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kernels/tests/kernel/tensor/flash_attn.py
2024-09-01 18:17:05 -07:00

159 lines
4.7 KiB
Python

import sys
import numpy as np
def parse_mnk():
if len(sys.argv) != 4:
print(f"usage: {sys.argv[0]} dimM dimN dimK", file=sys.stderr)
sys.exit(1)
m = int(sys.argv[1])
n = int(sys.argv[2])
k = int(sys.argv[3])
return (m, n, k)
# Reorder array in a way that groups two adjacent elements along the column to
# be now adjacent along the row. This way, when the resulting fp16 array is
# read in column-major order with 32-bit granularity, the fp16 elements will be
# read in the same order as regular fp32 elements in column-major.
#
# For example:
# [[1 2]
# [3 4]
# [5 6]
# [7 8]]
# becomes
# [[1 3 2 4]
# [5 7 6 8]]
def pack_fp16_by_column(array):
rows = array.shape[0]
cols = array.shape[1]
T = array.transpose([1, 0])
T_packed = T.reshape([cols, -1, 2])
result = T_packed.transpose([1, 0, 2])
return result
# Do the same as pack_fp16_by_column, but for every two elements along the row.
def pack_fp16_by_row(array):
rows = array.shape[0]
cols = array.shape[1]
result = array.reshape([rows, -1, 2])
return result
if __name__ == "__main__":
seqlen, _, headdim = parse_mnk()
rand = True
if not rand:
A_array = np.arange(seqlen * headdim).reshape([seqlen, headdim])
B_array = np.arange(headdim * seqlen).reshape([headdim, seqlen])
C_array = np.arange(seqlen * seqlen).reshape([seqlen, headdim])
else:
np.random.seed(0)
A_array = np.random.rand(seqlen, headdim) - 0.5
B_array = np.random.rand(headdim, seqlen) - 0.5
C_array = np.random.rand(seqlen, headdim) - 0.5
# C_array = np.zeros([M, N])
fp16 = False
if fp16:
A_packed = pack_fp16_by_row(A_array)
AT_packed = A_packed.transpose([1, 0, 2])
AT_array = AT_packed.reshape([-1, seqlen * 2])
AT_array.astype('float16').tofile("input.a.col.bin")
# print('AT:')
# print(AT_array)
B_packed = pack_fp16_by_column(B_array)
B_array = B_packed.reshape([-1, headdim * 2])
B_array.astype('float16').tofile("input.b.row.bin")
# print('B:')
# print(B_array)
else:
A_array.astype('float32').tofile("input.a.row.bin")
AT_array = A_array.transpose([1, 0])
AT_array.astype('float32').tofile("input.a.col.bin")
B_array.astype('float32').tofile("input.b.bin")
C_array.astype('float32').tofile("input.c.bin")
# print('AT:')
# print(AT_array)
# print('B:')
# print(B_array)
assert((seqlen % 64) == 0)
Br = 64
Bc = Br
rowmax = np.zeros([Br])
rowsum = np.zeros([Br])
O = np.zeros([Br, headdim])
def exp2(x):
return (x**2) / 2.0 + x + 1.0
full_S = A_array @ B_array
full_S_T = full_S.transpose([1, 0])
full_S.astype('float32').tofile("full_S.bin")
col_to_save = 0
for col in range(0, seqlen, Bc):
print(f"tile iteration {col}~{col + Bc} ======================================")
# FIXME: only work with the first 64 rows of Q for now
Q_tile = A_array[0:64, :]
K_tile = B_array[:, col:col+Bc]
S = Q_tile @ K_tile
if col == col_to_save:
print('S_expected:')
print(S)
S.astype('float32').tofile("S_expected.bin")
# generate rowmax result in online softmax
rowmax_this = np.max(S, axis=1)
rowmax_prev = rowmax.copy()
rowmax = np.maximum(rowmax, rowmax_this)
if col == col_to_save:
rowmax.astype('float32').tofile("rowmax.bin")
# subtrace rowmax from each row by broadcasting
# (placeholder for exp)
x = S - rowmax[:, np.newaxis]
P = exp2(x)
# for i in range(3, 4):
# P += (x**i) / np.math.factorial(i)
# P = np.exp(exp)
# print('P error:')
# print(P / np.exp(x))
if col == col_to_save:
print('P_expected:')
print(P)
P.astype('float32').tofile("P_expected.bin")
rowsum_this = np.sum(P, axis=1)
x = rowmax_prev - rowmax_this
rowsum = exp2(x) * rowsum + rowsum_this
if col == col_to_save:
rowsum.astype('float32').tofile("rowsum.bin")
x = rowmax_prev - rowmax
O = O / (exp2(x)[:, np.newaxis])
if col == col_to_save:
print('O_before_PV:')
print(O)
O.astype('float32').tofile("O_before_PV.bin")
V = C_array[col:col+Bc, :]
if col == col_to_save:
V.astype('float32').tofile("V_expected.bin")
# O = P.transpose([1, 0]) @ V
O = O + P @ V
if col == col_to_save:
print('O_after_PV:')
print(O)
O.astype('float32').tofile("O_after_PV.bin")