Range

Range represents a sequence of 32b integer values from a given start (inclusive) to end (exclusive) with a non-zero step size. Range also has an optional parallelization factor, which is used to determine physical unrolling in hardware.

In Accel scopes, Range instances can be implicitly converted to Counter.

Ranges can be created using two different syntax flavors. When unspecified, the default value for start is 0, and the default value for step and par are both 1.

Form 1:

val range1 = max by step        // start of 0, step by 1, parallelization of 1
val range2 = start until max    // start of 0, step by 1, parallelization of 1
val range3 = start until max by step par p

Form 2:

val range4 = start :: end       // Step of 1, parallelization of 1
val range5 = start :: step :: end par p

Form 1 is typically used for specifying the domain of a loop, while Form 2 is used for Matlab-like syntax when selecting a range of elements from a memory.

Ranges can also be used to create Scala-like for loops on the CPU::

for (i <- 0 until max by 2) {
    ..
}

This loop will run for all even integers from [0, max). Note that this syntax is only usable on the CPU or in simulation.

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Infix methods

class Range
def length: Index Returns the length of this Range.
def by(step: Index): Range Creates a Range with this Range’s start and end but with the given step size.
def par(p: Index): Range Creates a Range with this Range’s start, end, and stride, but with the given par parallelization factor.
def ::(start2: Index): Range Creates a Range with this Range’s end, with the previous start as the step size, and the given start. Note that this operator is right-associative.
def foreach(func: Index => Unit): Unit Iterates over all integers in this range, calling func on each. NOTE: This method is unsynthesizable, and can be used only on the CPU or in simulation.

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Implicit methods

def rangeToCounter(range: Range): Counter Implicitly creates a hardware Counter from this Range.