Developer Guide

Contents

Advantages and Limitations of Arbitrary Precision Data Types

Advantages

The arbitrary precision data types have the following advantages over the use of standard C/C++ data types:
  • You can achieve narrower data paths and processing elements for various operations in the circuit.
  • The data types ensure that all operations are carried out in a size guaranteed not to lose any data. However, you can still lose data if you store data in a location where the data type is too narrow in size.

Limitations

AC Data Types
The AC data types have the following limitations:
  • Multipliers are limited to generating 512-bit results.
  • Dividers for
    ac_int
    data types are limited to a maximum of 128-bit unsigned or 127-bit signed.
  • Dividers for
    ac_fixed
    data types are limited to a maximum of 64-bits (unsigned or signed).
  • The
    ac_fixed
    data type currently does not support operations with double-precision floating-point numbers. Cast double values to single-precision floating-point (
    float
    ) when using them with the
    ac_fixed
    data type.
  • The emulation flow does not support using
    ac_int
    and
    hls_float
    data types in
    parallel_for
    kernels.
hls_float
Data Type
The
hls_float
data type has the following limitations:
  • hls_float
    data type is not currently supported on Windows.
  • While the floating-point optimization of converting into constants is performed for
    float
    and
    double
    data types, it is not performed for the
    hls_float
    data type.
  • A limited set of math functions is supported. For details, see Math Functions Supported by hls_float Data Type.
  • Constant initialization works only with the round-towards-zero (
    RZERO
    ) rounding mode.
  • When casting
    hls_float
    data types to integers, only signed integer casts are supported. Casting to unsigned integer simply generates a signed integer cast.

Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.