| // Copyright 2019 Google LLC |
| // |
| // This source code is licensed under the BSD-style license found in the |
| // LICENSE file in the root directory of this source tree. |
| |
| $assert BATCH_TILE % 4 == 0 |
| $assert BATCH_TILE >= 4 |
| $ABC = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ" |
| #include <assert.h> |
| |
| #include <psimd.h> |
| |
| #include <xnnpack/common.h> |
| #include <xnnpack/vunary.h> |
| |
| |
| void xnn_f32_sigmoid_ukernel__psimd_p5_div_x${BATCH_TILE}( |
| size_t n, |
| const float* x, |
| float* y, |
| const void* params) |
| { |
| assert(n % sizeof(float) == 0); |
| |
| const psimd_f32 vmagic_bias = psimd_splat_f32(0x1.8000FEp23f); |
| // The largest z for which sigmoidf(-z) is normalized. |
| // This number is also the largest z for which expf(-z) is normalized. |
| const psimd_f32 vdenorm_cutoff = psimd_splat_f32(0x1.5D589Ep+6f); |
| const psimd_f32 vminus_log2e = psimd_splat_f32(-0x1.715476p+0f); |
| // Last 7 bits are zeroes |
| const psimd_f32 vln2_hi = psimd_splat_f32(0x1.62E400p-1f); |
| const psimd_f32 vln2_lo = psimd_splat_f32(0x1.7F7D1Cp-20f); |
| const psimd_f32 vone = psimd_splat_f32(1.0f); |
| |
| const psimd_f32 vc1 = psimd_splat_f32(-0x1.FFFFF6p-1f); |
| const psimd_f32 vc2 = psimd_splat_f32( 0x1.FFFDC6p-2f); |
| const psimd_f32 vc3 = psimd_splat_f32(-0x1.555A80p-3f); |
| const psimd_f32 vc4 = psimd_splat_f32( 0x1.573A1Ap-5f); |
| const psimd_f32 vc5 = psimd_splat_f32(-0x1.0F9F9Cp-7f); |
| |
| $if BATCH_TILE > 4: |
| for (; n >= ${BATCH_TILE} * sizeof(float); n -= ${BATCH_TILE} * sizeof(float)) { |
| const psimd_f32 vx${ABC[0:4]} = psimd_load_f32(x); |
| $for N in range(4, BATCH_TILE, 4): |
| const psimd_f32 vx${ABC[N:N+4]} = psimd_load_f32(x + ${N}); |
| x += ${BATCH_TILE}; |
| |
| // General structure of the algorithm: |
| // / exp(x) / (1 + exp(x)) if x <= 0 |
| // f[x] := |
| // \ 1 - f[-x] if x >= 0 |
| // |
| // First we compute f[-z] := exp(-z) / (1 + exp(-z)) where z = abs(x), |
| // then replace result with 1 - f[-z] if x >= 0. |
| $for N in range(0, BATCH_TILE, 4): |
| const psimd_f32 vz${ABC[N:N+4]} = psimd_abs_f32(vx${ABC[N:N+4]}); |
| |
| // Compute reduced argument n := round(-z / log(2)). |
| // We do it by adding a large number (magic bias), which cause rounding of result to an integer, then subtracing the |
| // large number back. The first addition is combined with multiplication by log2e into a single FMA instruction. |
| // The trick with adding large number is valid only within certain bounds (|x| <= 2**22), but thats ok, because |
| // inputs x outside of [-87.336544, 17.328678] (i.e. z outsize [0, 87.336544]) underflow or saturate sigmoidf(x) |
| // anyway. We fixup the result for such inputs at the very end of the algorithm. |
| $for N in range(0, BATCH_TILE, 4): |
| psimd_f32 vn${ABC[N:N+4]} = psimd_qfma_f32(vmagic_bias, vz${ABC[N:N+4]}, vminus_log2e); |
| |
| // Create a floating-point number s (scale) such that s == 2**n for inputs which don't cause underflow, i.e. |
| // -87.336544 <= -z <= 0.0, and -126 <= n <= 0 accordingly. |
| $for N in range(0, BATCH_TILE, 4): |
| const psimd_f32 vs${ABC[N:N+4]} = (psimd_f32) ((psimd_u32) vn${ABC[N:N+4]} << 23); |
| |
| // Subtract the large number back to get the final n := round(-z / log(2)) as a floating-point number. |
| $for N in range(0, BATCH_TILE, 4): |
| vn${ABC[N:N+4]} = psimd_sub_f32(vn${ABC[N:N+4]}, vmagic_bias); |
| |
| // Compute reduced argument t := z + n * log(2). Note that -t = -z - n * log(2). |
| // Use Cody-Waite range reduction method (note two constants to represent log(2)) to improve accuracy. |
| $for N in range(0, BATCH_TILE, 4): |
| psimd_f32 vt${ABC[N:N+4]} = psimd_qfma_f32(vz${ABC[N:N+4]}, vn${ABC[N:N+4]}, vln2_hi); |
| |
| $for N in range(0, BATCH_TILE, 4): |
| vt${ABC[N:N+4]} = psimd_qfma_f32(vt${ABC[N:N+4]}, vn${ABC[N:N+4]}, vln2_lo); |
| |
| // Compute degree-5 polynomial approximation for exp(-t) on [-log(2)/2, log(2)/2]: |
| // P5(t) = 1 + t * (c1 + t * (c2 + t * (c3 + t * (c4 + t * c5)))) |
| $for N in range(0, BATCH_TILE, 4): |
| psimd_f32 vp${ABC[N:N+4]} = psimd_qfma_f32(vc4, vt${ABC[N:N+4]}, vc5); |
| |
| $for N in range(0, BATCH_TILE, 4): |
| vp${ABC[N:N+4]} = psimd_qfma_f32(vc3, vt${ABC[N:N+4]}, vp${ABC[N:N+4]}); |
| |
| $for N in range(0, BATCH_TILE, 4): |
| vp${ABC[N:N+4]} = psimd_qfma_f32(vc2, vt${ABC[N:N+4]}, vp${ABC[N:N+4]}); |
| |
| $for N in range(0, BATCH_TILE, 4): |
| vp${ABC[N:N+4]} = psimd_qfma_f32(vc1, vt${ABC[N:N+4]}, vp${ABC[N:N+4]}); |
| |
| // Reconstruct the exp(-z) value: |
| // e = s * (1 + t * (c1 + t * (c2 + t * (c3 + t * (c4 + t * c5))))) |
| // = s + (t * s) * (c1 + t * (c2 + t * (c3 + t * (c4 + t * c5)))) |
| // = s + (t * s) * p |
| $for N in range(0, BATCH_TILE, 4): |
| vt${ABC[N:N+4]} = psimd_mul_f32(vt${ABC[N:N+4]}, vs${ABC[N:N+4]}); |
| |
| $for N in range(0, BATCH_TILE, 4): |
| const psimd_f32 ve${ABC[N:N+4]} = psimd_qfma_f32(vs${ABC[N:N+4]}, vt${ABC[N:N+4]}, vp${ABC[N:N+4]}); |
| |
| // Reconstruct sigmoid(-z) = exp(-z) / (1.0 + exp(-z)) |
| $for N in range(0, BATCH_TILE, 4): |
| psimd_f32 vf${ABC[N:N+4]} = psimd_div_f32(ve${ABC[N:N+4]}, psimd_add_f32(ve${ABC[N:N+4]}, vone)); |
| |
| // For inputs above denormal cutoff, replace output with +0.0f. |
| // Note that for NaN inputs, comparison result is false, and outputs are left unchanged. |
| $for N in range(0, BATCH_TILE, 4): |
| vf${ABC[N:N+4]} = psimd_andnotmask_f32(vz${ABC[N:N+4]} > vdenorm_cutoff, vf${ABC[N:N+4]}); |
| |
| // Reconstruct sigmoid(x) = x < 0 ? sigmoid(-z) : 1.0 - sigmoid(-z) |
| $for N in range(0, BATCH_TILE, 4): |
| vf${ABC[N:N+4]} = psimd_signblend_f32(vx${ABC[N:N+4]}, vf${ABC[N:N+4]}, psimd_sub_f32(vone, vf${ABC[N:N+4]})); |
| |
| psimd_store_f32(y, vf${ABC[0:4]}); |
| $for N in range(4, BATCH_TILE, 4): |
| psimd_store_f32(y + ${N}, vf${ABC[N:N+4]}); |
| y += ${BATCH_TILE}; |
| } |
| for (; n >= 4 * sizeof(float); n -= 4 * sizeof(float)) { |
| const psimd_f32 vx = psimd_load_f32(x); |
| x += 4; |
| |
| // General structure of the algorithm: |
| // / exp(x) / (1 + exp(x)) if x <= 0 |
| // f[x] := |
| // \ 1 - f[-x] if x >= 0 |
| // |
| // First we compute f[-z] := exp(-z) / (1 + exp(-z)) where z = abs(x), |
| // then replace result with 1 - f[-z] if x >= 0. |
| const psimd_f32 vz = psimd_abs_f32(vx); |
| |
| // Compute reduced argument n := round(-z / log(2)). |
| // We do it by adding a large number (magic bias), which cause rounding of result to an integer, then subtracing the |
| // large number back. The first addition is combined with multiplication by log2e into a single FMA instruction. |
| // The trick with adding large number is valid only within certain bounds (|x| <= 2**22), but thats ok, because |
| // inputs x outside of [-87.336544, 17.328678] (i.e. z outsize [0, 87.336544]) underflow or saturate sigmoidf(x) |
| // anyway. We fixup the result for such inputs at the very end of the algorithm. |
| psimd_f32 vn = psimd_qfma_f32(vmagic_bias, vz, vminus_log2e); |
| |
| // Create a floating-point number s (scale) such that s == 2**n for inputs which don't cause underflow, i.e. |
| // -87.336544 <= -z <= 0.0, and -126 <= n <= 0 accordingly. |
| const psimd_f32 vs = (psimd_f32) ((psimd_u32) vn << 23); |
| |
| // Subtract the large number back to get the final n := round(-z / log(2)) as a floating-point number. |
| vn = psimd_sub_f32(vn, vmagic_bias); |
| |
| // Compute reduced argument t := z + n * log(2). Note that -t = -z - n * log(2). |
| // Use Cody-Waite range reduction method (note two constants to represent log(2)) to improve accuracy. |
| psimd_f32 vt = psimd_qfma_f32(vz, vn, vln2_hi); |
| vt = psimd_qfma_f32(vt, vn, vln2_lo); |
| |
| // Compute degree-5 polynomial approximation for exp(-t) on [-log(2)/2, log(2)/2]: |
| // P5(t) = 1 + t * (c1 + t * (c2 + t * (c3 + t * (c4 + t * c5)))) |
| psimd_f32 vp = psimd_qfma_f32(vc4, vt, vc5); |
| vp = psimd_qfma_f32(vc3, vt, vp); |
| vp = psimd_qfma_f32(vc2, vt, vp); |
| vp = psimd_qfma_f32(vc1, vt, vp); |
| |
| // Reconstruct the exp(-z) value: |
| // e = s * (1 + t * (c1 + t * (c2 + t * (c3 + t * (c4 + t * c5))))) |
| // = s + (t * s) * (c1 + t * (c2 + t * (c3 + t * (c4 + t * c5)))) |
| // = s + (t * s) * p |
| vt = psimd_mul_f32(vt, vs); |
| const psimd_f32 ve = psimd_qfma_f32(vs, vt, vp); |
| |
| // Reconstruct sigmoid(-z) = exp(-z) / (1.0 + exp(-z)) |
| psimd_f32 vf = psimd_div_f32(ve, psimd_add_f32(ve, vone)); |
| |
| // For inputs above denormal cutoff, replace output with +0.0f. |
| // Note that for NaN inputs, comparison result is false, and outputs are left unchanged. |
| vf = psimd_andnotmask_f32(vz > vdenorm_cutoff, vf); |
| |
| // Reconstruct sigmoid(x) = x < 0 ? sigmoid(-z) : 1.0 - sigmoid(-z) |
| vf = psimd_signblend_f32(vx, vf, psimd_sub_f32(vone, vf)); |
| |
| psimd_store_f32(y, vf); |
| y += 4; |
| } |
| if XNN_UNLIKELY(n != 0) { |
| const psimd_f32 vx = psimd_load_f32(x); |
| |
| // General structure of the algorithm: |
| // / exp(x) / (1 + exp(x)) if x <= 0 |
| // f[x] := |
| // \ 1 - f[-x] if x >= 0 |
| // |
| // First we compute f[-z] := exp(-z) / (1 + exp(-z)) where z = abs(x), |
| // then replace result with 1 - f[-z] if x >= 0. |
| const psimd_f32 vz = psimd_abs_f32(vx); |
| |
| // Compute reduced argument n := round(-z / log(2)). |
| // We do it by adding a large number (magic bias), which cause rounding of result to an integer, then subtracing the |
| // large number back. The first addition is combined with multiplication by log2e into a single FMA instruction. |
| // The trick with adding large number is valid only within certain bounds (|x| <= 2**22), but thats ok, because |
| // inputs x outside of [-87.336544, 17.328678] (i.e. z outsize [0, 87.336544]) underflow or saturate sigmoidf(x) |
| // anyway. We fixup the result for such inputs at the very end of the algorithm. |
| psimd_f32 vn = psimd_qfma_f32(vmagic_bias, vz, vminus_log2e); |
| |
| // Create a floating-point number s (scale) such that s == 2**n for inputs which don't cause underflow, i.e. |
| // -87.336544 <= -z <= 0.0, and -126 <= n <= 0 accordingly. |
| const psimd_f32 vs = (psimd_f32) ((psimd_u32) vn << 23); |
| |
| // Subtract the large number back to get the final n := round(-z / log(2)) as a floating-point number. |
| vn = psimd_sub_f32(vn, vmagic_bias); |
| |
| // Compute reduced argument t := z + n * log(2). Note that -t = -z - n * log(2). |
| // Use Cody-Waite range reduction method (note two constants to represent log(2)) to improve accuracy. |
| psimd_f32 vt = psimd_qfma_f32(vz, vn, vln2_hi); |
| vt = psimd_qfma_f32(vt, vn, vln2_lo); |
| |
| // Compute degree-5 polynomial approximation for exp(-t) on [-log(2)/2, log(2)/2]: |
| // P5(t) = 1 + t * (c1 + t * (c2 + t * (c3 + t * (c4 + t * c5)))) |
| psimd_f32 vp = psimd_qfma_f32(vc4, vt, vc5); |
| vp = psimd_qfma_f32(vc3, vt, vp); |
| vp = psimd_qfma_f32(vc2, vt, vp); |
| vp = psimd_qfma_f32(vc1, vt, vp); |
| |
| // Reconstruct the exp(-z) value: |
| // e = s * (1 + t * (c1 + t * (c2 + t * (c3 + t * (c4 + t * c5))))) |
| // = s + (t * s) * (c1 + t * (c2 + t * (c3 + t * (c4 + t * c5)))) |
| // = s + (t * s) * p |
| vt = psimd_mul_f32(vt, vs); |
| const psimd_f32 ve = psimd_qfma_f32(vs, vt, vp); |
| |
| // Reconstruct sigmoid(-z) = exp(-z) / (1.0 + exp(-z)) |
| psimd_f32 vf = psimd_div_f32(ve, psimd_add_f32(ve, vone)); |
| |
| // For inputs above denormal cutoff, replace output with +0.0f. |
| // Note that for NaN inputs, comparison result is false, and outputs are left unchanged. |
| vf = psimd_andnotmask_f32(vz > vdenorm_cutoff, vf); |
| |
| // Reconstruct sigmoid(x) = x < 0 ? sigmoid(-z) : 1.0 - sigmoid(-z) |
| vf = psimd_signblend_f32(vx, vf, psimd_sub_f32(vone, vf)); |
| |
| if (n & (2 * sizeof(float))) { |
| psimd_store2_f32(y, vf); |
| vf = psimd_concat_hi_f32(vf, vf); |
| y += 2; |
| } |
| if (n & (1 * sizeof(float))) { |
| psimd_store1_f32(y, vf); |
| } |
| } |
| } |