# Patent

## Title
Router

## Abstract

Configuration of a reconfigurable multidimensional field may include prioritizing required connections between cells, establishing connections having a high priority first, and establishing additional connections after the high priority connections have been established.

## Background
FIELD OF THE INVENTION
The present invention relates to configurable modules and the like, in particular the management of data streams therein, in particular with the placement of resources and routing of connections between cells, etc.
BACKGROUND INFORMATION
Multidimensional fields of data processing cells are already known. The generic class of these modules includes in particular systolic arrays, neural networks, multiprocessor systems, processors having a plurality of arithmetic units and/or logic cells and/or communicative/peripheral cells (IO), interconnection and network modules such as crossbar switches as well as known modules of the generic types FPGA, DPGA, Chameleon, XPUTER, etc. In particular there are known modules in which first cells are reconfigurable during run time without interfering with the operation of other cells (see, for example, German Patent No. 44 16 881, German Patent Application Nos. DE 197 81 412.3, DE 197 81 483.2, DE 196 54 846.2-53, DE 196 54 593.5-53, DE 197 04 044.6-53, DE 198 80 129.7, DE 198 61 088.2-53, and DE 199 80 312.9, International Application No. PCT/DE 00/01869, German Patent Application Nos. DE 100 36 627.9-33, DE 100 28 397.7, DE 101 10 530.4, and DE 101 11 014.6, International Application No. PCT/EP 00/10516, and European Application No. EP 01 102 674.7). These are herewith incorporated fully into the present text for disclosure purposes. Reference is also made to the Chameleon system processor architecture. However, the usability of the structure mentioned last for data processing purposes is more comparable to an arrangement described in German Patent Application No. DE 101 03 624.
The data processing cells of these modules may now execute different functions such as Boolean and/or arithmetic operations on input operands. Connections running between the cells are also adjustable and typically include buses capable of interconnecting in various ways and thus creating a multidimensional field whose interconnection is adjustable. The cells exchange information such as status signals, triggers or the data to be processed over the buses or other lines. The cells are typically arranged in rows and columns in a two-dimensional processor field, with the outputs of cells of a first row being connected to buses to which the inputs of cells of the next row are also to be connected. In a conventional design (Pact XPP), forward and backward registers are also provided for carrying data while bypassing cells on bus systems of other rows, achieving a balance of branches to be executed simultaneously, etc. There have already been proposals for providing such forward and/or backward registers with a functionality that goes beyond pure data transfer.
In general, however, it is necessary to define which cell performs which data processing steps, where this cell is situated and how it is connected. In the related art, strategies for automatic control of placement mechanisms and routing mechanisms are already known.
Placers, for example, typically operate according to a force method, which uses forces between cells for optimum placement of dependent cells by simulating connections by springs in a physical model. This usually yields a mostly suitable placement result.
In addition, German Patent No. 44 16 881, and German Patent Application Nos. DE 196 54 846.2-53 and DE 102 06 653.1 describe data processing methods for reconfigurable modules in which data is read out of one or more memories in each processing step and is then processed and written to one or more memories. According to the related art, the read and write memories are placed differently and are typically placed in opposition (FIGS. xxua, xxub, xxuc and German Patent Application No. DE 102 06 653.1, FIG. 3).
Special reconfiguration methods (wave reconfiguration) are also described in German Patent Application Nos. DE 197 04 728.9, DE 199 26 538.0, DE 100 28 397.7 for the aforementioned modules, thus permitting particularly efficient reconfiguration by jointly transmitting the reconfiguration information together with the last data to be processed via the data buses and/or trigger buses, and by reconfiguring the buses and cells immediately after successful processing.
To perform a certain type of data processing, each cell must be assigned a certain function and at the same time a suitable position in space and interconnection must be provided. Therefore, before the multidimensional processor field processes data as desired, it is necessary to ascertain which cell is to execute which function; a function must be defined for each cell involved in a data processing task, and the interconnection must be determined.
SUMMARY
An object of the present invention is to provide a novel embodiment for commercial use.
First, a method for creating configurations for multidimensional fields of reconfigurable cells for implementing given applications in which an application is broken down into individual modules and the elements necessary for performing this method are placed module by module. Such a breakdown into modules is advantageous, because then configurations may be determined more easily for these modules.
It may be particularly preferable if stationary elements are provided in at least one module in the method and these stationary elements are provided at predetermined locations and the non-fixed elements are subsequently placed. It is then possible to place modules among the individual mobile and/or immobile objects by minimizing assigned virtual forces.
Generally, it may also be desirable to arrange the function and interconnection in such a way that data processing may be performed as promptly as possible and with the best possible use of resources. Frequently however, e.g., due to hardware restrictions, it is impossible to find an arrangement that will ensure the desired data transfer in an optimum manner. Suboptimal arrangements must then be used.
It is now further proposed according to the present invention that, to improve the configuration for multidimensional fields of reconfigurably interconnected data processing cells, the required connections between the cells be prioritized, with connections having a high priority being established first and other connections being established subsequently.
This minimizes the use of suboptimal configurations due to the fact that it ensures that data having fewer restrictions due to a shortage of resources, such as a limited number of buses, etc., may stream over connections that are particularly important, e.g., due to a required high low latency time, etc.
It is therefore also preferably possible for connections to be prioritized, taking into account in particular an allowable delay in data processing. Prioritization may be performed by taking into account the maximum allowed delay and/or delay ratios of different connections. Delay ratios to be taken into account in prioritization preferably include a delay of “0,” “longer than,” “longer than or equal to” and “equal to.”



BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1a and 1b show PAE cells of an XPP architecture flanked by forward and backward registers.
FIG. 2 shows how data from an output port converges at a node and how this may happen at an input of a cell.
FIG. 3 shows how data converges at a node.
FIG. 4 shows how data converges at a node.
FIGS. xxua-xxuc show the direction of data flow of each successive configuration changes.
FIGS. xxva-xxvc an example of a plurality of arrangements for two reconfiguration cycles.
FIGS. xxwa-xxwc show corresponding arrangements from several sides of the array may also be used at the same time; two corresponding reconfiguration cycles are illustrated.
FIG. xxsa shows that after each processing of a last data word, the next following configuration may be set immediately; only after reconfiguration of all the cells and buses involved is it possible to begin with the next data processing.
FIG. xxsb shows largely maintaining the direction of flow between the cells and merely exchanging the bus systems of the memories.
FIG. xxta shows memories for reading data and writing data situated close together.
FIG. xxtb shows that in performing a reconfiguration, only the bus systems between the read/write memories are exchanged.
FIG. xxxa shows the introduction of registers into the long feedback buses at regular intervals.
FIG. xxxb shows all the cells of a loop arranged as locally as possible around a loop head; the loop foot is placed as close to the loop head as possible.
FIG. xxxc shows a helical arrangement.
FIG. xxxd shows all the cells of a loop arranged as locally as possible around a loop head; the loop foot is placed as close to the loop head as possible.
FIG. xxxe shows a wave-shaped pattern.
FIG. xxxf shows a long feedback bus.
FIG. xxxg shows a coil.
FIG. xxxh shows rolling out a loop in three directions.



DETAILED DESCRIPTION
The connections among the cells of a configuration are produced by defining a boundary around cells and attempting first to connect the cells by connections within the boundary around cells. This is demonstrated with respect to FIGS. 1a and b, where the PAE cells of an XPP architecture of the present applicant are shown as elongated and flanked by forward and backward registers labeled as “FR” and “BR,” respectively. A field part is delimited by a dotted line depicting the boundary. A route search will typically progress from the starting cell to the target cell only in the X direction, i.e., horizontally, and then if no more progress is possible in one row in the X direction, e.g., because no more suitable buses are available, then the row is switched to the Y direction. FIG. 1b shows an example of a possible connecting line when a direct connection is no longer possible between given cells.
It is possible that if all the required connections cannot be established within the boundary, a connection may be established outside of the boundary. If another connection cannot be established as needed, then in both cases, i.e., inside or outside, an existing connection should be severed and the additional connection established, whereupon an attempt is made to provide a replacement for the severed connection. However, it may be preferable to wait before going beyond the boundary until it is certain that no additional connections are establishable within the boundary even by disconnecting others.
It is possible to provide connections on which a plurality of outputs are combined and are connected to a plurality of inputs, a connection being established in such a way that a path segment separates the input nodes and the output splits. This is illustrated in FIGS. 2 through 4, which show possible allowed and unallowed connections. FIG. 2 shows in general how data from an output port, i.e., an output terminal, converges at a node (arrow A) and how this may happen at an input of a cell (arrow B). FIG. 2 thus shows possibilities for different paths along with data may run from object B (cell) at the top right to a lower object. The lower object may be, for example, a PAE, an IOPAE, etc. FIGS. 3 and 4 show how data converges in an allowed manner at nodes (FIG. 3) because a single path segment is provided between output splits (outport splits) and input nodes (inport joins) between each route.
It is preferable if, after establishing the connections, the maximum latency time of the configuration is determined and/or a maximum frequency corresponding to it for the configuration operation is determined. This information may be used to evaluate the quality of the configuration result and/or for data processing using the configuration.
It is also preferable if, after determining all signal propagation paths along all connections, a propagation-time equalization is performed for signals converging at nodes. In the applicant's XPP technology, for which the present application is particularly preferred, this is possible by providing register stages which may be inserted into the connecting pathways in particular in changing the cell row. First, a connection to the register may be established and then the register number required for balancing is determined. This procedure is particularly advantageous in placement and routing.
In the related art there is still occasionally a problem which it would be advantageous to at least partially relieve in certain situations. Namely, the automatically created placement for feedback, i.e., for program loops, for example, in which data from a downstream cell to a cell which has previously processed data is frequently so inefficient that the feedback must go too far, i.e., the feedback bus is too long (FIG. xxxf). In other words, the sender and receiver of feedback are too far apart. This greatly reduces the processing frequency of reconfigurable modules.
It is desirable now to create a possibility for improving the arrangement and/or interconnection of cells and/or modules containing cells.
A first approach according to the present invention creates an expedient here by introducing registers (R) into the long feedback buses at regular intervals (FIG. xxxa), resulting in a type of pipelining and increasing the clock pulse frequency accordingly, because the transmission times between registers are much shorter than the transmission time directly from the sender to the receiver. However, this method results in a considerable latency time, which in turn greatly reduces the processing performance, in particular in loops.
For wave reconfiguration, it is also possible to provide particularly efficient data processing when a second reconfiguration may be configured immediately after processing the last data word of a first configuration (i.e., in the same cycle or in a cycle shortly following that one) and the first data word of the second configuration is processed immediately thereafter (i.e., in the same cycle or in a cycle which follows that one shortly).
According to FIGS. xxua-xxuc, however, the direction of data flow of each successive configuration changes. Thus, after each processing of a last data word, the next following configuration may be set immediately, but only after reconfiguration of all the cells and buses involved is it possible to begin with the next data processing (FIG. xxsa). An approach according to the present invention thus involves largely maintaining the direction of flow between the cells and merely exchanging the bus systems of the memories (FIG. xxsb). However, this again results in the problem of long run times and low clock pulse rates as described above in conjunction with feedbacks. Here again, as described already, registers which would result in an increase in clock pulse frequency might be introduced. At the same time, however, this would result in a substantial latency time which is in turn undesirable.
In a preferred variant, feedback loops with data streaming through registers are therefore avoided.
It has been found that particularly good results may be achieved when all the cells of a loop are arranged as locally as possible around a loop head (SK), and in particular the loop foot (SF) is placed as close to the SK as possible (FIGS. xxxb, xxxd). A helical arrangement resembling the symbol @ (FIG. xxxc) is also optimal.
It is therefore proposed that for configuration and/or reconfiguration of a multidimensional field and/or cells for data processing in which data is processed in cells, processing results be sent to cells downstream to be processed further there, data being sent from at least one cell downstream to at least one cell upstream, in such a way that the cell position is determined so that the downstream cell is positioned so close to the upstream cell that the feedback time of this connection is not longer than that of any other connection in the configuration.
This may typically be achieved by arranging the downstream cells closer than one-fourth of the total data streaming path in the case of the upstream cell.
This may be achieved particularly well when the cells having the densest data are situated between the upstream end and the downstream end in the form of a coil or in a wave-shaped pattern.
There are various possibilities now for achieving such a feedback loop minimization.
Placements may thus be performed while minimizing virtual forces between cells and other objects, and then the feedback loop minimization is achieved, for example, by introducing another “virtual” spring force from each element of a loop to the loop head (SK) and/or the loop foot (SF). Alternatively and/or additionally, a virtual force may be provided between the loop foot and the loop head. This virtual spring force does not represent a bus connection but instead is used only to achieve the placement arrangement according to the present invention. In particular, the virtual spring force may be different from the spring force of bus connections that actually exist. Other methods of automatically generating the placement arrangement will then be obvious to those skilled in the art in accordance with the particular placement principle.
For very large loops, the cells of the loop are arranged in a wave-shaped pattern around the SK and/or SF (FIG. xxxe) or they are wound around the SK and/or SF, but a wave-shaped arrangement is preferred.
A coil may be achieved by reducing the “virtual” spring forces linearly or uniformly in steps over the length of the loop. FIG. xxxg shows a corresponding example in which the spring forces are reduced incrementally. Coils have the problem that they result in relatively long buses to the core of the coil (SK, SF).
The preferred wave-shaped arrangement may be achieved by assigning periodically higher and lower “virtual” spring forces to SK and/or SF to the particular cells of the loop. For example, such an assignment may be made by a sine function or a quasi-sine function. Such periodic “virtual” spring forces (0, 1, 2, 3) are shown as an example in FIG. xxxe. The periods, i.e., the frequency of the sine function, should be determined optimally so that the first cell after the SK and the last cell before the SF (or the SF itself) have the maximum possible spring force to position them as close together locally as possible. Due to the placement while defining a virtual winding force, different tasks may be configured and/or placed.
Thus, in principle methods may be used which provide for the cell position in a field having cells of selectable function to be determined by minimization of virtual forces on the cells, virtual forces different from zero being provided between the upstream cell and the downstream cell (SF, SK). A memory, in particular a multiport memory, may be provided in the path between the upstream cell and the downstream cell in particular.
Thus, a corresponding method may now be used for optimization of wave reconfiguration. First, it is stipulated that the memories for reading data and writing data are not located on the opposite sides of an array of cells but instead are situated as close together as possible locally according to SK and SF (FIG. xxta). In performing a reconfiguration, only the bus systems between the read/write memories need be exchanged. The buses are therefore only minimally longer, if at all, but this does not result in any considerable impairment of the clock pulse frequency (FIG. xxtb). Further optimization may be achieved by using the same memories for reading the data (operands) and for writing the results, although different memory banks or different read/write pointers in FIFO-like memories are used, for example, and preferably multiport memories are used, permitting simultaneous access to multiple ports. In such a preferred variant, switching the bus systems is also eliminated, because one and the same memory is used.
Using this principle, the direction of data flow does not change in comparison with the wave reconfiguration running direction, which yields optimum performance.
Within an array, a plurality of these arrangements may be implemented at the same time. This is shown in FIGS. xxva-xxvc as an example for two reconfiguration cycles. Likewise, corresponding arrangements from several sides of the array may also be used at the same time. FIGS. xxwa-xxwc show two corresponding reconfiguration cycles as an example.
The method according to FIG. xxx is particularly efficient when the requirements of wave reconfiguration are also taken into account in such a way that SK and/or SF, for example, are to be situated as close as possible locally to a memory (RAM). This is possible, e.g., by rolling out the loop in only three directions (FIG. xxxh), and this is in turn achieved through a suitable periodic buildup of the “virtual” spring forces. Depending on whether the spring forces are built up or reduced uniformly, different arrangements may be achieved. The example shown in FIG. xxxh uses a uniform linear slow buildup and a rapid linear reduction.

## Claims

1. A method of configuring a multidimensional field of reconfigurable interconnected data processing cells, the method comprising:
prioritizing required connections between the data processing cells;
establishing connections having a high priority first; and
establishing additional connections after the connections having the high priority have been established.

2. The method as recited in claim 1, wherein the connections are prioritized by taking into account an acceptable delay in data processing.

3. The method as recited in claim 1, further comprising:
defining a boundary around a subset of the data processing cells; and
attempting first to connect the subset of data processing cells via connections within the boundary.

4. The method as recited in claim 3, wherein, when it is impossible to provide all necessary connections within the boundary, establishing a connection outside of the boundary.

5. The method as recited in claim 3, wherein, when it is impossible to establish an additional connection as necessary, a connection that has already been established is disconnected and the additional connection is established, whereupon an attempt is made to provide a replacement for the connection that has been disconnected.

6. The method as recited in claim 1, further comprising:
establishing connections on which a plurality of outputs are combined and which are connected to a plurality of inputs, a connection being established in such a way that a spacer separates input nodes and output splits.

7. The method as recited in claim 1, wherein, after establishing the connections, at least one of: i) a maximum latency time of a configuration is determined, and ii) a maximum corresponding frequency for the configuration is determined.

8. The method as recited in claim 7, wherein prioritization is performed by taking into account at least one of a maximum allowed delay and delay ratios of different connections.

9. The method as recited in claim 8, wherein delay relationships in prioritization take into account a delay of “0, ” “longer than, ” “longer than or equal to” and “equal to. ”

10. The method as recited in claim 1, wherein, after defining all signal travel paths along all connections, a propagation-time equalization is performed for signals converging at nodes.

11. A method for establishing connections between cells of a multidimensional field of reconfigurable data processing cells, the method comprising:
defining a boundary around the cells;
attempting first to connect the cells via a connection within the boundary; and
only if connection of the cells via any connections within the boundary is impossible, establishing a connection outside the boundary for connecting the cells.