Topic 5: Sentinels
Contents
Topic 5: Sentinels¶
In previous programs, we used so-called routable colors, which are associated with a route to direct the flow of wavelets. On WSE-2, task IDs which can receive data wavelets are in the range 0 through 23, corresponding to the IDs of the colors. On WSE-3, task IDs which can receive data wavelets are in the range 0 through 7, corresponding to input queues which are bound to a routable color. We have also used local tasks, which on WSE-2 can be associated with any task ID from 0 to 30, and on WSE-3 can be associated with any task ID from 8 to 30.
This example demonstrates the use of a non-routable control task ID to signal the end of an input tensor. We call this use for a control task ID a sentinel.
In this example, the host sends to a receiving PE (sentinel.csl) the number
of wavelets that the receiving PE should expect to receive, followed by the
stream of data.
The receiving PE then sends the data to its neighbor (pe_program.csl),
followed by a control wavelet which specifies the control task ID that the
neighbor will activate.
Since sentinel control task IDs are not routable colors, the programmer does
not specify a route, but does need to bind the control task ID to a control
task, which will be activated upon receipt of the sentinel wavelet.
Here, the sentinel activates the send_result task, which relays the
result of the sum reduction back to the host.
layout.csl¶
// Color map
//
// ID var ID var ID var ID var
// 0 main_color 9 18 27 reserved (memcpy)
// 1 10 19 28 reserved (memcpy)
// 2 MEMCPYH2D_1 11 20 29 reserved
// 3 MEMCPYH2D_2 12 21 reserved (memcpy) 30 reserved (memcpy)
// 4 MEMCPYD2H_1 13 22 reserved (memcpy) 31 reserved
// 5 14 23 reserved (memcpy) 32
// 6 15 24 33
// 7 16 25 34
// 8 17 26 35
// See task maps in sentinel.csl and pe_program.csl
// +--------------+ +----------------+
// MEMCPYH2D_1 -> | sentinel.csl | -> main_color -> | pe_program.csl | -> MEMCPYD2H_1
// MEMCPYH2D_2 -> | | +----------------+
// +--------------+
// IDs for memcpy streaming colors
param MEMCPYH2D_DATA_1_ID: i16;
param MEMCPYH2D_DATA_2_ID: i16;
param MEMCPYD2H_DATA_1_ID: i16;
// number of PEs in a column
param size: i16;
// Sentinel to tell PE that it is time to send the result to the host
const end_computation: u16 = 43;
// Colors
const MEMCPYH2D_DATA_1: color = @get_color(MEMCPYH2D_DATA_1_ID);
const MEMCPYH2D_DATA_2: color = @get_color(MEMCPYH2D_DATA_2_ID);
const MEMCPYD2H_DATA_1: color = @get_color(MEMCPYD2H_DATA_1_ID);
const main_color: color = @get_color(0);
const memcpy = @import_module("<memcpy/get_params>", .{
.width = 2,
.height = size,
.MEMCPYH2D_1 = MEMCPYH2D_DATA_1,
.MEMCPYH2D_2 = MEMCPYH2D_DATA_2,
.MEMCPYD2H_1 = MEMCPYD2H_DATA_1
});
layout {
@set_rectangle(2, size);
for (@range(u16, size)) |idx| {
@set_tile_code(0, idx, "sentinel.csl", .{
.memcpy_params = memcpy.get_params(0),
.main_color = main_color,
.sentinel = end_computation,
});
@set_color_config(0, idx, main_color,.{ .routes = .{ .rx = .{ RAMP }, .tx = .{ EAST }}});
@set_tile_code(1, idx, "pe_program.csl", .{
.memcpy_params = memcpy.get_params(1),
.main_color = main_color,
.sentinel = end_computation,
});
@set_color_config(1, idx, main_color, .{ .routes = .{ .rx = .{ WEST }, .tx = .{ RAMP }}});
}
}
pe_program.csl¶
// WSE-2 task ID map
// On WSE-2, data tasks are bound to colors (IDs 0 through 24)
//
// ID var ID var ID var ID var
// 0 main_task_id 9 18 27 reserved (memcpy)
// 1 10 19 28 reserved (memcpy)
// 2 11 20 29 reserved
// 3 12 21 reserved (memcpy) 30 reserved (memcpy)
// 4 13 22 reserved (memcpy) 31 reserved
// 5 14 23 reserved (memcpy) 32
// 6 15 24 33
// 7 16 25 34
// 8 17 26 35
// ...
// 43 sentinel_task_id
// WSE-3 task ID map
// On WSE-3, data tasks are bound to input queues (IDs 0 through 7)
//
// ID var ID var ID var ID var
// 0 reserved (memcpy) 9 18 27 reserved (memcpy)
// 1 reserved (memcpy) 10 19 28 reserved (memcpy)
// 2 main_task_id 11 20 29 reserved
// 3 12 21 reserved (memcpy) 30 reserved (memcpy)
// 4 13 22 reserved (memcpy) 31 reserved
// 5 14 23 reserved (memcpy) 32
// 6 15 24 33
// 7 16 25 34
// 8 17 26 35
// ...
// 43 sentinel_task_id
param memcpy_params: comptime_struct;
const sys_mod = @import_module("<memcpy/memcpy>", memcpy_params);
// Sentinel to signal end of data
param sentinel: u16;
// Colors
param main_color: color;
// Queue IDs
const main_iq: input_queue = @get_input_queue(2);
const d2h_1_oq: output_queue = @get_output_queue(3);
// Task IDs
// On WSE-2, data task IDs are created from colors; on WSE-3, from input queues
const main_task_id: data_task_id =
if (@is_arch("wse2")) @get_data_task_id(main_color)
else if (@is_arch("wse3")) @get_data_task_id(main_iq);
const send_result_task_id: control_task_id = @get_control_task_id(sentinel);
// Accumulate all received values along main_color in result[0]
var result = @zeros([1]f32);
const result_dsd = @get_dsd(mem1d_dsd, .{ .tensor_access = |i|{1} -> result[i] });
const out_dsd = @get_dsd(fabout_dsd, .{
.fabric_color = sys_mod.MEMCPYD2H_1,
.extent = 1,
.output_queue = d2h_1_oq
});
task main_task(data: f32) void {
result[0] += data;
}
task send_result() void {
@fmovs(out_dsd, result_dsd, .{ .async = true });
}
comptime {
@bind_data_task(main_task, main_task_id);
@bind_control_task(send_result, send_result_task_id);
// On WSE-3, we must explicitly initialize input and output queues
if (@is_arch("wse3")) {
@initialize_queue(main_iq, .{ .color = main_color });
@initialize_queue(d2h_1_oq, .{ .color = sys_mod.MEMCPYD2H_1 });
}
}
run.py¶
#!/usr/bin/env cs_python
import argparse
import json
import numpy as np
from cerebras.sdk.runtime.sdkruntimepybind import SdkRuntime, MemcpyDataType # pylint: disable=no-name-in-module
from cerebras.sdk.runtime.sdkruntimepybind import MemcpyOrder # pylint: disable=no-name-in-module
parser = argparse.ArgumentParser()
parser.add_argument('--name', help='the test name')
parser.add_argument("--cmaddr", help="IP:port for CS system")
args = parser.parse_args()
dirname = args.name
# Parse the compile metadata
with open(f"{dirname}/out.json", encoding="utf-8") as json_file:
compile_data = json.load(json_file)
params = compile_data["params"]
MEMCPYH2D_DATA_1 = int(params["MEMCPYH2D_DATA_1_ID"])
MEMCPYH2D_DATA_2 = int(params["MEMCPYH2D_DATA_2_ID"])
MEMCPYD2H_DATA_1 = int(params["MEMCPYD2H_DATA_1_ID"])
size = int(params["size"])
print(f"MEMCPYH2D_DATA_1 = {MEMCPYH2D_DATA_1}")
print(f"MEMCPYH2D_DATA_2 = {MEMCPYH2D_DATA_2}")
print(f"MEMCPYD2H_DATA_1 = {MEMCPYD2H_DATA_1}")
print(f"size = {size}")
memcpy_dtype = MemcpyDataType.MEMCPY_32BIT
runner = SdkRuntime(dirname, cmaddr=args.cmaddr)
runner.load()
runner.run()
num_wvlts = 11
print(f"num_wvlts = number of wavelets for each PE = {num_wvlts}")
print("step 1: streaming H2D_1 sends number of input wavelets to P0")
h2d1_u32 = np.ones(size).astype(np.uint32) * num_wvlts
runner.memcpy_h2d(MEMCPYH2D_DATA_1, h2d1_u32.ravel(), 0, 0, 1, size, 1, \
streaming=True, data_type=memcpy_dtype, order=MemcpyOrder.ROW_MAJOR, nonblock=True)
# Use a deterministic seed so that CI results are predictable
np.random.seed(seed=7)
# Setup a {size}x11 input tensor that is reduced along the second dimension
input_tensor = np.random.rand(size, num_wvlts).astype(np.float32)
expected = np.sum(input_tensor, axis=1)
print("step 2: streaming H2D_2 to P0")
runner.memcpy_h2d(MEMCPYH2D_DATA_2, input_tensor.ravel(), 0, 0, 1, size, num_wvlts, \
streaming=True, data_type=memcpy_dtype, order=MemcpyOrder.ROW_MAJOR, nonblock=True)
print("step 3: streaming D2H at P1")
result_tensor = np.zeros(size, np.float32)
runner.memcpy_d2h(result_tensor, MEMCPYD2H_DATA_1, 1, 0, 1, size, 1, \
streaming=True, data_type=memcpy_dtype, order=MemcpyOrder.ROW_MAJOR, nonblock=False)
runner.stop()
# Ensure that the result matches our expectation
np.testing.assert_allclose(result_tensor, expected, atol=0.05, rtol=0)
print("SUCCESS!")
commands.sh¶
#!/usr/bin/env bash
set -e
cslc --arch=wse2 ./layout.csl --fabric-dims=11,12 \
--fabric-offsets=4,1 -o out \
--params=MEMCPYH2D_DATA_1_ID:2 \
--params=MEMCPYH2D_DATA_2_ID:3 \
--params=MEMCPYD2H_DATA_1_ID:4 \
--params=size:4 \
--memcpy --channels=1 --width-west-buf=0 --width-east-buf=0
cs_python run.py --name out