"WebGL 2 compute" NxN matrix multiplication C = A x B (SGEMM) v.4_4 demo.
See Kernel 4:
Wider data-types by Cedric Nugteren.
All A, B elements are random (0 - 1). Error "er1" is calculated as
the sum of |CCPU - CGPU |/(N*N) for all matrix elements.
er2 = max(|CCPU - CGPU |).
See also Shader 4_8 benchmark.
#version 310 es
#define TS 32u
#define WIDTH 8u
#define TSW 4u // TS/WIDTH
layout (local_size_x = TSW, local_size_y = TS, local_size_z = 1) in;
layout (std430, binding = 0) readonly buffer ssbA {
mat2x4 A[];
};
layout (std430, binding = 1) readonly buffer ssbB {
mat2x4 B[];
};
layout (std430, binding = 2) writeonly buffer ssbC {
mat2x4 C[];
};
uniform uvec3 MNK;
shared mat2x4 Asub[TS][TS/WIDTH]; // Local memory to fit a tile of
shared mat2x4 Bsub[TS][TS/WIDTH]; // TS*TS elements of A and B
void main() {
uint M = MNK.x, N = MNK.y, K = MNK.z;
// Thread identifiers
uint row = gl_LocalInvocationID.x; // Local row ID (max: TS/WIDTH)
uint col = gl_LocalInvocationID.y; // Local col ID (max: TS)
uint globalRow = (TS/WIDTH)*gl_WorkGroupID.x + row; // Row ID of C (0..M/WIDTH)
uint globalCol = TS*gl_WorkGroupID.y + col; // Col ID of C (0..N)
// Initialise the accumulation register
mat2x4 acc = mat2x4(vec4(0.0),vec4(0.0));
// Loop over all tiles
uint numTiles = K/TS;
for (uint t=0u; t < numTiles; t++) {
// Load one tile of A and B into local memory
uint tiledRow = (TS/WIDTH)*t + row;
uint tiledCol = TS*t + col;
Asub[col][row] = A[tiledCol*(M/WIDTH) + globalRow];
Bsub[col][row] = B[globalCol*(K/WIDTH) + tiledRow];
// Synchronise to make sure the tile is loaded
memoryBarrierShared();
barrier();
// Perform the computation for a single tile
mat2x4 vecB;
for (uint k=0u; k < TS/WIDTH; k++) {
vecB = Bsub[col][k];
acc += Asub[WIDTH*k][row] * vecB[0][0];
acc += Asub[WIDTH*k + 1u][row] * vecB[0][1];
acc += Asub[WIDTH*k + 2u][row] * vecB[0][2];
acc += Asub[WIDTH*k + 3u][row] * vecB[0][3];
acc += Asub[WIDTH*k + 4u][row] * vecB[1][0];
acc += Asub[WIDTH*k + 5u][row] * vecB[1][1];
acc += Asub[WIDTH*k + 6u][row] * vecB[1][2];
acc += Asub[WIDTH*k + 7u][row] * vecB[1][3];
}
// Synchronise before loading the next tile
barrier();
}
// Store the final result in C
C[globalCol*(M/WIDTH) + globalRow] = acc;
}
What is optimal data (GPU regiser) length for mobile GPU?