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// Compute tensor = GELU( tensor + repeat( pattern, tensor ) ) in 1 shot, without VRAM allocations
// Dispatch [ nb[ 1 ], nb[ 2 ], nb[ 3 ] ] thread groups of this shader, where nb is size of the destination tensor
RWBuffer<float> tensor: register( u0 );
Buffer<float> pattern: register( t0 );
Buffer<uint> lookupTable: register( t1 );
cbuffer Constants: register( b0 )
{
uint4 tensorSize: packoffset( c0 );
uint4 tensorStrides: packoffset( c1 );
uint4 patternSize: packoffset( c2 );
uint4 patternStrides: packoffset( c3 );
}
#ifndef THREADS
#define THREADS 1024
#endif
#include "repeatUtils.hlsli"
#include "miscUtils.hlsli"
inline float gelu( float x )
{
#if 1
const uint index = fp16Rounded( x );
const uint res16 = lookupTable[ index ];
return f16tof32( res16 );
#else
// This version is much slower, at least on AMD, despite saving these VRAM loads.
const float GELU_COEF_A = 0.044715;
const float SQRT_2_OVER_PI = 0.79788456080286535587989211986876;
return 0.5 * x * ( 1.0 + tanh( SQRT_2_OVER_PI * x * ( 1.0 + GELU_COEF_A * x * x ) ) );
#endif
}
inline void computeSimple( uint idx, float add )
{
float f = tensor[ idx ];
f += add;
f = gelu( f );
tensor[ idx ] = f;
}
[ numthreads( THREADS, 1, 1 ) ]
void main( uint3 group: SV_GroupID, uint thread : SV_GroupIndex )
{
uint3 it = tensorIteratorState( group, thread, tensorSize, tensorStrides );
uint rsi = rowOffset( group % patternSize.yzw, patternStrides );
if( patternSize[ 0 ] == 1 )
{
// The pattern only has 1 column - broadcasting over the row
const float p = pattern[ rsi ];
ROW_LOOP( it )
computeSimple( it.x, p );
}
else if( patternSize[ 0 ] <= THREADS )
{
// pattern size doesn't exceed thread group size: load pattern value outside of the loop
const uint threadsPerGroup = THREADS - ( THREADS % patternSize[ 0 ] );
if( thread >= threadsPerGroup )
return;
const float p = pattern[ rsi + ( thread % patternSize[ 0 ] ) * patternStrides[ 0 ] ];
ROW_LOOP_EX( it, threadsPerGroup, tensorStrides )
computeSimple( it.x, p );
}
else
{
// Pattern rows are larger than the thread group, need to stream from both buffers
const uint rsiInc = THREADS * patternStrides[ 0 ];
const uint rsiDec = patternSize[ 0 ] * patternStrides[ 0 ];
const uint rsiEnd = rsi + rsiDec;
rsi += thread * patternStrides[ 0 ];
ROW_LOOP( it )
{
float f = tensor[ it.x ];
float p = pattern[ rsi ];
rsi += rsiInc;
if( rsi >= rsiEnd )
rsi -= rsiDec;
f += p;
f = gelu( f );
tensor[ it.x ] = f;
}
}
}
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