ncnn

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// Tencent is pleased to support the open source community by making ncnn available.
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//
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// Copyright (C) 2019 THL A29 Limited, a Tencent company. All rights reserved.
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//
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// Licensed under the BSD 3-Clause License (the "License"); you may not use this file except
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// in compliance with the License. You may obtain a copy of the License at
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//
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// https://opensource.org/licenses/BSD-3-Clause
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//
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// Unless required by applicable law or agreed to in writing, software distributed
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// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
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// CONDITIONS OF ANY KIND, either express or implied. See the License for the
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// specific language governing permissions and limitations under the License.
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#version 450
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#if NCNN_fp16_storage
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#extension GL_EXT_shader_16bit_storage: require
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#endif
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#if NCNN_fp16_arithmetic
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#extension GL_EXT_shader_explicit_arithmetic_types_float16: require
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#endif
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layout (constant_id = 0) const int clip = 0;
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layout (constant_id = 1) const float offset = 0;
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layout (constant_id = 2) const int num_sizes = 0;
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layout (constant_id = 3) const int num_ratios = 0;
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layout (constant_id = 4) const int num_prior = 0;
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#define shape_constant_id_offset 5
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layout (constant_id = shape_constant_id_offset + 0) const int w = 0;
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layout (constant_id = shape_constant_id_offset + 1) const int h = 0;
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layout (binding = 0) writeonly buffer top_blob { sfpvec4 top_blob_data[]; };
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layout (binding = 1) readonly buffer min_sizes { sfp min_sizes_data[]; };
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layout (binding = 2) readonly buffer aspect_ratios { sfp aspect_ratios_data[]; };
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layout (push_constant) uniform parameter
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{
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    int w;
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    int h;
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    float step_w;
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    float step_h;
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} p;
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void main()
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{
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    int gx = int(gl_GlobalInvocationID.x);
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    int gy = int(gl_GlobalInvocationID.y);
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    int gz = int(gl_GlobalInvocationID.z);
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    if (gx >= num_sizes || gy >= psc(w) || gz >= psc(h))
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        return;
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    // mxnet style _contrib_MultiBoxPrior
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    int v_offset = (gz * psc(w) + gy) * num_prior + gx;
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    afp center_x = (afp(gy) + afp(offset)) * afp(p.step_w);
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    afp center_y = (afp(gz) + afp(offset)) * afp(p.step_h);
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    afpvec4 center = afpvec4(center_x, center_y, center_x, center_y);
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    // ratio = 1, various sizes
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    afp size = buffer_ld1(min_sizes_data, gx);
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    afp cw = size * afp(0.5f) * afp(psc(h)) / afp(psc(w));
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    afp ch = size * afp(0.5f);
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    afpvec4 box = center + afpvec4(-cw, -ch, cw, ch);
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    box = clip == 1 ? clamp(box, afp(0.f), afp(1.f)) : box;
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    buffer_st4(top_blob_data, v_offset, box);
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    if (gx == 0)
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    {
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        // various ratios, size = min_size = size[0]
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        for (int pi = 1; pi < num_ratios; pi++)
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        {
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            afp v = buffer_ld1(aspect_ratios_data, pi);
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            afp cwr = cw * sqrt(v);
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            afp chr = ch / sqrt(v);
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            afpvec4 box = center + afpvec4(-cwr, -chr, cwr, chr);
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            box = clip == 1 ? clamp(box, afp(0.f), afp(1.f)) : box;
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            buffer_st4(top_blob_data, v_offset + num_sizes - 1 + pi, box);
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        }
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    }
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}
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