Description
Important:
syn.directive.array_partition
and syn.directive.array_reshape
are not supported for
M_AXI
Interfaces on the top-level function.
Instead you can use the hls::vector
data types as
described in the Vector Data Types section of the Vitis
High-Level Synthesis User Guide (UG1399).
syn.directive.array_partition
partitions an array
into smaller arrays or individual elements.
This partitioning:
- Results in RTL with multiple small memories or multiple registers instead of one large memory
- Effectively increases the number of read and write ports for the storage
- Potentially improves the throughput of the design
- Requires more memory instances or registers
Syntax
syn.directive.array_partition=[OPTIONS] <location> <array>
-
<location>
is the location (in the formatfunction[/label]
) which contains the array variable. -
<array>
is the array variable to be partitioned.
Options
-
dim=<integer>
- Specifies which dimension of the array is to be
partitioned.
- The dimension is relevant for multi-dimensional arrays only.
- If a value of 0 is used, all dimensions are partitioned with the specified options.
- Any other value partitions only that dimension. For example, if a value 1 is used, only the first dimension is partitioned.
-
type=(block|cyclic|complete)
-
-
block
partitioning creates smaller arrays from consecutive blocks of the original array. This effectively splits the array into N equal blocks where N is the integer defined by the-factor
option. -
cyclic
partitioning creates smaller arrays by interleaving elements from the original array. For example, if-factor 3
is used:- Element 0 is assigned to the first new array.
- Element 1 is assigned to the second new array.
- Element 2 is assigned to the third new array.
- Element 3 is assigned to the first new array again.
-
complete
partitioning decomposes the array into individual elements. For a one-dimensional array, this corresponds to resolving a memory into individual registers. For multi-dimensional arrays, specify the partitioning of each dimension, or use-dim 0
to partition all dimensions.
complete
. -
-
factor=<integer>
- Used for
block
orcyclic
partitioning only, this option specifies the number of smaller arrays that are to be created. -
off=true
- Disables the ARRAY_PARTITION feature for the specified
variable. Does not work with
dim
,factor
, ortype
.
Example 1
Partitions array AB[13] in function func
into four arrays. Because four is not an integer factor of
13:
- Three arrays have three elements.
- One array has four elements (AB[9:12]).
syn.directive.array_partition=func AB type=block factor=4
Partitions array AB[6][4] in function func
into two arrays, each of dimension [6][2].
syn.directive.array_partition=func AB type=block factor=2 dim=2
Partitions all dimensions of AB[4][10][6] in function func
into individual elements.
syn.directive.array_partition=func AB type=complete dim=0
Example 2
Partitioned arrays can be addressed in your code by the new
structure of the partitioned array, as shown in the following code example. When
using the following
directive:
syn.directive.array_partition=top b type=complete dim=1
The code can be structured as follows:
struct SS
{
int x[N];
int y[N];
};
int top(SS *a, int b[4][6], SS &c) {...}
syn.directive.interface mode=ap_memory top b[0]
syn.directive.interface mode=ap_memory top b[1]
syn.directive.interface mode=ap_memory top b[2]
syn.directive.interface mode=ap_memory top b[3]