Digital Equipment Corporation

Hewlett-packard Development Company, L.p.

Alta Vista Company

Computer Computer Corporation

Charles Gregory Nelson

Andrei Z Broder

David L Detlefs

Mark Steven Manasse

Steven Charles Glassman

James Benjamin Saxe

Geoffrey G Zweig

Hui Chao

Michael Burrows

Edward Pearce Wobber

Xiaofan Lin

Andrew David Birrell

Susan S Owicki

Stefan Savage

Patrick G Sobalvarro

Methods, systems and machine-readable instructions for processing an electronic document are described. In one aspect, logical blocks that were extracted from the electronic document, including a text block comprising text lines each encompassed by a respective bounding rectangle, are received. Edges of ones of the bounding rectangles are extended to at least one boundary without changing layout relationships among the logical blocks in the electronic document. A text layout boundary is generated from extended and unextended edges of the bounding rectangles. A description of the text layout boundary is stored in a machine-readable medium.

Generating a text layout boundary from a text block in an electronic document

A tool and method for automatically producing near-optimal code sequences are particularly useful for generating near-optimal code sequences in inner loops, crucial subroutines, and device drivers. As a novel functional and architectural strategy, the invention contemplates applying technologies that would be normally in automatic theorem proving to the problem of automatic code generation. The aspect of the automatic theorem proving is realized by matching followed by planning with satisfiability search. Notably also, the present invention targets a goal-oriented, cycle budget limited code sequence in producing the near-optimal code sequence.

Code generation by matching and satisfiability search

The instructions in a computer program are converted into a form of weakest precondition so as to produce a verification condition that is to be evaluated by a theorem prover. In generating the weakest precondition, labels are introduced for values of variables at control join points. In two preferred embodiments, the computer program is converted into a set of guarded commands prior to the application of weakest precondition operators. In one embodiment, as part of the process of generating the verification condition, assignment commands that assign values to variables are removed from the program through use of a &ldquo;dynamic single assumption&rdquo; technique. In another embodiment, the weakest precondition is expressed in terms of strongest postconditions. In both embodiments, a simplified verification condition is produced in which duplications of sets of instructions following a choice operator is avoided.

Case-reduced verification condition generation system and method using weakest precondition operator expressed using strongest postcondition operators

A computer-implemented method determines the resemblance of data objects such as Web pages. Each data object is partitioned into a sequence of tokens. The tokens are grouped into overlapping sets of the tokens to form shingles. Each shingle is represented by a unique identification element encoded as a fingerprint. A minimum element from each of the images of the set of fingerprints associated with a document under each of a plurality of pseudo random permutations of the set of all fingerprints are selected to generate a sketch of each data object. The sketches characterize the resemblance of the data objects. The sketches can be further partitioned into a plurality of groups. Each group is fingerprinted to form a feature. Data objects that share more than a certain numbers of features are estimated to be nearly identical.

Method for clustering closely resembling data objects

A system and method for increasing the speed of operation of a theorem prover relating to program verification using adaptive pattern matching technique is disclosed. Source code in a specific programming language is converted to one or more formulae, each representing a specific reformulation of the source code that facilitates program verification. Each formula derived from the source code is converted into an E-graph which is a particular type of a directed acyclic graph having leaf nodes and interior nodes. Some of the nodes of an E-graph may be related to other nodes through equivalence relationships. Equivalence relationships between a group of nodes is stored in a data structure called an equivalence class. A collection of rules defining the grammar of the programming language is stored in an axiom database. Rules and conjectures can dynamically be added to the axiom database. Each rule or conjecture to be tested is converted into a pattern. The task of proving a rule or verifying some or all of the source code is transformed to the task of matching a pattern associated with the rule against the nodes of the E-graph. After each round of matching, the E-graph is modified by the addition of new equivalence relationships.

System and method for program verification and optimization

A method for facilitating the comparison of two computerized documents. The method includes loading a first document into a random access memory (RAM), loading a second document into the RAM, reducing the first document into a first sequence of tokens, reducing the second document into a second sequence of tokens, converting the first set of tokens to a first (multi)set of shingles, converting the second set of tokens to a second (multi)set of shingles, determining a first sketch of the first (multi)set of shingles, determining a second sketch of the second (multi)set of shingles, and comparing the first sketch and the second sketch. The sketches have a fixed size, independent of the size of the documents. The resemblance of two documents is provided using a sketch of each document. The sketches may be computed fairly fast and given two sketches the resemblance of the corresponding documents can be computed in linear time in the size of the sketches.

Method for determining the resemining the resemblance of documents

A computer implemented method detects concurrency errors in programs. Machine executable images of multiple program threads are instrumented to locate and replace instructions which affect concurrency states of the threads. Concurrency state information is recorded in a memory while the multiple threads are executing. The recorded concurrency state information is analyzed, and inconsistent dynamic concurrency state transitions are reported as concurrency errors.

Detecting concurrency errors in multi-threaded programs

Method for determining the resemblance of documents

A distributed computer system includes a multiplicity of concurrently active processes. Each object is owned by one process. Objects are accessible to processes other than the object's owner. Each process, when it receives a handle to an object owned by any other process, sends a first 'dirty' message to the object's owner indicating that the object is in use. When a process permanently ceases use of an object handle, it sends a second 'clean' message to the object's owner indicating that the object is no longer in use. Each object's owner receives the first and second messages concerning usage of that object, stores data for keeping track of which other processes have a handle to that object and sends acknowledgement messages in return. The receiver of an object handle does not use the handle until its first message is acknowledged. Periodically, the object's owner sends status request messages to other processes with outstanding handles to that object to determine if any of those processes have terminated and updates its stored object usage data accordingly. A garbage collection process collects objects for which the usage data indicates that no process has a handle. The first and second messages include sequence numbers, wherein the sequence numbers sent by any process change in value monotonically in accordance with when the message is sent. Object owners ignore any message whose sequence number indicates that it was sent earlier than another message for the same object that previously received from the same process.

Growing community of inventors

Palo Alto, CA, United States of America

Charles Gregory Nelson