ESL-CGRA Simulator

This notebook allows you to manage kernels, simulate them and generate assembly files that can the be integrated into the CGRA-X-HEEP flow. This simulator does not include the compilation of C code into CGRA-compatible assembly code. For that purpose refer to SAT-MapIt.

Structure

It is divided into 3 main components:

Utility files

Include the simulator per se and a set of tools to simplify the process of generating, debugging and exporting the results.

Kernel folders

A kernel is a section of an application that wants to be accelerated in the CGRA. Each kernel has a folder with its name. All the files needed to run a simulation should be inside them and follow the naming convention detailed in Creating a kernel. These include (but are not restricted to):

• (optional) A file containing the SAT-MapIt output.
• (optional) A hand-written assembly file.
• An inputs.csv file including the inputs values to the kernel.
• A memory.csv file including the indexed values that the kernel can access indirectly (through a memory address).
• A instructions.csv file containing a matrix of operations to be executed by each Processing Element (PE) during each instruction. This file can be automatically generated from a .out file or hand-written assembly. You may have more than one version of a this file (all named instructions<version>.csv (replacing <version> with any string), but they must use the same environment (inputs and memory).
• A outputs.csv and memory_out.csv files that are generated after every run of the simulator. These files are overriden (even for different versions of the same kerel), so save them somewhere else if you want to keep track of them.

Notebook

An .ipynb is provided to play with the different functionalities of the simulator. You can run actions and see the output directly there.

Usage

The usage of the simulator throught the notebook is very straight-forward.

Creating a kernel

Creating a kernel involves creating a folder with its name and populating it with the necessary files. The module kernels provide some functions to assist in this task.

Folder

To generate a new folder and fill it with empty memory and inputs file call.

kernel_new("<kernel_name>")

Memory

The memory can be easily populated with some patter by calling the function

kernel_add_memory( "<kernel_name>", <address>, <array_of_values> )

The memory.csv file should always have this format

Address	Data
<address 0>	<data 0>
<address 1>	<data 1>
. . .	. . .

Address values do not need to be ordered. When the kernel tries to access a certain address, it will go through the table until it finds it, then return the corresponding data. If the address is not found, -1 is returned (simulating a flash read from an empty address).

When storing information, the kernel will look for the address specified and write in the corresponding data space the value given. If the address is not found, a new line is created containing it.

When using the kernel_add_memory function, overlaps are not considered (i.e. a same memory address might appear more than once in the table, but only the first one will be considered by the simulator -as it will always be found first). Be careful.

Inputs

The inputs file need to be filled manually. Note that there are as many columns as CGRA columns there are. Column 1 of the inputs file will be accessed by column 0 of the CGRA, and so on. The index increments downwards.

Instructions

Instruction files can be generated automatically from the output of SAT-MapIt or a manually-written assembly file following the same structure, or can be created manually editing the .csv file.

It should the same number of columns as the CGRA and only as many rows as instructions + the header of each instruction.

Each instruction is composed as follows (for a $2 \times 2$ CGRA):

<instr. number>
<op. for PE 00>	<op. for PE 01>
<op. for PE 10>	<op. for PE 11>

Notes:

• Always place only the instruction number only in the first column.
• Do not leave empty rows (not even at the end of the file).

The instructions file can be modified to play around with the kernel. If different options want to be considered (using the same input and memory file), the instructions file can be given a version as instruction<version>.csv. When requesting the execution of a kernel, provide the name of the kernel and (optionally) the desired instructions version.

Changing the CGRA size

Currently the CGRA size is hardcoded in the cgra.py module. You can change this value to whatever dimensions you want.

Providing functionality to change this from the notebook interface should be pretty straightforward. If you feel generous today, please open a pull request :)

Running a kernel

Once the whole kernel folder has been filled, you can simply run a simulation by calling the run function of the cgra module:

import cgra
cgra.run("<kernel_name>")

This will provide different outputs

Temporal record

In the output of the notebook a step by step state of each PE's output register is printed until an EXIT instruction is reached. If this instruction was not added, you might very well want to cancel the execution.

Each instruction is divided by dashes and headed by the step number and the instruction being executed (the one found in the instructions file):

Instr = <step number> (<instruction number>)

Each PE in the matrix shows (by default) the value of ROUT after each iteration. For example:

Instr =  8 ( 3 )
[   0,    0,    0,    0]
[   2,    2,    2,    0]
[   3,    3,    3,    0]
[   0,    0,    0,    0]

What is shown in each cell can be modified when calling the run function. For instance calling the function as follows will output the value of R0 instead of ROUT for the kernel convolution in its version _v2 (i.e. will run the instructions from the file convolution/instructions_v2.csv).

run("convolution", version="_v2", pr=["ROUT", "OPS"])

Optional pr parameters include:

Parameter	Description
ROUT (default)	The output register of the PE
R0 - R3	One of the 4 available registers of each P
INST	The full instruction that the cell is executing
OPS	The name of the operation that the cell is executing
[<p1>, <p2>]	An array with any amount of the above parameters

Outputs

Outputs written using the SWD operation are written into an outputs.csv file, where each column represents the output values for each CGRA column. The index increments downwards. This file is overriden on every run.

Memory output

To preserve the memory untouched, a copy of the resulting memory is generated as a memory_out.csv file. This file is overriden on every run.

Exporting the results

Additional notes

• If you make any modification to the utility scripts, you might need to restart the notebook for the changes to apply.