fix mdconv backward bug (#563)

mmcv/ops/csrc/parrots/modulated_deform_conv_cuda.cu

@@ -273,20 +273,57 @@ void ModulatedDeformConvBackwardCUDAKernelLauncher(
     }
 
     for (size_t g = 0; g < group; g++) {
-      auto grad_weight_g = grad_weight[g].view(
-          {grad_weight.dim(1),
-           grad_weight.dim(2) * grad_weight.dim(3) * grad_weight.dim(4)});
-      gemm(ctx, 1, false,
-           grad_output[b][g].view(
-               {grad_output.dim(2), grad_output.dim(3) * grad_output.dim(4)}),
-           true, columns[g], 1, grad_weight_g);
+      auto grad_weight_g = ctx.createDArrayLite(
+          grad_weight.elemType(),
+          DArrayShape(grad_weight.dim(1), grad_weight.dim(2),
+                      grad_weight.dim(3), grad_weight.dim(4)));
+      copy(ctx, grad_weight_g, grad_weight[g]);
+      grad_weight_g = grad_weight_g.view(
+          {grad_weight_g.dim(0),
+           grad_weight_g.dim(1) * grad_weight_g.dim(2) * grad_weight_g.dim(3)});
+
+      auto columns_g = columns[g];
+      columns_g = transpose(ctx, columns_g, 0, 1);
+
+      auto grad_output_bg = ctx.createDArrayLite(
+          grad_output.elemType(),
+          DArrayShape(grad_output.dim(2), grad_output.dim(3),
+                      grad_output.dim(4)));
+      copy(ctx, grad_output_bg, grad_output[b][g]);
+      grad_output_bg =
+          grad_output_bg.view({grad_output_bg.dim(0),
+                               grad_output_bg.dim(1) * grad_output_bg.dim(2)});
+
+      grad_weight_g = parrots::op::addmm(ctx, grad_weight_g, grad_output_bg,
+                                         columns_g, 1, 1);
+      auto grad_weight_out = grad_weight[g];
+      copy(ctx, grad_weight_out, grad_weight_g);
 
       if (with_bias) {
-        auto grad_bias_g = grad_bias[g].view({grad_bias.dim(1), 1});
-        gemm(ctx, 1, false,
-             grad_output[b][g].view(
-                 {grad_output.dim(2), grad_output.dim(3) * grad_output.dim(4)}),
-             false, ones.view({ones.dim(0) * ones.dim(1), 1}), 1, grad_bias_g);
+        auto grad_bias_g = ctx.createDArrayLite(grad_bias.elemType(),
+                                                DArrayShape(grad_bias.dim(1)));
+        copy(ctx, grad_bias_g, grad_bias[g]);
+        grad_bias_g = grad_bias_g.view({grad_bias_g.dim(0), 1});
+
+        auto grad_output_bg = ctx.createDArrayLite(
+            grad_output.elemType(),
+            DArrayShape(grad_output.dim(2), grad_output.dim(3),
+                        grad_output.dim(4)));
+        copy(ctx, grad_output_bg, grad_output[b][g]);
+        grad_output_bg = grad_output_bg.view(
+            {grad_output_bg.dim(0),
+             grad_output_bg.dim(1) * grad_output_bg.dim(2)});
+
+        auto ones_g = ctx.createDArrayLite(
+            ones.elemType(), DArrayShape(ones.dim(0), ones.dim(1)));
+        copy(ctx, ones_g, ones);
+        ones_g = ones_g.view({ones_g.dim(0) * ones_g.dim(1), 1});
+
+        grad_bias_g =
+            parrots::op::addmm(ctx, grad_bias_g, grad_output_bg, ones_g, 1, 1);
+
+        auto grad_bias_out = grad_bias[g];
+        copy(ctx, grad_bias_out, grad_bias_g);
       }
     }