|Publication number||US7093102 B1|
|Application number||US 09/538,012|
|Publication date||15 Aug 2006|
|Filing date||29 Mar 2000|
|Priority date||29 Mar 2000|
|Publication number||09538012, 538012, US 7093102 B1, US 7093102B1, US-B1-7093102, US7093102 B1, US7093102B1|
|Original Assignee||Intel Corporation|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (7), Non-Patent Citations (2), Referenced by (5), Classifications (14), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
1. Field of the Invention
This invention relates generally to the field of processor operations. More particularly, the invention relates to an apparatus and method for performing vector gather and scatter operations using a computer processor.
2. Description of the Related Art
In order to perform vector computations on a computer, matrices such as that illustrated in
One problem which exists, however, is that matrices can take up a substantial amount of memory, particularly when used to store certain types of data (e.g., scientific data pertaining to physical phenomenon). In addition, matrices may be sparsely populated with data elements. For example, only 4 data elements out of the 24 illustrated in
To conserve memory when working such large, sparsely populated matrices, “gather” and “scatter” operations were developed. For example, the CRAY-1 computer system performed gather operations to collect the elements of a matrix from memory and store them in a highly compressed format (e.g., sorted contiguously in an ordered array). Conversely, when necessary to perform various matrix operations (e.g., matrix multiplication) the CRAY-1 performed scatter operations to reproduce the previously-gathered matrix in memory.
One problem which exists, however, is that these systems require complex dedicated hardware to perform the gather and scatter operations. For example, the CRAY-1 employed a vector processor which performed gather and scatter operations using dedicated registers to hold index vectors and dedicated address calculation hardware.
Accordingly, what is needed is a more efficient apparatus and method for storing and working with matrices in a computing environment. What is also needed is a system and method for performing gather and scatter operations on a general purpose processor.
A system and method are described for performing gather and scatter operations on a general purpose computer. For example, a method for performing a gather operation is described which includes the operations of: computing addresses for a plurality of data elements of a matrix stored in memory, wherein each data element is identified by one of an equal plurality of indices and a base address; and wherein computing addresses comprises executing an equal plurality of EXTRACT instructions to transfer a plurality of the indices from a first storage location where the indices are stored substantially contiguously, to an equal plurality of separate storage locations, wherein each index is assigned its own separate storage location; and adding the base address to each index, wherein each addition of the base address to each index is independent of one another; retrieving each of the plurality of data elements from memory based on the computed addresses; and executing an equal plurality of DEPOSIT instructions, each DEPOSIT instruction depositing one or more of the data elements contiguously with other data elements in a general purpose register.
A better understanding of the present invention can be obtained from the following detailed description in conjunction with the following drawings, in which:
In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some of these specific details. In other instances, well-known structures and devices are shown in block diagram form to avoid obscuring the underlying principles of the present invention.
Embodiments of the present invention include various steps, which will be described below. The steps may be embodied in machine-executable code. The instructions can be used to cause a general-purpose or special-purpose processor to perform certain steps. Alternatively, these steps may be performed by specific hardware components that contain hardwired logic for performing the steps, or by any combination of programmed computer components and custom hardware components.
The processor 210 includes an execution unit 230, a register file 250, a cache memory 260, a decoder 265, and an internal bus 270. The cache memory 260, storing frequently and/or recently used information for the processor 210, is coupled to the execution unit 230. Register file 250 is comprised of a group of registers for storing data to be read by the execution unit 230 via the internal bus 270. In one embodiment, the registers within the register file 250 store sixty-four bits of packed data for integer and/or floating point calculations.
The execution unit 230 operates on packed data according to the instructions received by processor 210 that are included in a packed instruction set 240. The execution unit 230 also operates on non-packed data according to instructions implemented in general-purpose processors. In one embodiment the processor 210 is an Explicitly Parallel Instruction Computing (“EPIC”) processor (e.g., employing the IA-64 parallel architecture developed by Intel®), capable of executing multiple instructions per clock cycle. In addition, processor 210 in one embodiment is capable of supporting the Intel Itanium™ microprocessor instruction set as well as the packed instruction set 240. Other instruction sets, such as the Pentium®, PowerPC™ and the Alpha® processor instruction sets may also be used in accordance with the described invention. Pentium and Itanium are trademarks of Intel Corporation. PowerPC™ is a trademark of IBM, APPLE COMPUTER, and MOTOROLA. Alpha™ is a trademark of Digital Equipment Corporation.
Still referring to
In one embodiment, individual extract and deposit instructions are included in the packed instruction set 240. Accordingly, the extract instruction may be used to copy a data element from a source register to an aligned position in a destination register. For example, the instruction EXTR RD=RS, 32, 16 copies a data element 16 bits in length located at bit 32 in the source register (i.e., the LSB of the data element is positioned at bit 32 of the source register) to an aligned position in a destination register as illustrated in
Similarly, a deposit instruction may be used to copy a data element aligned in a source register to a specified position in a destination register. For example, the instruction DEP RD=RD, RS, 16, 32, copies a 16 bit data element aligned in a source register to a position starting at bit 32 (i.e., the LSB of the data element is aligned with bit 32 of the destination register as illustrated in FIG. 4 b). In this embodiment, the RD designation to the right of the equal sign indicates that data elements stored in the remaining bit positions of the destination register should not be overwritten (e.g., with zeros). As described below, this feature allows a series of packed data elements to be merged into a single register.
In one embodiment of the apparatus and method, extract and deposit operations are used to perform “gather” operations in which non-zero data elements of a matrix are retrieved (i.e., “gathered”) from memory and stored in a contiguous manner.
As set forth in the flowchart in
Addresses for each of the data elements are then computed at 520 (
The processor 210, at 530 (
At 540 (
The matrix containing data elements E0–E3 may need to be reconstructed in memory from time to time so that matrix operations can be performed (e.g., matrix multiplication, addition . . . etc). In one embodiment, a “scatter” operation is used to carry out this function. Referring to
At 1030 the data elements are extracted from the register into which they were merged. Thus, as illustrated in
Throughout the foregoing description, for the purposes of explanation, numerous specific details were set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one skilled in the art that the invention may be practiced without some of these specific details. Accordingly, the scope and spirit of the invention should be judged in terms of the claims which follow.
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|Citing Patent||Filing date||Publication date||Applicant||Title|
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|U.S. Classification||711/217, 712/E09.033, 712/5, 712/E09.039, 711/220, 712/4, 712/225|
|Cooperative Classification||G06F9/345, G06F9/30043, G06F9/30036|
|European Classification||G06F9/30A2L, G06F9/30A1P, G06F9/345|
|29 Mar 2000||AS||Assignment|
Owner name: INTEL CORPORATION, CALIFORNIA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:DULONG, CAROLE;REEL/FRAME:010650/0480
Effective date: 20000327
|12 Feb 2010||FPAY||Fee payment|
Year of fee payment: 4
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Year of fee payment: 8