Abstract: A method for synchronizing clocks in a distributed computing system in the presence of faults. The condition to be renewed guarantees that all clocks of correct processors never deviate by more than some maximum amount. This condition is achieved by periodically resynchronizing the clocks so that the correct clocks do not deviate by more than some minimum deviation. In the process of resynchronization, a correct clock is never adjusted by more than a maximum amount during a period and it is never set back.The method requires that there is a previously agreed upon ordered list of all participants. At a specified time in the period, the first processor on the list attempts to synchronize all to its clock. The result of this is either a synchronization of all correct processors and their clocks to be within the desired tolerance or an agreement among all other correct processors that the first node on the list has failed. If the first fails, then the second tries and so on.

Abstract: If object identity is written into pixel locations of the refresh buffer portion of a raster-driven display as objects are drawn or amended, and if such object identity is used to index color maps and tree-linked lists of multiple object displays, then editing functions, such as correlation and echoing, color mixing, and selective erasure, at the display level can be invoked and executed with a minimum of reprocessing of the display list at the host level.

Abstract: Method for managing a buffer pool shared by sequential and random processes. A data base manager includes a buffer manager which: (1) maintains a normal least recently used (LRU) buffer chain and a sequential LRU buffer chain, the sequential LRU buffer chain being replicated on the normal LRU buffer chain; (2) places buffers released from a sequential process in both LRU buffer chains and buffers released from a random process only in the normal LRU buffer chain; and (3) responsive to a request for a buffer for a sequential process, steals the head buffer from the sequential LRU buffer chain, otherwise steals the head buffer from the normal LRU buffer chain. The buffer manager further conditionally asynchronously prefetches data set pages from the external storage device in response to a request for a data set page which is an integral multiple of a process defined prefetch quantity.

Abstract: The invention provides a computing apparatus and method for maintaining a journal log. The computing apparatus includes volatile storage for storing a log buffer and a non-volatile storage for storing a journal log. Non-volatile storage means are provided for storing in a write-ahead data set a plurality of short data blocks. The log buffer contents are written to the write-ahead data set responsive to a process epoch occurring before the log buffer is filled. The log buffer contents are written to the journal log upon the log buffer being filled. The redoing or undoing of data base changes is made with reference to the write ahead data set only in the case of a system failure resulting in loss of log buffer data not yet written to the journal log; otherwise data base changes are redone or undone with reference to the log buffer or journal log.

Abstract: Preliminary classification of a text character by examining a few of its PELs rather than requiring repeated comparisons of the entire pattern with a large set of prototypes is achieved by following a path through a decision tree in a root-to-leaf node direction. Each tree node specifies the location of a PEL in the character and the input pattern PEL value in turn determines the next branch to follow in the tree. The root node identifies the first PEL to be inspected while the final leaf indicates the class selected. The library pattern and inputs are compared. Upon match, an index number is generated and the next pattern processed. Upon a mismatch, the pattern will be registered as a new prototype in the library, the tree extended to include the new class, and the next pattern will be processed.

Abstract: A method for assuring atomicity of user requested multi-row update operations to tables such as in a relational database, guarantees that for any update operation that succeeds all stated effects will have occurred and that for any update operation that fails the system state as perceived by the user remains unchanged. This is accomplished by establishing, in response to a multi-row update operation request, an execution module of a program containing sets of machine language code instructions implementing the update operation request with a savepoint request at the beginning of the execution module of the program. For each set of machine language code instructions in or called by the execution module which modified the user perceived system state, information is logged to a soft log.

Abstract: Two controller units controlling a single input/output device such as a cathode ray tube (CRT) are synchronized by a command signal. Upon appearance of the command signal, the slave controller unit, which may have been running unsynchronized with the master controller, is stopped at the time for vertical retrace and remains stopped until vertical retrace time for the master controller. At this point, the slave controller is restarted in synchronism with the master controller and remains synchronized so long as both master and slave receive the same clock and the same screen refresh parameters.

Abstract: A two-stage single pass adaptive modeling method and means for a finite alphabet first order MARKOV symbol source where the model is used to control an encoder on a per symbol basis thereby enabling efficient compression within a fixed preselected implementation complexity.

Abstract: A length oriented arithmetic decoder constrained to ONE-TO-ONE map in the data string to run length limited string direction and ONTO map in the run length limited to data string direction through an arithmetic encoder preserves the fixed rate of the RLL string and ensures representability. A finite state machine responsive to the arithmetic decoder output provides the trial augends and shift amounts necessary for the magnitude comparison decoding of the data string treated as if it were arithmetically compressed. A finite state machine is also used with the arithmetic encoder for providing trial augends and shift amounts but is responsive to successive RLL symbols as if it were ordinary source strings. The encoder combines the augends with a predetermined retained portion of the generated data string.

Abstract: In a column layout operation in an interactive word processing system, the unoccupied character escapement along a column example line is automatically evenly distributed by the insertion of an appropriate number of space characters responsive to the stroking of a predetermined function key.

Abstract: A page modification method in a printer subsystem of the partial page buffer composing type. A printer subsystem receives a packet containing a page of characters, coded overlays/elisions, and combining data from an external source. The packet is translated into a linked list of character placement representations for each of the doubly indexed coded characters within the page. Elisions from the page are made by inhibiting the formation of a linked list segment for each character sequence within elision markers set out in the page. In contrast, coded character overlays are appended to the list as addenda. The list governs the placement of characters into a partial page buffer, whose contents are system accessible in row major order.

Abstract: A method and apparatus for recursively generating an arithmetically compressed binary number stream responsive to the binary string from conditional sources. Throughput is increased by reducing the number of operations required to encode each binary symbol so that only a single shift of k bits is required upon receipt of each least-probable symbol or an "add time", followed by a decision and a one-bit shift in response to each most-probable symbol encoding. The concurrent augmentation of the compressed stream and an internal variable involves only the function of a probability interval estimate of the most-probable symbol, and not upon the past encoding state of either variable (2.sup.-k, 49, 63, C, T). Each binary symbol may be recovered by subtracting 2.sup.-k from the q-most-significant bits of the compressed stream and testing the leading bit of the difference.

Abstract: Carry-over control in strings resulting from the high to low order combining of two binary number strings is obtained through the insertion of a control character within the resultant string after detecting a run of consecutive 1's. Upon subsequent accessing and decomposition of the resultant string, the control character causes string decomposition to operate for a number of cycles in a carry correction mode. If the control character indicates that a carry has rippled through the n lesser significant positions of the resultant string, then upon decomposition, those "n" consecutive 1's are changed to 0's, and a 1 is added to the least significant position in the string preceding the control character. If the control character indicates no carry occurrence, then it is merely deleted from the string. The control of carries in this manner permits the generation of arithmetic string compression code sequences in an instantaneous FIFO pattern with only a modest reduction of compression efficiency.

Abstract: Short traces of consecutive CPU references to storage are accumulated and processed to ascertain hit ratio as a function of cache size. From this determination, an allocation of cache can be made. Because this determination requires minimal processing time, LRU-referenceable memory space among concurrently executing sequential processes is used dynamically by a CPU cache manager.

Abstract: A method for the automatic center tab insertion within a column example line comprising the steps of an operator cursor move to a column margin to define an end position; and responsive to a function key stroke, the machine steps of concurrently moving the cursor to the other column margin and counting the text characters of the example; calculating the distance to the column center position; concurrently moving the cursor to the calculated center position, and inserting a centered tab stop control character therein.

Abstract: In a wire matrix printer control system, some characters from a finite alphabet are locally stored as compressed dot matrix objects reflectively symmetric about at least one axis. Upon being referenced and ascertained as a compressed object, the bits are applied to the printhead in column major order up to the axis of symmetry and then applied in reverse column major order. For uncompressed objects, the bits are applied only in column major order.

Abstract: The automatic tab insertion in those null-entry positions in a tab-stopped positioned multicolumn table having row lines which include text right adjacent the null entries so as to inhibit right-to-left, text-to-null-entry migration in the same row.

Abstract: Weak synchronization and scheduling of each processor among concurrent asynchronous processors is governed by either task execution invoked by an external response indicating its low bid among the well-ordered set of most recently bid signals, task deferred until such indication is received from subsequent bid evaluations, or task aborted as by transfer to another task upon indication that an instantaneous bid was not the minimum.

Abstract: Flow graph related program segments having cyclic paths therethrough are efficiently processed on a SIMD machine by priority ordering the segments, selectively inserting ELSE/JOIN instructions as steps prior to enforcing the ordering when the network of program segments is executed on a SIMD machine.

Abstract: A CPU implementable method for minimizing thrashing among concurrent processes demand page accessing a data base through an LRU page organized buffer pool. There is ascertained the set of pages over which there is looping access behavior for the prospectively executing concurrent processes. This parameter, as determined for each task, is passed to the storage accessing component which partitions the buffer into LRU stacks and dynamically adjusts the stack to this predicted parameter size.