CGRAs

CGRAs (Coarse-Grained Reconfigurable Architectures) are arrays of interconnected Processing Elements (PEs) arranged in a mesh style, offering a blend of hardware performance and software flexibility. In this architecture, each PE consists of a Cell Processing unit containing a Functional Unit (FU) surrounded by configurable routing logic. By mapping graph nodes to the FUs and configuring routing logic to establish connections between them based on the graph edges, the overlay executes a given Data Flow Graph (DFG). This overlay architecture operates on a data-driven execution model, where an FU performs an operation only when its inputs are ready and its output is available. Inputs are located in the north and outputs can be obtained from the east.

Architecture

Overlay

Processing Element

Elastic Buffer

Benchmarks

Name	Inputs	Outputs	Expression
Sum	2 Arrays	1 Array	x[i] = a[i] + b[i]
Accumulate	2 Arrays	1 Array, 1 Scalar	c[i] = c[i] (a[i] + b[i]) , x = x + ∑ c[i]
Cap	2 Arrays	1 Array	(((a[i] * 6) >> 2) * 2) * (((b[i] * 3 * a[i])>>2) * a[i]);
Mac	2 Arrays, 1 Scalar	1 Scalar	x = x + ∑ a[i] b[i]
Mac2	4 Arrays, 2 Scalars	2 Scalars	x = x + ∑ a[i] b[i] , y = y + ∑a[i] (b[i] + 1)c[i] d[i]

Building on Ubuntu

1. Install gtkwave: $ sudo apt-get -y install gtkwave

2. Clone the repository.

3. Use the Makefile to run the tests. For example, $ make test_name where test_name can be:

   • alu-test
   • fu-test
   • join-test
   • d-eb-test
   • d-reg-test
   • fs-test
   • fr-test
   • conf-mux-test
   • d-fifo-test
   • cell-processing-test
   • processing-element-test
   • overlay-sum
   • overlay-cap
   • overlay-acc
   • overlay-mac
   • overlay-mac2

4. The VCD files are generated in the test_run_dir folder.

5. You can check the inputs and results of the benchmarks in the following table:

Benchmark	a	b	c	d	x	y	Result	Result
SUM	North East	Middle North OV 3					North East (x)
ACC	North East	North West	Middle North OV 2		Middle North OV 3		North East (c)	Middle East OV 1 (x)
CAP	North West	North East						Middle East OV 2 (x)
MAC	Middle North OV 2	Middle North OV 3			North East		North East (x)
MAC 2	Middle North OV	North West	Middle North OV 1	Middle North OV 2	Middle North OV 3	North East	North East (y)	Middle East OV (x)