Intel® High Level Synthesis Compiler Standard Edition: Reference Manual

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ID 683310
Date 12/18/2019
Public
Document Table of Contents
Document Table of Contents x
1. Intel® HLS Compiler Standard Edition Reference Manual 2. Compiler 3. C Language and Library Support 4. Component Interfaces 5. Component Memories (Memory Attributes) 6. Loops in Components 7. Component Concurrency 8. Arbitrary Precision Math Support 9. Component Target Frequency 10. Intel® High Level Synthesis Compiler Standard Edition Compiler Reference Summary A. Supported Math Functions B. Intel® HLS Compiler Standard Edition Reference Manual Archives C. Document Revision History of the Intel® HLS Compiler Standard Edition Reference Manual
2. Compiler x
2.1. Intel® HLS Compiler Standard Edition Command Options 2.2. Using Libraries in Your Component 2.3. Compiler Interoperability 2.4. Intel® HLS Compiler Pipeline Approach
3. C Language and Library Support x
3.1. Supported C and C++ Subset for Component Synthesis 3.2. C and C++ Libraries 3.3. Intel® HLS Compiler Standard Edition Compiler-Defined Preprocessor Macros
4. Component Interfaces x
4.1. Component Invocation Interface 4.2. Avalon® Streaming Interfaces 4.3. Avalon® Memory-Mapped Master Interfaces 4.4. Slave Interfaces 4.5. Component Invocation Interface Arguments 4.6. Unstable and Stable Component Arguments 4.7. Global Variables 4.8. Structs in Component Interfaces 4.9. Reset Behavior
4.1. Component Invocation Interface x
4.1.1. Scalar Parameters 4.1.2. Pointer and Reference Parameters 4.1.3. Interface Definition Example: Component with Both Scalar and Pointer Arguments
4.3. Avalon® Memory-Mapped Master Interfaces x
4.3.1. Memory-Mapped Master Testbench Constructor 4.3.2. Implicit and Explicit Examples of Describing a Memory Interface
4.4. Slave Interfaces x
4.4.1. Control and Status Register (CSR) Slave 4.4.2. Slave Memories
5. Component Memories (Memory Attributes) x
5.1. Static Variables
6. Loops in Components x
6.1. Loop Initiation Interval (ii Pragma) 6.2. Loop-Carried Dependencies (ivdep Pragma) 6.3. Loop Coalescing (loop_coalesce Pragma) 6.4. Loop Concurrency (max_concurrency Pragma) 6.5. Loop Unrolling (unroll Pragma)
7. Component Concurrency x
7.1. Serial Equivalence within a Memory Space or I/O 7.2. Concurrency Control (hls_max_concurrency Attribute)
8. Arbitrary Precision Math Support x
8.1. Declaring ac_int Data Types 8.2. Integer Promotion and ac_int Data Types 8.3. Debugging Your Use of the ac_int Data Type 8.4. Declaring ac_fixed Data Types 8.5. AC Data Types and Native Compilers
8.1. Declaring ac_int Data Types x
8.1.1. Important Usage Information on the ac_int Data Type
10. Intel® High Level Synthesis Compiler Standard Edition Compiler Reference Summary x
10.1. Intel® HLS Compiler Standard Edition i++ Command-Line Arguments 10.2. Intel® HLS Compiler Standard Edition Header Files 10.3. Intel® HLS Compiler Standard Edition Compiler-Defined Preprocessor Macros 10.4. Intel® HLS Compiler Standard Edition Keywords 10.5. Intel® HLS Compiler Standard Edition Simulation API (Testbench Only) 10.6. Intel® HLS Compiler Standard Edition Component Memory Attributes 10.7. Intel® HLS Compiler Standard Edition Loop Pragmas 10.8. Intel® HLS Compiler Standard Edition Component Attributes 10.9. Intel® HLS Compiler Standard Edition Component Default Interfaces 10.10. Intel® HLS Compiler Standard Edition Component Invocation Interface Arguments 10.11. Intel® HLS Compiler Standard Edition Component Macros 10.12. Intel® HLS Compiler Standard Edition Streaming Input Interfaces 10.13. Intel® HLS Compiler Standard Edition Streaming Output Interfaces 10.14. Intel® HLS Compiler Standard Edition Memory-Mapped Interfaces 10.15. Intel® HLS Compiler Standard Edition Arbitrary Precision Data Types
A. Supported Math Functions x
A.1. Math Functions Provided by the math.h Header File A.2. Math Functions Provided by the extendedmath.h Header File A.3. Math Functions Provided by the ac_fixed_math.h Header File
1. Intel® HLS Compiler Standard Edition Reference Manual
2. Compiler
3. C Language and Library Support
4. Component Interfaces
5. Component Memories (Memory Attributes)
6. Loops in Components
7. Component Concurrency
8. Arbitrary Precision Math Support
9. Component Target Frequency
10. Intel® High Level Synthesis Compiler Standard Edition Compiler Reference Summary
A. Supported Math Functions
B. Intel® HLS Compiler Standard Edition Reference Manual Archives
C. Document Revision History of the Intel® HLS Compiler Standard Edition Reference Manual

10.8. Intel® HLS Compiler Standard Edition Component Attributes

Table 25.   Intel® HLS Compiler Standard Edition Component Attributes Summary
Feature Description
hls_max_concurrency Request more copies of the component memory so that the component can run multiple invocations in parallel.

hls_max_concurrency Component Attribute

Syntax
hls_max_concurrency(<N>)
Description
In some cases, the concurrency of a component is limited to 1. This limit occurs when the generated hardware cannot be shared across component invocations. For example, when using component memories for a non-static variable.

You can use this attribute to request more copies of the component memory so that the component can run multiple invocations in parallel.

This attribute can accept any non-negative whole number, including 0.
Value greater than 0
A value greater than 0 indicates how many copies of the component memory to instantiate as well as how many component invocations can be in flight at once.
Value equal to 0
Setting hls_max_concurrency to a value of 0 is useful in cases when there is no component memory but the component still has a poor dynamic loop initiation interval (II) even if you believe your component II should be 1. You can review the II for loops in your component in the high level design report.

To learn more, review the design example: <quartus_installdir>/hls/examples/inter_decim_filter.

Example 
hls_max_concurrency(2)
component void foo(ihc::stream_in<int> &data_in,
      ihc::stream_out<int> &data_out) {
 int arr[N];
 for (int i = 0; i < N; i++) {
   arr[i] = data_in.read();
 }
 // Operate on the data and modify in place
 for (int i = 0; i < N; i++) {
   data_out.write(arr[i]);
 }
}
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