing
    // for us to do.
    if (idx == heap->size)
        return 1;

    // copy last element to first element. (which probably upsets
    // the heap property).
    heap->values[idx] = heap->values[heap->size];
    memcpy(&heap->data[idx*heap->el_sz], &heap->data[heap->el_sz * heap->size], heap->el_sz);

    // now fix the heap. Note, as we descend, we're "pushing down"
    // the same node the entire time. Thus, while the index of the
    // parent might change, the parent_score doesn't.
    int parent = idx;
    float parent_score = heap->values[idx];

    // descend, fixing the heap.
    while (parent < heap->size) {

        int left = 2*parent + 1;
        int right = left + 1;

//            assert(parent_score == heap->values[parent]);

        float left_score = (left < heap->size) ? heap->values[left] : -INFINITY;
        float right_score = (right < heap->size) ? heap->values[right] : -INFINITY;

        // put the biggest of (parent, left, right) as the parent.

        // already okay?
        if (parent_score >= left_score && parent_score >= right_score)
            break;

        // if we got here, then one of the children is bigger than the parent.
        if (left_score >= right_score) {
            assert(left < heap->size);
            heap->swap(heap, parent, left);
            parent = left;
        } else {
            // right_score can't be less than left_score if right_score is -INFINITY.
            assert(right < heap->size);
            heap->swap(heap, parent, right);
            parent = right;
        }
    }

    return 1;
}

int zmaxheap_remove_max(zmaxheap_t *heap, void *p, float *v)
{
    return zmaxheap_remove_index(heap, 0, p, v);
}

void zmaxheap_iterator_init(zmaxheap_t *heap, zmaxheap_iterator_t *it)
{
    memset(it, 0, sizeof(zmaxheap_iterator_t));
    it->heap = heap;
    it->in = 0;
    it->out = 0;
}

int zmaxheap_iterator_next(zmaxheap_iterator_t *it, void *p, float *v)
{
    zmaxheap_t *heap = it->heap;

    if (it->in >= zmaxheap_size(heap))
        return 0;

    *v = heap->values[it->in];
    memcpy(p, &heap->data[it->in*heap->el_sz], heap->el_sz);

    if (it->in != it->out) {
        heap->values[it->out] = heap->values[it->in];
        memcpy(&heap->data[it->out*heap->el_sz], &heap->data[it->in*heap->el_sz], heap->el_sz);
    }

    it->in++;
    it->out++;
    return 1;
}

int zmaxheap_iterator_next_volatile(zmaxheap_iterator_t *it, void *p, float *v)
{
    zmaxheap_t *heap = it->heap;

    if (it->in >= zmaxheap_size(heap))
        return 0;

    *v = heap->values[it->in];
    *((void**) p) = &heap->data[it->in*heap->el_sz];

    if (it->in != it->out) {
        heap->values[it->out] = heap->values[it->in];
        memcpy(&heap->data[it->out*heap->el_sz], &heap->data[it->in*heap->el_sz], heap->el_sz);
    }

    it->in++;
    it->out++;
    return 1;
}

void zmaxheap_iterator_remove(zmaxheap_iterator_t *it)
{
    it->out--;
}

static void maxheapify(zmaxheap_t *heap, int parent)
{
    int left = 2*parent + 1;
    int right = 2*parent + 2;

    int betterchild = parent;

    if (left < heap->size && heap->values[left] > heap->values[betterchild])
        betterchild = left;
    if (right < heap->size && heap->values[right] > heap->values[betterchild])
        betterchild = right;

    if (betterchild != parent) {
        heap->swap(heap, parent, betterchild);
        return maxheapify(heap, betterchild);
    }
}

#if 0 //won't compile if defined but not used
// test the heap property
static void validate(zmaxheap_t *heap)
{
    for (int parent = 0; parent < heap->size; parent++) {
        int left = 2*parent + 1;
        int right = 2*parent + 2;

        if (left < heap->size) {
            assert(heap->values[parent] > heap->values[left]);
        }

        if (right < heap->size) {
            assert(heap->values[parent] > heap->values[right]);
        }
    }
}
#endif
void zmaxheap_iterator_finish(zmaxheap_iterator_t *it)
{
    // if nothing was removed, no work to do.
    if (it->in == it->out)
        return;

    zmaxheap_t *heap = it->heap;

    heap->size = it->out;

    // restore heap property
    for (int i = heap->size/2 - 1; i >= 0; i--)
        maxheapify(heap, i);
}

void zmaxheap_test()
{
    int cap = 10000;
    int sz = 0;
    int32_t *vals = calloc(sizeof(int32_t), cap);

    zmaxheap_t *heap = zmaxheap_create(sizeof(int32_t));

    int maxsz = 0;
    int zcnt = 0;

    for (int iter = 0; iter < 5000000; iter++) {
        assert(sz == heap->size);

        if ((random() & 1) == 0 && sz < cap) {
            // add a value
            int32_t v = (int32_t) (random() / 1000);
            float fv = v;
            assert(v == fv);

            vals[sz] = v;
            zmaxheap_add(heap, &v, fv);
            sz++;

//            printf("add %d %f\n", v, fv);
        } else {
            // remove a value
            int maxv = -1, maxi = -1;

            for (int i = 0; i < sz; i++) {
                if (vals[i] > maxv) {
                    maxv = vals[i];
                    maxi = i;
                }
            }


            int32_t outv;
            float outfv;
            int res = zmaxheap_remove_max(heap, &outv, &outfv);
            if (sz == 0) {
                assert(res == 0);
            } else {
//                printf("%d %d %d %f\n", sz, maxv, outv, outfv);
                assert(outv == outfv);
                assert(maxv == outv);

                // shuffle erase the maximum from our list.
                vals[maxi] = vals[sz - 1];
                sz--;
            }
        }

        if (sz > maxsz)
            maxsz = sz;

        if (maxsz > 0 && sz == 0)
            zcnt++;
    }

    printf("max size: %d, zcount %d\n", maxsz, zcnt);
    free (vals);
}