handle pnnx half weight when converting to ncnn

tools/pnnx/src/CMakeLists.txt

@@ -254,6 +254,7 @@ set(pnnx_pass_level5_SRCS
 set(pnnx_pass_ncnn_SRCS
     pass_ncnn/convert_attribute.cpp
     pass_ncnn/convert_custom_op.cpp
+    pass_ncnn/convert_half_to_float.cpp
     pass_ncnn/convert_input.cpp
     pass_ncnn/convert_torch_cat.cpp
     pass_ncnn/convert_torch_chunk.cpp

tools/pnnx/src/pass_ncnn.cpp

@@ -16,6 +16,7 @@
 
 #include "pass_ncnn/convert_attribute.h"
 #include "pass_ncnn/convert_custom_op.h"
+#include "pass_ncnn/convert_half_to_float.h"
 #include "pass_ncnn/convert_input.h"
 #include "pass_ncnn/convert_torch_cat.h"
 #include "pass_ncnn/convert_torch_chunk.h"
@@ -73,6 +74,8 @@ void pass_ncnn(Graph& g)
 
     ncnn::solve_batch_index(g);
 
+    ncnn::convert_half_to_float(g);
+
     int opindex = 0;
     for (auto x : g_global_pnnx_ncnn_graph_rewriter_passes)
     {

tools/pnnx/src/pass_ncnn/convert_half_to_float.cpp

@@ -0,0 +1,115 @@
+// Tencent is pleased to support the open source community by making ncnn available.
+//
+// Copyright (C) 2022 THL A29 Limited, a Tencent company. All rights reserved.
+//
+// Licensed under the BSD 3-Clause License (the "License"); you may not use this file except
+// in compliance with the License. You may obtain a copy of the License at
+//
+// https://opensource.org/licenses/BSD-3-Clause
+//
+// Unless required by applicable law or agreed to in writing, software distributed
+// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
+// CONDITIONS OF ANY KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations under the License.
+
+#include "convert_half_to_float.h"
+
+namespace pnnx {
+
+namespace ncnn {
+
+static float float16_to_float32(unsigned short value)
+{
+    // 1 : 5 : 10
+    unsigned short sign = (value & 0x8000) >> 15;
+    unsigned short exponent = (value & 0x7c00) >> 10;
+    unsigned short significand = value & 0x03FF;
+
+    //     NCNN_LOGE("%d %d %d", sign, exponent, significand);
+
+    // 1 : 8 : 23
+    union
+    {
+        unsigned int u;
+        float f;
+    } tmp;
+    if (exponent == 0)
+    {
+        if (significand == 0)
+        {
+            // zero
+            tmp.u = (sign << 31);
+        }
+        else
+        {
+            // denormal
+            exponent = 0;
+            // find non-zero bit
+            while ((significand & 0x200) == 0)
+            {
+                significand <<= 1;
+                exponent++;
+            }
+            significand <<= 1;
+            significand &= 0x3FF;
+            tmp.u = (sign << 31) | ((-exponent + (-15 + 127)) << 23) | (significand << 13);
+        }
+    }
+    else if (exponent == 0x1F)
+    {
+        // infinity or NaN
+        tmp.u = (sign << 31) | (0xFF << 23) | (significand << 13);
+    }
+    else
+    {
+        // normalized
+        tmp.u = (sign << 31) | ((exponent + (-15 + 127)) << 23) | (significand << 13);
+    }
+
+    return tmp.f;
+}
+
+void convert_half_to_float(Graph& graph)
+{
+    for (Operator* op : graph.ops)
+    {
+        while (1)
+        {
+            bool matched = false;
+
+            for (auto x : op->attrs)
+            {
+                const Attribute& attr = x.second;
+                if (attr.type != 3)
+                    continue;
+
+                matched = true;
+
+                // fp16 -> fp32
+                Attribute attr_new;
+                attr_new.type = 1;
+                attr_new.shape = attr.shape;
+                attr_new.data.resize(attr.data.size() * 2);
+
+                const unsigned short* p = (const unsigned short*)attr.data.data();
+                float* outp = (float*)attr_new.data.data();
+                int len = attr_new.data.size() / 4;
+                for (int i = 0; i < len; i++)
+                {
+                    outp[i] = float16_to_float32(p[i]);
+                }
+
+                op->attrs[x.first] = attr_new;
+
+                break;
+            }
+
+            if (!matched)
+                break;
+        }
+    }
+}
+
+} // namespace ncnn
+
+} // namespace pnnx

tools/pnnx/src/pass_ncnn/convert_half_to_float.h

@@ -0,0 +1,25 @@
+// Tencent is pleased to support the open source community by making ncnn available.
+//
+// Copyright (C) 2022 THL A29 Limited, a Tencent company. All rights reserved.
+//
+// Licensed under the BSD 3-Clause License (the "License"); you may not use this file except
+// in compliance with the License. You may obtain a copy of the License at
+//
+// https://opensource.org/licenses/BSD-3-Clause
+//
+// Unless required by applicable law or agreed to in writing, software distributed
+// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
+// CONDITIONS OF ANY KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations under the License.
+
+#include "pass_ncnn.h"
+
+namespace pnnx {
+
+namespace ncnn {
+
+void convert_half_to_float(Graph& graph);
+
+} // namespace ncnn
+
+} // namespace pnnx