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+ GNU AFFERO GENERAL PUBLIC LICENSE
+ Version 3, 19 November 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>
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+ Preamble
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+ How to Apply These Terms to Your New Programs
+
+ If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+ To do so, attach the following notices to the program. It is safest
+to attach them to the start of each source file to most effectively
+state the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+ <one line to give the program's name and a brief idea of what it does.>
+ Copyright (C) <year> <name of author>
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU Affero General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU Affero General Public License for more details.
+
+ You should have received a copy of the GNU Affero General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+ If your software can interact with users remotely through a computer
+network, you should also make sure that it provides a way for users to
+get its source. For example, if your program is a web application, its
+interface could display a "Source" link that leads users to an archive
+of the code. There are many ways you could offer source, and different
+solutions will be better for different programs; see section 13 for the
+specific requirements.
+
+ You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU AGPL, see
+<http://www.gnu.org/licenses/>.
--- /dev/null
+// -*- mode: c; coding: utf-8 -*- */
+//
+// Copyright 2010, 2011, Matthias Andreas Benkard.
+//
+//-----------------------------------------------------------------------------
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program. If not, see <http://www.gnu.org/licenses/>.
+//-----------------------------------------------------------------------------
+//
+
+// An implementation of a bitmapped Patricia tree.
+
+//// Purpose ////
+//
+// The idea is to use a locally mutable, bitmapped Patricia tree as a
+// variable binding store (i.e. environment) in compiled code. In this
+// way, there is no need for excessive copying when an independent
+// environment must be set up (such as when initiating the processing of
+// a new node in the search space). Instead, significant amounts of
+// structure can be shared between child and parent environments.
+
+//// Motivation ////
+//
+// 1. Patricia trees are very amenable to structure sharing.
+//
+// 2. Furthermore, big-endian Patricia trees are especially efficient
+// when indices are allocated sequentially, as is the case for
+// variables in code emitted by our compiler.
+//
+// 3. Finally, bitmapping improves the performance of copying because
+// copying an array is much cheaper than copying an equivalent branch
+// in a tree. As we need to shallow-copy the tree at potentially
+// each choice point, copying needs to be fast.
+
+
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+#include "bitmapped_patricia_tree.h"
+
+typedef struct bpt_nonempty *bpt_nonempty_t;
+typedef struct bpt_node *bpt_node_t;
+typedef struct bpt_leaf *bpt_leaf_t;
+
+struct bpt {
+ enum bpt_tag tag;
+ int refcount;
+ bool mutable;
+ bpt_key_t prefix;
+};
+
+struct bpt_leaf {
+ struct bpt bpt; // poor man's inheritance
+ void *value;
+#ifdef BPT_ENABLE_DEALLOC_HOOKS
+ void (*dealloc_hook)(bpt_key_t, void *); // not actually used anywhere in client code
+#endif
+};
+
+struct bpt_node {
+ struct bpt bpt; // poor man's inheritance
+ unsigned int branching_chunk;
+ bpt_key_bitmask_t bitmask;
+ bpt_t *children;
+};
+
+
+void init_bpt_leaf(bpt_t a_leaf, bpt_key_t key, void *value) {
+ bpt_leaf_t leaf = (bpt_leaf_t)a_leaf;
+ leaf->bpt.tag = BPT_LEAF;
+ leaf->bpt.mutable = true;
+ leaf->bpt.prefix = key;
+ leaf->value = value;
+#ifdef BPT_ENABLE_DEALLOC_HOOKS
+ leaf->dealloc_hook = NULL;
+#endif
+ leaf->bpt.refcount = 1;
+}
+
+void init_bpt_node(bpt_node_t node, bpt_key_t prefix, unsigned int branching_chunk) {
+ node->bpt.tag = BPT_INNER_NODE;
+ node->bpt.mutable = true;
+ node->bpt.prefix = prefix;
+ node->branching_chunk = branching_chunk;
+ node->bitmask = 0;
+ node->children = NULL;
+ node->bpt.refcount = 1;
+}
+
+
+bpt_t bpt_make_leaf(bpt_key_t key, void *value) {
+ bpt_leaf_t leaf = malloc(sizeof *leaf);
+ init_bpt_leaf((bpt_t)leaf, key, value);
+ return (bpt_t)leaf;
+}
+
+bpt_node_t bpt_make_node(bpt_key_t prefix, unsigned int branching_chunk) {
+ bpt_node_t node = malloc(sizeof *node);
+ init_bpt_node(node, prefix, branching_chunk);
+ return node;
+}
+
+
+static inline unsigned int bpt_number_of_leading_zeros(bpt_key_t x);
+static inline unsigned int bpt_number_of_trailing_zeros(bpt_key_t x);
+static inline unsigned int bpt_popcount(bpt_key_bitmask_t key);
+static unsigned int bpt_compute_child_index(bpt_key_bitmask_t bitmask, unsigned int child_number);
+static inline uint_fast8_t bpt_offset_of_key(bpt_key_t key, unsigned int branching_chunk);
+static bpt_key_t bpt_prefix_of_key(bpt_key_t key, unsigned int branching_chunk);
+static inline unsigned int bpt_branching_chunk(bpt_t bpt);
+static unsigned int bpt_find_diverging_chunk(bpt_key_t key1, bpt_key_t key2);
+static void bpt_for_children(bpt_t bpt, void (*thunk)(bpt_t));
+
+
+static void bpt_for_children(bpt_t bpt, void (*thunk)(bpt_t)) {
+ if (bpt && bpt->tag == BPT_INNER_NODE) {
+ bpt_node_t b = (bpt_node_t)bpt;
+ bpt_t *iter = b->children;
+ bpt_t *children_end = b->children + bpt_popcount(b->bitmask);
+ while (iter < children_end) {
+ thunk(*iter);
+ iter++;
+ }
+ }
+}
+
+void *bpt_get(bpt_t bpt, bpt_key_t key) {
+ void **pointer = bpt_get_pointer(bpt, key);
+ if (pointer) {
+ return *pointer;
+ } else {
+ return NULL;
+ }
+}
+
+bpt_leaf_t bpt_get_leaf(bpt_t bpt, bpt_key_t key)
+{
+ if (!bpt) {
+ return NULL;
+ } else if (bpt->tag == BPT_LEAF) {
+ bpt_leaf_t b = (bpt_leaf_t)bpt;
+ if (bpt->prefix == key) {
+ return b;
+ } else {
+ return NULL;
+ }
+ } else {
+ bpt_node_t b = (bpt_node_t)bpt;
+ int child_number = bpt_offset_of_key(key, b->branching_chunk);
+ if ((1 << child_number) & b->bitmask) {
+ int child_index = bpt_compute_child_index(b->bitmask, child_number);
+ return bpt_get_leaf(b->children[child_index], key);
+ } else {
+ return NULL;
+ }
+ }
+}
+
+void **bpt_get_pointer(bpt_t bpt, bpt_key_t key)
+{
+ bpt_leaf_t leaf = bpt_get_leaf(bpt, key);
+ if (!leaf) {
+ return NULL;
+ } else {
+ return &leaf->value;
+ }
+}
+
+bool bpt_has_key(bpt_t bpt, bpt_key_t key) {
+ return (bpt_get_leaf(bpt, key) != NULL);
+}
+
+bpt_t bpt_assoc(bpt_t bpt, bpt_key_t key, void *value) {
+ if (!bpt) {
+ return (bpt_t)bpt_make_leaf(key, value);
+ } else {
+ bpt_key_t prefix = bpt->prefix;
+ if (bpt_prefix_of_key(key, bpt_branching_chunk(bpt)) != prefix) {
+ unsigned int diverging_chunk = bpt_find_diverging_chunk(key, prefix);
+ bpt_key_t my_number_in_parent = bpt_offset_of_key(prefix, diverging_chunk);
+ bpt_key_t their_number_in_parent = bpt_offset_of_key(key, diverging_chunk);
+ bpt_node_t new_node = bpt_make_node(bpt_prefix_of_key(prefix, diverging_chunk), diverging_chunk);
+ new_node->bitmask = (1 << my_number_in_parent) | (1 << their_number_in_parent);
+ new_node->children = malloc(sizeof (*new_node->children) * 2);
+ if (my_number_in_parent < their_number_in_parent) {
+ new_node->children[0] = bpt;
+ new_node->children[1] = bpt_make_leaf(key, value);
+ } else {
+ new_node->children[0] = bpt_make_leaf(key, value);
+ new_node->children[1] = bpt;
+ }
+ bpt_retain(bpt);
+ return (bpt_t)new_node;
+ } else {
+ if (bpt->tag == BPT_LEAF) {
+ bpt_leaf_t b = (bpt_leaf_t)bpt;
+ if (bpt->mutable) {
+ b->value = value;
+ bpt_retain(bpt);
+ return bpt;
+ } else {
+ return (bpt_t)bpt_make_leaf(key, value);
+ }
+ } else {
+ bpt_node_t b = (bpt_node_t)bpt;
+ uint_fast8_t child_number = bpt_offset_of_key(key, b->branching_chunk);
+ unsigned int child_index = bpt_compute_child_index(b->bitmask, child_number);
+ if ((1 << child_number) & b->bitmask) {
+ // We already have a child to pass the value to. Do that.
+ bpt_t child = b->children[child_index];
+ bpt_t new_child = bpt_assoc(child, key, value);
+ if (new_child == child) {
+ bpt_release(child);
+ bpt_retain(bpt);
+ return bpt;
+ } else {
+ if (bpt->mutable) {
+ bpt_release(child);
+ b->children[child_index] = new_child;
+ bpt_retain(bpt);
+ return bpt;
+ } else {
+ bpt_node_t new_node = malloc(sizeof *new_node);
+ *new_node = *b;
+ new_node->bpt.refcount = 1;
+ new_node->bpt.mutable = true;
+ unsigned int number_of_children = bpt_popcount(b->bitmask);
+ size_t size_of_child_array = sizeof (*new_node->children) * number_of_children;
+ new_node->children = malloc(size_of_child_array);
+ memcpy(new_node->children, b->children, size_of_child_array);
+ new_node->children[child_index] = new_child;
+ // Retain the children copied into the new node.
+ bpt_for_children((bpt_t)new_node, bpt_retain);
+ bpt_release(new_child);
+ return (bpt_t)new_node;
+ }
+ }
+ } else {
+ // Create a new child.
+ unsigned int number_of_children = bpt_popcount(b->bitmask);
+ size_t new_size_of_child_array = sizeof (*b->children) * (number_of_children + 1);
+ if (bpt->mutable) {
+ b->children = realloc(b->children, new_size_of_child_array);
+ memmove(b->children + child_index + 1, b->children + child_index, sizeof (*b->children) * (number_of_children - child_index));
+ b->children[child_index] = bpt_make_leaf(key, value);
+ b->bitmask |= 1 << child_number;
+ bpt_retain(bpt);
+ return bpt;
+ } else {
+ bpt_t *new_children = malloc(new_size_of_child_array);
+ memcpy(new_children, b->children, sizeof (*b->children) * child_index);
+ memcpy(new_children + child_index + 1,
+ b->children + child_index,
+ sizeof (*b->children) * (number_of_children - child_index));
+ new_children[child_index] = bpt_make_leaf(key, value);
+ bpt_node_t new_node = bpt_make_node(b->bpt.prefix, b->branching_chunk);
+ new_node->children = new_children;
+ new_node->bitmask = b->bitmask | (1 << child_number);
+ // Retain the children copied into the new node.
+ bpt_for_children(bpt, bpt_retain);
+ return (bpt_t)new_node;
+ }
+ }
+ }
+ }
+ }
+}
+
+
+bpt_t bpt_dissoc(bpt_t bpt, bpt_key_t key) {
+ if (!bpt || (bpt_prefix_of_key(key, bpt_branching_chunk(bpt)) != bpt->prefix)) {
+ bpt_retain(bpt);
+ return bpt;
+ } else if (bpt->tag == BPT_LEAF) {
+ // Key matches.
+ return NULL;
+ } else {
+ // Prefix matches.
+ bpt_node_t b = (bpt_node_t)bpt;
+ uint_fast8_t child_number = bpt_offset_of_key(key, b->branching_chunk);
+ if ((1 << child_number) & b->bitmask) {
+ unsigned int child_index = bpt_compute_child_index(b->bitmask, child_number);
+ bpt_t child = b->children[child_index];
+ bpt_t new_child = bpt_dissoc(child, key);
+ if (new_child == child) {
+ bpt_release(child);
+ bpt_retain(bpt);
+ return bpt;
+ } else {
+ unsigned int number_of_children = bpt_popcount(b->bitmask);
+ if (!new_child && number_of_children == 2) {
+ // When there is only a single child left, we replace ourselves
+ // with that child.
+ bpt_t remaining_child = b->children[1-child_index];
+ bpt_retain(remaining_child);
+ return remaining_child;
+ } else if (bpt->mutable) {
+ bpt_release(child);
+ if (!new_child) {
+ // We don't reallocate the array because it wouldn't really
+ // gain us anything (except maybe non-confusion of a
+ // conservative GC).
+ memmove(b->children + child_index, b->children + child_index + 1, sizeof(*b->children) * (number_of_children - child_index - 1));
+ b->bitmask &= ~(1 << child_number);
+ bpt_retain(bpt);
+ return bpt;
+ } else {
+ b->children[child_index] = new_child;
+ bpt_retain(bpt);
+ return bpt;
+ }
+ } else {
+ // If all else fails, allocate a new node.
+ bpt_t *new_children;
+ bpt_key_bitmask_t bitmask;
+ if (!new_child) {
+ new_children = malloc((sizeof *new_children) * (number_of_children - 1));
+ memcpy(new_children, b->children, sizeof (*b->children) * child_index);
+ memcpy(new_children + child_index,
+ b->children + child_index + 1,
+ sizeof (*b->children) * (number_of_children - child_index - 1));
+ bitmask = b->bitmask & ~(1 << child_number);
+ } else {
+ new_children = malloc((sizeof *new_children) * number_of_children);
+ memcpy(new_children, b->children, sizeof (*b->children) * number_of_children);
+ new_children[child_index] = new_child;
+ bitmask = b->bitmask;
+ }
+ bpt_node_t new_node = bpt_make_node(b->bpt.prefix, b->branching_chunk);
+ new_node->children = new_children;
+ new_node->bitmask = bitmask;
+ // Retain the children copied into the new node.
+ bpt_for_children((bpt_t)new_node, bpt_retain);
+ bpt_release(new_child);
+ return (bpt_t)new_node;
+ }
+ }
+ } else {
+ bpt_retain(bpt);
+ return bpt;
+ }
+ }
+}
+
+
+void bpt_seal(bpt_t bpt) {
+ if (bpt) {
+ if (bpt->mutable) {
+ bpt->mutable = false;
+ if (bpt->tag == BPT_INNER_NODE) {
+ bpt_for_children(bpt, bpt_seal);
+ }
+ }
+ }
+}
+
+
+/////////////// Helper functions ///////////////
+static unsigned int bpt_compute_child_index(bpt_key_bitmask_t bitmask, unsigned int child_number) {
+ // Compute the sparse array index given a flat array index.
+ return bpt_popcount(bitmask & ((1 << child_number) - 1));
+}
+
+static inline uint_fast8_t bpt_offset_of_key(bpt_key_t key, unsigned int chunk_number) {
+ // Little-enidan:
+ //return (key >> (chunk_number * CHUNK_LENGTH)) & OFFSET_MASK;
+ // Big-endian:
+ int shift = 0;
+ if (chunk_number <= MAX_CHUNKS - 2) {
+ shift += LAST_CHUNK_LENGTH;
+ }
+ if (chunk_number <= MAX_CHUNKS - 3) {
+ shift += ((MAX_CHUNKS - 2 - chunk_number) * CHUNK_LENGTH);
+ }
+ return (key >> shift) & (chunk_number == MAX_CHUNKS - 1 ? ((1 << LAST_CHUNK_LENGTH) - 1) : OFFSET_MASK);
+}
+
+static bpt_key_t bpt_prefix_of_key(bpt_key_t key, unsigned int chunk_number) {
+ if (chunk_number == MAX_CHUNKS) {
+ return key;
+ } else {
+ // Little-endian:
+ //return key & ((1 << (chunk_number * CHUNK_LENGTH)) - 1)
+ // Big-endian:
+ return key & (((1 << (chunk_number * CHUNK_LENGTH)) - 1) << (KEY_LENGTH - (chunk_number * CHUNK_LENGTH)));
+ }
+}
+
+static inline unsigned int bpt_branching_chunk(bpt_t bpt) {
+ assert(bpt);
+ if (bpt->tag == BPT_LEAF) {
+ return MAX_CHUNKS;
+ } else {
+ return ((bpt_node_t)bpt)->branching_chunk;
+ }
+}
+
+static inline unsigned int bpt_popcount(bpt_key_bitmask_t x) {
+ return __builtin_popcountll(x);
+}
+
+static inline unsigned int bpt_number_of_leading_zeros(bpt_key_t x) {
+ return __builtin_clzll(x);
+}
+
+static inline unsigned int bpt_number_of_trailing_zeros(bpt_key_t x) {
+ return __builtin_ctzll(x);
+}
+
+static unsigned int bpt_find_diverging_chunk(bpt_key_t a, bpt_key_t b) {
+ // Little-endian:
+ //return bpt_number_of_trailing_zeros(a ^ b) / CHUNK_LENGTH;
+ // Big-endian:
+ return bpt_number_of_leading_zeros(a ^ b) / CHUNK_LENGTH;
+}
+
+void bpt_retain(bpt_t bpt) {
+ if (bpt) {
+ __sync_fetch_and_add(&bpt->refcount, 1);
+ }
+}
+
+void bpt_release(bpt_t bpt) {
+ if (bpt) {
+ if (__sync_sub_and_fetch(&bpt->refcount, 1) == 0) {
+ bpt_dealloc(bpt);
+ }
+ }
+}
+
+void bpt_dealloc(bpt_t bpt) {
+ if (bpt) {
+ if (bpt->tag == BPT_LEAF) {
+ bpt_leaf_t b = (bpt_leaf_t)bpt;
+#ifdef BPT_ENABLE_DEALLOC_HOOKS
+ if (b->dealloc_hook) {
+ b->dealloc_hook(b->bpt.prefix, b->value);
+ }
+#endif
+ free(b);
+ } else {
+ bpt_node_t b = (bpt_node_t)bpt;
+ bpt_for_children(bpt, bpt_release);
+ free(b->children);
+ free(b);
+ }
+ }
+}
+
+#ifdef BPT_ENABLE_DEALLOC_HOOKS
+void bpt_leaf_set_dealloc_hook(bpt_leaf_t bpt, void (*hook)(bpt_key_t, void*)) {
+ if (bpt) {
+ bpt->dealloc_hook = hook;
+ }
+}
+
+void bpt_set_dealloc_hook(bpt_t bpt, bpt_key_t key, void (*hook)(bpt_key_t, void*)) {
+ bpt_leaf_set_dealloc_hook(bpt_get_leaf(bpt, key), hook);
+}
+#endif
projects / lazyeval.git / commitdiff