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GEMV 3: H2D and D2H Memcpy

GEMV 3: H2D and D2H Memcpy

The memcpy functionality of SdkRuntime allows the programmer to copy data between the host and device. Continuing from the previous example, we now extend it to include memcpy_h2d calls which copy data from the host to initialize A, x, and y on device.

Note

See GEMV Tutorial 3: Memcpy for a step-by-step walkthrough of this example.

layout.csl

const memcpy = @import_module("<memcpy_multi/get_params>", .{
  .width = 1,
  .height = 1
});

layout {
  @set_rectangle(1, 1);
  @set_tile_code(0, 0, "pe_program.csl", .{ .memcpy_params = memcpy.get_params(0) });

  // export symbol names
  @export_name("A", [*]f32, true);
  @export_name("x", [*]f32, true);
  @export_name("b", [*]f32, true);
  @export_name("y", [*]f32, false);
  @export_name("init_and_compute", fn()void);
}

pe_program.csl

param memcpy_params: comptime_struct;

const LAUNCH: color = @get_color(8);

// memcpy module provides infrastructure for copying data
// and launching functions from the host
const sys_mod = @import_module("<memcpy_multi/memcpy>", @concat_structs(memcpy_params, .{
  .LAUNCH = LAUNCH
}));

// Constants definining dimensions of our matrix
const M: i16 = 4;
const N: i16 = 6;

// 48 kB of global memory contain A, x, b, y
var A: [M*N]f32; // A is stored row major
var x: [N]f32;
var b: [M]f32;
var y: [M]f32;

// DSDs for accessing A, b, y
// A_dsd accesses column of A
var A_dsd = @get_dsd(mem1d_dsd, .{ .tensor_access = |i|{M} -> A[i*N] });
var b_dsd = @get_dsd(mem1d_dsd, .{ .tensor_access = |i|{M} -> b[i] });
var y_dsd = @get_dsd(mem1d_dsd, .{ .tensor_access = |i|{M} -> y[i] });

// ptrs to A, x, b, y will be advertised as symbols to host
var A_ptr: [*]f32 = &A;
var x_ptr: [*]f32 = &x;
var b_ptr: [*]f32 = &b;
const y_ptr: [*]f32 = &y;

// Compute gemv
fn gemv() void {
  // Loop over all columns of A
  for (@range(i16, N)) |i| {
    // Calculate contribution to A*x from ith column of A, ith elem of x
    @fmacs(y_dsd, y_dsd, A_dsd, x[i]);
    // Move A_dsd to next column of A
    A_dsd = @increment_dsd_offset(A_dsd, 1, f32);
  }
  // Add b to A*x
  @fadds(y_dsd, y_dsd, b_dsd);
}

// Call initialize and gemv functions
fn init_and_compute() void {
  gemv();
  sys_mod.unblock_cmd_stream();
}

comptime {
  @export_symbol(A_ptr, "A");
  @export_symbol(x_ptr, "x");
  @export_symbol(b_ptr, "b");
  @export_symbol(y_ptr, "y");
  @export_symbol(init_and_compute);
  @rpc(LAUNCH);
}

run.py

#!/usr/bin/env cs_python

import argparse
import numpy as np

from cerebras.sdk.runtime.sdkruntimepybind import SdkRuntime, MemcpyDataType, MemcpyOrder # pylint: disable=no-name-in-module

# Read arguments
parser = argparse.ArgumentParser()
parser.add_argument('--name', help="the test compile output dir")
parser.add_argument('--cmaddr', help="IP:port for CS system")
args = parser.parse_args()

# Matrix dimensions
M = 4
N = 6

# Construct A, x, b
A = np.arange(M*N, dtype=np.float32)
x = np.full(shape=N, fill_value=1.0, dtype=np.float32)
b = np.full(shape=M, fill_value=2.0, dtype=np.float32)

# Calculate expected y
y_expected = A.reshape(M,N)@x + b

# Construct a runner using SdkRuntime
runner = SdkRuntime(args.name, cmaddr=args.cmaddr)

# Get symbols for A, b, x, y on device
A_symbol = runner.get_id('A')
x_symbol = runner.get_id('x')
b_symbol = runner.get_id('b')
y_symbol = runner.get_id('y')

# Load and run the program
runner.load()
runner.run()

# Copy A, x, b to device
runner.memcpy_h2d(A_symbol, A, 0, 0, 1, 1, M*N, streaming=False,
  order=MemcpyOrder.ROW_MAJOR, data_type=MemcpyDataType.MEMCPY_32BIT, nonblock=False)
runner.memcpy_h2d(x_symbol, x, 0, 0, 1, 1, N, streaming=False,
  order=MemcpyOrder.ROW_MAJOR, data_type=MemcpyDataType.MEMCPY_32BIT, nonblock=False)
runner.memcpy_h2d(b_symbol, b, 0, 0, 1, 1, M, streaming=False,
  order=MemcpyOrder.ROW_MAJOR, data_type=MemcpyDataType.MEMCPY_32BIT, nonblock=False)

# Launch the init_and_compute function on device
runner.launch('init_and_compute', nonblock=False)

# Copy y back from device
y_result = np.zeros([M], dtype=np.float32)
runner.memcpy_d2h(y_result, y_symbol, 0, 0, 1, 1, M, streaming=False,
  order=MemcpyOrder.ROW_MAJOR, data_type=MemcpyDataType.MEMCPY_32BIT, nonblock=False)

# Stop the program
runner.stop()

# Ensure that the result matches our expectation
np.testing.assert_allclose(y_result, y_expected, atol=0.01, rtol=0)
print("SUCCESS!")

commands.sh

#!/usr/bin/env bash

set -e

cslc ./layout.csl --fabric-dims=8,3 \
--fabric-offsets=4,1 -o out --memcpy --channels 1
cs_python run.py --name out

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GEMV 2: Memory DSDs

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GEMV 4: Parameters