Preallocating Buffers with @print_buffer_usage

The @print_buffer_usage macro in Buffers.jl is a useful tool for determining the memory requirements of a buffer within a given block of code. This allows you to preallocate the buffer with the appropriate size, ensuring efficient memory usage and avoiding unnecessary reallocations.

Usage

To use the @print_buffer_usage macro, simply wrap your code block with the macro and specify the buffer(s) you want to analyze. The macro will print the function body to determine the peak memory usage of the buffer(s) within the code block.

Example

using Buffers

buf = Buffer(100000)
@print_buffer_usage buf begin
  if small
    A = alloc!(buf, 10, 10, 20)
  else
    A = alloc!(buf, 10, 10, 30)
  end
  B = alloc!(buf, 10, 10, 10)
  if small
    C = alloc!(buf, 10, 20)
  else
    C = alloc!(buf, 10, 30)
  end
  rand!(B)
  rand!(C)
  An = neuralyze(A)
  @tensor An[i,j,k] = B[i,j,l] * C[l,k]
  drop!(buf, B, C)
  reset!(buf)
end

In this example, the @print_buffer_usage macro will analyze the memory usage of the buffer buf within the code block and print the body of the function which can be used to preallocate the buffer with the appropriate size based on the peak memory usage. All function calls with the buffer buf will be replaced with pseudo_<function-name>. The pseudo_alloc!, pseudo_drop!, and pseudo_reset! functions are predefined, and you have to define your own pseudo_functions if necessary.

# Function to calculate length for buffer(s) buf
# autogenerated by @print_buffer_usage
=============================================
quote
    buf = [0, 0]
    if small
        A = pseudo_alloc!(buf, 10, 10, 20)
    else
        A = pseudo_alloc!(buf, 10, 10, 30)
    end
    B = pseudo_alloc!(buf, 10, 10, 10)
    if small
        C = pseudo_alloc!(buf, 10, 20)
    else
        C = pseudo_alloc!(buf, 10, 30)
    end
    pseudo_drop!(buf, B, C)
    pseudo_reset!(buf)
    return buf[2]
end
=============================================

Wrap the autogenerated function body to a function and use it to preallocate the buffer with the correct size.

function preallocate_buffer(small)
    buf = [0, 0]
    if small
        A = pseudo_alloc!(buf, 10, 10, 20)
    else
        A = pseudo_alloc!(buf, 10, 10, 30)
    end
    B = pseudo_alloc!(buf, 10, 10, 10)
    if small
        C = pseudo_alloc!(buf, 10, 20)
    else
        C = pseudo_alloc!(buf, 10, 30)
    end
    pseudo_drop!(buf, B, C)
    pseudo_reset!(buf)
    return buf[2]
end

buf = Buffer(preallocate_buffer(true))

Multiple Buffers

The @print_buffer_usage macro can also be used with multiple buffers. Simply list the buffers you want to analyze before the code block.

using Buffers

buf1 = Buffer(100000)
buf2 = Buffer(50000)
@print_buffer_usage buf1 buf2 begin
    A = alloc!(buf1, 10, 10, 20)
    B = alloc!(buf2, 20, 5)
    rand!(A)
    rand!(B)
    drop!(buf1, A)
    drop!(buf2, B)
    reset!(buf1)
    reset!(buf2)
end

This will print the peak memory usage for both buf1 and buf2.

By using the @print_buffer_usage macro, you can ensure that your buffers are preallocated with the correct size, leading to more efficient memory management and improved performance in your applications.