Abstract:
A multiplier configured to obtain higher frequencies of exactly rounded results by adding an adjustment constant to intermediate products generated during iterative multiplication operations is disclosed. One such iterative multiplication operation is the Newton-Raphson iteration, which may be utilized by the multiplier to perform reciprocal calculations and reciprocal square root calculations. For each iteration, the results converge toward an infinitely precise result. To improve the frequency of the exactly rounded result, the results of the iterative calculations may be studied for a large number of differing input operands to determine the best suited value for the adjustment constant. The multiplier may also be configured to perform scalar and packed vector multiplication using the same hardware.
Abstract:
An execution unit configured to perform a plurality of arithmetic operations using the same set of operands. These operands include corresponding input vector values in each of a plurality of input registers. The execution unit is coupled to receive these input vector values, as well as an instruction value indicative of one of the plurality of arithmetic operations. In one embodiment, the plurality of arithmetic operations includes a vectored add instruction, a vectored subtract instruction, a vectored reverse subtract instruction, and an accumulate instruction. The vectored instructions perform arithmetic operations concurrently using corresponding values from each of the plurality of input registers. The accumulate instruction, however, is executable to add together all input values within a single input register. The execution unit further includes a multiplexer unit configured to selectively route the input vector values to a plurality of adder units according to the opcode value. In an embodiment in which the execution unit is configured to perform subtraction operations as well as addition, the multiplexer unit is additionally configured to selectively route negated versions (either one's or two's complement format) to the plurality of adder units. Each of the plurality of adder units is configured to generate a sum based upon the values conveyed from the multiplexer unit. The accumulate instruction advantageously allows important operations such as the matrix multiply to be performed rapidly. Because the matrix multiply is an integral part of many applications (particularly graphics applications), the accumulate instruction may lead to increased overall system performance.
Abstract:
The present invention enables efficient matrix multiplication operations on parallel processing devices. One embodiment is a method for mapping CTAs to result matrix tiles for matrix multiplication operations. Another embodiment is a second method for mapping CTAs to result tiles. Yet other embodiments are methods for mapping the individual threads of a CTA to the elements of a tile for result tile computations, source tile copy operations, and source tile copy and transpose operations. The present invention advantageously enables result matrix elements to be computed on a tile-by-tile basis using multiple CTAs executing concurrently on different streaming multiprocessors, enables source tiles to be copied to local memory to reduce the number accesses from the global memory when computing a result tile, and enables coalesced read operations from the global memory as well as write operations to the local memory without bank conflicts.
Abstract:
In parallel processing devices, for streaming computations, processing of each data element of the stream may not be computationally intensive and thus processing may take relatively small amounts of time to compute as compared to memory accesses times required to read the stream and write the results. Therefore, memory throughput often limits the performance of the streaming computation. Generally stated, provided are methods for achieving improved, optimized, or ultimately, maximized memory throughput in such memory-throughput-limited streaming computations. Streaming computation performance is maximized by improving the aggregate memory throughput across the plurality of processing elements and threads. High aggregate memory throughput is achieved by balancing processing loads between threads and groups of threads and a hardware memory interface coupled to the parallel processing devices.
Abstract:
In parallel processing devices, for streaming computations, processing of each data element of the stream may not be computationally intensive and thus processing may take relatively small amounts of time to compute as compared to memory accesses times required to read the stream and write the results. Therefore, memory throughput often limits the performance of the streaming computation. Generally stated, provided are methods for achieving improved, optimized, or ultimately, maximized memory throughput in such memory-throughput-limited streaming computations. Streaming computation performance is maximized by improving the aggregate memory throughput across the plurality of processing elements and threads. High aggregate memory throughput is achieved by balancing processing loads between threads and groups of threads and a hardware memory interface coupled to the parallel processing devices.
Abstract:
An apparatus and method for superforwarding load operands in a microprocessor are provided. An execution unit in a microprocessor is configured to receive a load instruction and a subsequent instruction. If the load instruction corresponds to a simple load instruction, a destination operand of the load instruction can be superforwarded to a subsequent instruction if the subsequent instruction specifies a source operand that depends on the destination operand of the load instruction. The subsequent instruction is not required to wait until a load instruction executes or completes and can be scheduled and/or executed prior to or at the same time as the load instruction. Consequently, latencies associated with operand dependencies may be reduced.
Abstract:
A microprocessor configured to rapidly execute floating point store status word (FSTSW) type instructions that are immediately preceded by floating point compare (FCOM) type instructions is disclosed. FCOM-type instructions are modified to store their results to an architectural floating point status word and a temporary destination register. If an FSTSW-type instruction is detected immediately following an FCOM-type instruction, then the FSTSW-type instruction is transformed into a special fast floating point store status word (FSTSWEF) instruction. Unlike the FSTSW-type instruction, which is serializing and negatively impacts performance, the FSTSWEF instruction is not serializing and allows execution to continue without undue serialization. A computer system and method for rapidly executing FSTSW instructions immediately preceded by FCOM-type instructions are also disclosed.
Abstract:
An apparatus and method for executing floating-point store instructions in a microprocessor is provided. If store data of a floating-point store instruction corresponds to a tiny number and an underflow exception is masked, then a trap routine can be executed to generate corrected store data and complete the store operation. In response to detecting that store data corresponds to a tiny number and the underflow exception is masked, the store data, store address information, and opcode information can be stored prior to initiating the trap routine. The trap routine can be configured to access the store data, store address information, and opcode information. The trap routine can be configured to generate corrected store data and complete the store operation using the store data, store address information, and opcode information.
Abstract:
A multi-function look-up table for determining output values for predetermined ranges of a first mathematical function and a second mathematical function. In one embodiment, the multi-function look-up table is a bipartite look-up table including a first plurality of storage locations and a second plurality of storage locations. The first plurality of storage locations store base values for the first and second mathematical functions. Each base value is an output value (for either the first or second function) corresponding to an input region which includes the look-up table input value. The second plurality of storage locations, on the other hand, store difference values for both the first and second mathematical functions. These difference values are used for linear interpolation in conjunction with a corresponding base value in order to generate a look-up table output value. The multi-function look-up table further includes an address control unit coupled to receive a first input value and a signal which indicates whether an output value is to be generated for the first or second mathematical function. The address control unit then generates a first address value from these signals which is in turn conveyed to the first and second plurality of storage locations. In response to receiving the first address value, the first and second plurality of storage locations are configured to output a first base value and a first difference value, respectively. The first base value and first difference value are then conveyed to an output unit configured to generate a look-up table output value from the two values.
Abstract:
A multiplier capable of performing signed and unsigned scalar and vector multiplication is disclosed. The multiplier is configured to receive signed or unsigned multiplier and multiplicand operands in scalar or packed vector form. An effective sign for the multiplier and multiplicand operands may be calculated and used to create and select a number of partial products according to Booth's algorithm. Once the partial products have been created and selected, they may be summed and the results may be output. The results may be signed or unsigned, and may represent vector or scalar quantities. When a vector multiplication is performed, the multiplier may be configured to generate and select partial products so as to effectively isolate the multiplication process for each pair of vector components. The multiplier may also be configured to sum the products of the vector components to form the vector dot product. The final product may be output in segments so as to require fewer bus lines. The segments may be rounded by adding a rounding constant. Rounding and normalization may be performed in two paths, one assuming an overflow will occur, the other assuming no overflow will occur. The multiplier may also be configured to perform iterative calculations to evaluate constant powers of an operand. Intermediate products that are formed may be rounded and normalized in two paths and then compressed and stored for use in the next iteration. An adjustment constant may also be added to increase the frequency of exactly rounded results.