Soft Thresholding CUDA implementation
I am wondering how should I implement a nice soft thresholding function kernel in CUDA? The soft thresholding function is like following:
-
The two solutions proposed in the comments above, set up for an elementwise processing, are the following:
__global__ void myKernel1(float* __restrict__ x, float lambda, const int N) { int tid = threadIdx.x + blockIdx.x * blockDim.x; if (tid < N) { float xa = fabs(x[tid]); x[tid] = (xa > lambda) ? x[tid] * ((xa - lambda) / xa) : 0; } }and
__global__ void myKernel2(float* __restrict__ x, float lambda, const int N) { int tid = threadIdx.x + blockIdx.x * blockDim.x; if (tid < N) { float xa = fabs(x[tid]); x[tid] = signbit(lambda-xa)*copysign(xa-lambda,x[tid]); } }The disassembled codes for the two solutions are reported below. As noticed also by @njuffa, the second one seems to be in principle less burdened than the first one due to the lacking
x/|x|division. However, as also noticed by @njuffa, this scenario will be likely memory bound rather than compute bound. However, perhaps this analysis gives indication that the second solution is preferrable when implemented as__device__functions for non-elementwise computationS.DISASSEMBLED CODE FOR THE FIRST SOLUTION
code for sm_21 Function : _Z9myKernel1Pffi .headerflags @"EF_CUDA_SM20 EF_CUDA_PTX_SM(EF_CUDA_SM20)" /*0000*/ MOV R1, c[0x1][0x100]; /* 0x2800440400005de4 */ /*0008*/ S2R R0, SR_CTAID.X; /* 0x2c00000094001c04 */ /*0010*/ S2R R3, SR_TID.X; /* 0x2c0000008400dc04 */ /*0018*/ IMAD R0, R0, c[0x0][0x8], R3; /* 0x2006400020001ca3 */ /*0020*/ ISETP.GE.AND P0, PT, R0, c[0x0][0x2c], PT; /* 0x1b0e4000b001dc23 */ /*0028*/ @P0 EXIT ; /* 0x80000000000001e7 */ /*0030*/ MOV32I R3, 0x4; /* 0x180000001000dde2 */ /*0038*/ SSY 0x90; /* 0x6000000140000007 */ /*0040*/ IMAD R16.CC, R0, R3, c[0x0][0x20]; /* 0x2007800080041ca3 */ /*0048*/ IMAD.HI.X R17, R0, R3, c[0x0][0x24]; /* 0x2086800090045ce3 */ /*0050*/ LD.E R2, [R16]; /* 0x8400000001009c85 */ /*0058*/ FSETP.GT.AND P0, PT, |R2|, c[0x0][0x28], PT; /* 0x220e4000a021dc80 */ /*0060*/ F2F.F32.F32 R5, |R2|; /* 0x1000000009215c44 */ /*0068*/ @P0 BRA 0x78; /* 0x40000000200001e7 */ /*0070*/ MOV.S R0, RZ; /* 0x28000000fc001df4 */ /*0078*/ FADD R4, |R2|, -c[0x0][0x28]; /* 0x50004000a0211d80 */ /*0080*/ JCAL 0x0; /* 0x1000000000010007 */ /*0088*/ FMUL.S R0, R2, R4; /* 0x5800000010201c10 */ /*0090*/ ST.E [R16], R0; /* 0x9400000001001c85 */ /*0098*/ EXIT ; /* 0x8000000000001de7 */ ................................. Function : __cuda_sm20_div_rn_noftz_f32_slowpath .headerflags @"EF_CUDA_SM20 EF_CUDA_PTX_SM(EF_CUDA_SM20)" /*0000*/ SHL R0, R4, 0x1; /* 0x6000c00004401c03 */ /*0008*/ MOV32I R6, 0x1; /* 0x1800000004019de2 */ /*0010*/ SHL R3, R5, 0x1; /* 0x6000c0000450dc03 */ /*0018*/ IMAD.U32.U32.HI R0, R0, 0x100, -R6; /* 0x200cc00400001d43 */ /*0020*/ ISETP.GT.U32.AND P0, PT, R0, 0xfd, PT; /* 0x1a0ec003f401dc03 */ /*0028*/ IMAD.U32.U32.HI R3, R3, 0x100, -R6; /* 0x200cc0040030dd43 */ /*0030*/ ISETP.GT.U32.OR P0, PT, R3, 0xfd, P0; /* 0x1a20c003f431dc03 */ /*0038*/ @!P0 BRA 0x178; /* 0x40000004e00021e7 */ /*0040*/ FSETP.LE.AND P0, PT, |R4|, +INF , PT; /* 0x218edfe00041dc80 */ /*0048*/ @!P0 BRA 0x60; /* 0x40000000400021e7 */ /*0050*/ FSETP.LE.AND P0, PT, |R5|, +INF , PT; /* 0x218edfe00051dc80 */ /*0058*/ @P0 BRA 0x70; /* 0x40000000400001e7 */ /*0060*/ FADD R4, R4, R5; /* 0x5000000014411c00 */ /*0068*/ BRA 0x370; /* 0x4000000c00001de7 */ /*0070*/ SHL R7, R5, 0x1; /* 0x6000c0000451dc03 */ /*0078*/ SHL R6, R4, 0x1; /* 0x6000c00004419c03 */ /*0080*/ ISETP.EQ.U32.AND P2, PT, R7, RZ, PT; /* 0x190e0000fc75dc03 */ /*0088*/ ISETP.EQ.U32.AND P1, PT, R6, RZ, PT; /* 0x190e0000fc63dc03 */ /*0090*/ PSETP.AND.AND P0, PT, P1, P2, PT; /* 0x0c0e00000811dc04 */ /*0098*/ @P0 BRA 0xc0; /* 0x40000000800001e7 */ /*00a0*/ FSETP.EQ.AND P3, PT, |R4|, +INF , PT; /* 0x210edfe00047dc80 */ /*00a8*/ FSETP.EQ.AND P0, PT, |R5|, +INF , PT; /* 0x210edfe00051dc80 */ /*00b0*/ @!P3 BRA 0xd8; /* 0x4000000080002de7 */ /*00b8*/ @!P0 BRA 0xd8; /* 0x40000000600021e7 */ /*00c0*/ MOV32I R0, 0xffc00000; /* 0x1bff000000001de2 */ /*00c8*/ MUFU.RSQ R4, R0; /* 0xc800000014011c00 */ /*00d0*/ BRA 0x370; /* 0x4000000a60001de7 */ /*00d8*/ PSETP.OR.AND P0, PT, P0, P1, PT; /* 0x0c0e00004401dc04 */ /*00e0*/ @!P0 BRA 0x100; /* 0x40000000600021e7 */ /*00e8*/ LOP.XOR R0, R5, R4; /* 0x6800000010501c83 */ /*00f0*/ LOP32I.AND R4, R0, 0x80000000; /* 0x3a00000000011c02 */ /*00f8*/ BRA 0x370; /* 0x40000009c0001de7 */ /*0100*/ PSETP.OR.AND P0, PT, P3, P2, PT; /* 0x0c0e00004831dc04 */ /*0108*/ @!P0 BRA 0x130; /* 0x40000000800021e7 */ /*0110*/ LOP.XOR R0, R5, R4; /* 0x6800000010501c83 */ /*0118*/ LOP32I.AND R0, R0, 0x80000000; /* 0x3a00000000001c02 */ /*0120*/ LOP32I.OR R4, R0, 0x7f800000; /* 0x39fe000000011c42 */ /*0128*/ BRA 0x370; /* 0x4000000900001de7 */ /*0130*/ ISETP.GE.AND P1, PT, R0, RZ, PT; /* 0x1b0e0000fc03dc23 */ /*0138*/ ISETP.GE.AND P0, PT, R3, RZ, PT; /* 0x1b0e0000fc31dc23 */ /*0140*/ @!P1 MOV32I R6, 0xffffffc0; /* 0x1bffffff0001a5e2 */ /*0148*/ @!P1 FFMA R4, R4, 1.84467440737095520000e+019, RZ; /* 0x307ed7e000412400 */ /*0150*/ @P1 MOV R6, RZ; /* 0x28000000fc0185e4 */ /*0158*/ @P0 BRA 0x180; /* 0x40000000800001e7 */ /*0160*/ FFMA R5, R5, 1.84467440737095520000e+019, RZ; /* 0x307ed7e000515c00 */ /*0168*/ IADD R6, R6, 0x40; /* 0x4800c00100619c03 */ /*0170*/ BRA 0x180; /* 0x4000000020001de7 */ /*0178*/ MOV R6, RZ; /* 0x28000000fc019de4 */ /*0180*/ IADD R7, R3, -0x7e; /* 0x4800fffe0831dc03 */ /*0188*/ MOV32I R9, 0x3f800000; /* 0x18fe000000025de2 */ /*0190*/ ISCADD R7, -R7, R5, 0x17; /* 0x410000001471dee3 */ /*0198*/ ISUB R3, R0, R3; /* 0x480000000c00dd03 */ /*01a0*/ MUFU.RCP R8, R7; /* 0xc800000010721c00 */ /*01a8*/ IADD R5, R0, -0x7e; /* 0x4800fffe08015c03 */ /*01b0*/ FFMA R9, -R7, R8, R9; /* 0x3012000020725e00 */ /*01b8*/ ISCADD R4, -R5, R4, 0x17; /* 0x4100000010511ee3 */ /*01c0*/ FFMA R5, R8, R9, R8; /* 0x3010000024815c00 */ /*01c8*/ FFMA R8, R4, R5, RZ; /* 0x307e000014421c00 */ /*01d0*/ FFMA R9, -R7, R8, R4; /* 0x3008000020725e00 */ /*01d8*/ FFMA R8, R9, R5, R8; /* 0x3010000014921c00 */ /*01e0*/ FFMA R7, -R7, R8, R4; /* 0x300800002071de00 */ /*01e8*/ FFMA R4, R7, R5, R8; /* 0x3010000014711c00 */ /*01f0*/ SHL R9, R4, 0x1; /* 0x6000c00004425c03 */ /*01f8*/ SHR.U32 R9, R9, 0x18; /* 0x5800c00060925c03 */ /*0200*/ IADD R0, R3, R9; /* 0x4800000024301c03 */ /*0208*/ IADD R6, R6, R0; /* 0x4800000000619c03 */ /*0210*/ IADD R0, R6, -0x1; /* 0x4800fffffc601c03 */ /*0218*/ ISETP.GT.U32.AND P0, PT, R0, 0xfd, PT; /* 0x1a0ec003f401dc03 */ /*0220*/ @P0 BRA 0x240; /* 0x40000000600001e7 */ /*0228*/ ISUB R0, R6, R9; /* 0x4800000024601d03 */ /*0230*/ ISCADD R4, R0, R4, 0x17; /* 0x4000000010011ee3 */ /*0238*/ BRA 0x370; /* 0x40000004c0001de7 */ /*0240*/ ISETP.LE.AND P0, PT, R6, 0xfe, PT; /* 0x198ec003f861dc23 */ /*0248*/ @P0 BRA 0x268; /* 0x40000000600001e7 */ /*0250*/ LOP32I.AND R0, R4, 0x80000000; /* 0x3a00000000401c02 */ /*0258*/ LOP32I.OR R4, R0, 0x7f800000; /* 0x39fe000000011c42 */ /*0260*/ BRA 0x370; /* 0x4000000420001de7 */ /*0268*/ ISETP.GT.AND P0, PT, R6, RZ, PT; /* 0x1a0e0000fc61dc23 */ /*0270*/ @P0 BRA 0x370; /* 0x40000003e00001e7 */ /*0278*/ ISETP.GE.AND P0, PT, R6, -0x18, PT; /* 0x1b0effffa061dc23 */ /*0280*/ @P0 BRA 0x298; /* 0x40000000400001e7 */ /*0288*/ LOP32I.AND R4, R4, 0x80000000; /* 0x3a00000000411c02 */ /*0290*/ BRA 0x370; /* 0x4000000360001de7 */ /*0298*/ FFMA.RP R3, R7, R5, R8; /* 0x311000001470dc00 */ /*02a0*/ FFMA.RM R0, R7, R5, R8; /* 0x3090000014701c00 */ /*02a8*/ FFMA.RZ R5, R7, R5, R8; /* 0x3190000014715c00 */ /*02b0*/ FSET.NEU.AND R3, R0, R3, PT; /* 0x168e00000c00dc00 */ /*02b8*/ I2I.S32.S32 R7, -R6; /* 0x1c0000001921df84 */ /*02c0*/ LOP32I.AND R5, R5, 0x7fffff; /* 0x3801fffffc515c02 */ /*02c8*/ ISETP.EQ.AND P0, PT, R7, RZ, PT; /* 0x190e0000fc71dc23 */ /*02d0*/ LOP32I.AND R0, R4, 0x80000000; /* 0x3a00000000401c02 */ /*02d8*/ I2I.S32.S32 R3, -R3; /* 0x1c0000000d20df84 */ /*02e0*/ I2I.S32.S32 R4, -R6; /* 0x1c00000019211f84 */ /*02e8*/ LOP32I.OR R7, R5, 0x800000; /* 0x380200000051dc42 */ /*02f0*/ @P0 BRA.U 0x328; /* 0x40000000c00081e7 */ /*02f8*/ @!P0 IADD R5, R6, 0x20; /* 0x4800c00080616003 */ /*0300*/ @!P0 SHL R5, R7, R5; /* 0x6000000014716003 */ /*0308*/ @!P0 ICMP.EQ.U32 R5, RZ, 0x1, R5; /* 0x310ac00007f16003 */ /*0310*/ @!P0 SHR.U32 R7, R7, R4; /* 0x580000001071e003 */ /*0318*/ @!P0 LOP.OR R3, R3, R5; /* 0x680000001430e043 */ /*0320*/ NOP; /* 0x4000000000001de4 */ /*0328*/ SHL R4, R7, 0x1e; /* 0x6000c00078711c03 */ /*0330*/ SHR.U32 R5, R4, 0x1f; /* 0x5800c0007c415c03 */ /*0338*/ LOP.AND R4, R7, 0x1; /* 0x6800c00004711c03 */ /*0340*/ LOP.OR R3, R3, R5; /* 0x680000001430dc43 */ /*0348*/ LOP.AND R3, R4, R3; /* 0x680000000c40dc03 */ /*0350*/ SHR.U32 R4, R7, 0x1; /* 0x5800c00004711c03 */ /*0358*/ ISETP.NE.U32.AND P0, PT, R3, RZ, PT; /* 0x1a8e0000fc31dc03 */ /*0360*/ @P0 IADD R4, R4, 0x1; /* 0x4800c00004410003 */ /*0368*/ LOP.OR R4, R0, R4; /* 0x6800000010011c43 */ /*0370*/ RET ; /* 0x9000000000001de7 */ ...................................................... Function : __cuda_sm20_div_rn_f32 .headerflags @"EF_CUDA_SM20 EF_CUDA_PTX_SM(EF_CUDA_SM20)" /*0000*/ MUFU.RCP R3, R5; /* 0xc80000001050dc00 */ /*0008*/ MOV32I R6, 0x3f800000; /* 0x18fe000000019de2 */ /*0010*/ LOP32I.AND R0, R4, 0x7fffff; /* 0x3801fffffc401c02 */ /*0018*/ FFMA.FTZ R6, -R5, R3, R6; /* 0x300c00000c519e40 */ /*0020*/ LOP32I.OR R0, R0, 0x3f800000; /* 0x38fe000000001c42 */ /*0028*/ FFMA.FTZ R3, R3, R6, R3; /* 0x300600001830dc40 */ /*0030*/ FFMA.FTZ R6, R0, R3, RZ; /* 0x307e00000c019c40 */ /*0038*/ FFMA.FTZ R7, -R5, R6, R0; /* 0x300000001851de40 */ /*0040*/ FFMA.FTZ R6, R7, R3, R6; /* 0x300c00000c719c40 */ /*0048*/ FFMA.FTZ R0, -R5, R6, R0; /* 0x3000000018501e40 */ /*0050*/ LOP32I.AND R7, R4, 0xff800000; /* 0x3bfe00000041dc02 */ /*0058*/ FFMA.FTZ R6, R0, R3, R6; /* 0x300c00000c019c40 */ /*0060*/ FFMA.FTZ R0, R6, R7, RZ; /* 0x307e00001c601c40 */ /*0068*/ LOP32I.AND R3, R0, 0x7fffffff; /* 0x39fffffffc00dc02 */ /*0070*/ MOV32I R6, 0x7effffef; /* 0x19fbffffbc019de2 */ /*0078*/ IADD32I R3, R3, -0x800010; /* 0x0bfdffffc030dc02 */ /*0080*/ ISETP.GT.U32.AND P0, PT, R3, R6, PT; /* 0x1a0e00001831dc03 */ /*0088*/ @!P0 BRA 0xa8; /* 0x40000000600021e7 */ /*0090*/ JCAL 0x0; /* 0x1000000000010007 */ /*0098*/ MOV R0, R4; /* 0x2800000010001de4 */ /*00a0*/ NOP; /* 0x4000000000001de4 */ /*00a8*/ MOV R4, R0; /* 0x2800000000011de4 */ /*00b0*/ RET ; /* 0x9000000000001de7 */ .......................................DISASSEMBLED CODE FOR THE SECOND SOLUTION
code for sm_21 Function : _Z9myKernel2Pffi .headerflags @"EF_CUDA_SM20 EF_CUDA_PTX_SM(EF_CUDA_SM20)" /*0000*/ MOV R1, c[0x1][0x100]; /* 0x2800440400005de4 */ /*0008*/ S2R R0, SR_CTAID.X; /* 0x2c00000094001c04 */ /*0010*/ S2R R2, SR_TID.X; /* 0x2c00000084009c04 */ /*0018*/ IMAD R0, R0, c[0x0][0x8], R2; /* 0x2004400020001ca3 */ /*0020*/ ISETP.GE.AND P0, PT, R0, c[0x0][0x2c], PT; /* 0x1b0e4000b001dc23 */ /*0028*/ @P0 BRA.U 0x98; /* 0x40000001a00081e7 */ /*0030*/ @!P0 MOV32I R3, 0x4; /* 0x180000001000e1e2 */ /*0038*/ @!P0 IMAD R2.CC, R0, R3, c[0x0][0x20]; /* 0x200780008000a0a3 */ /*0040*/ @!P0 IMAD.HI.X R3, R0, R3, c[0x0][0x24]; /* 0x208680009000e0e3 */ /*0048*/ @!P0 LD.E R0, [R2]; /* 0x8400000000202085 */ /*0050*/ @!P0 FADD R5, |R0|, -c[0x0][0x28]; /* 0x50004000a0016180 */ /*0058*/ @!P0 FADD R4, -|R0|, c[0x0][0x28]; /* 0x50004000a0012280 */ /*0060*/ @!P0 LOP32I.AND R0, R0, 0x80000000; /* 0x3a00000000002002 */ /*0068*/ @!P0 LOP32I.AND R5, R5, 0x7fffffff; /* 0x39fffffffc516002 */ /*0070*/ @!P0 SHR.U32 R4, R4, 0x1f; /* 0x5800c0007c412003 */ /*0078*/ @!P0 LOP.OR R5, R0, R5; /* 0x6800000014016043 */ /*0080*/ @!P0 I2F.F32.S32 R0, R4; /* 0x1800000011202204 */ /*0088*/ @!P0 FMUL R0, R0, R5; /* 0x5800000014002000 */ /*0090*/ @!P0 ST.E [R2], R0; /* 0x9400000000202085 */ /*0098*/ EXIT ; /* 0x8000000000001de7 */ .................................EDIT
A follow-up of this post has appeared in Soft thresholding in CUDA.
讨论(0)
加载中...
- 热议问题