Replace swich case with refCastFrom()

Much better inputs handling for the Slice, Gather and Reshape operators.

Current implementation will fail in each of these cases:

• Use of any other data type than float, double, int64 or int32 for the inputs;
• Inputs from another backend => operators not usable of GPU!

Also:

• The forwardDims() mechanism with the allowDataDependency argument was no used as intended. Output should never be resized in the Operator implementation. Actually, no memory allocation should be performed here. All dims must be known and allocated for the implementation;
• There was a huge bug in Tensor registration for Int64: type long was used, which is not garanteed to be 64-bits (it is not on MSVC!)

Please read carefully the changes to understand the intended way to handle output dims data dependent operators.

src/operator/Slice.cpp

@@ -36,33 +36,24 @@ void Aidge::Slice_OpImpl::forward() {
                  (op.template getAttr<SliceAttr::Starts>().size() == op.template getAttr<SliceAttr::Axes>().size()),
                  "start, end and axes arguments should be the same size.");
 
-    const std::size_t nbDims = op.getInput(0)->nbDims();
-
-    const std::vector<std::size_t>& inputDims = op.getInput(0)->dims();
-    auto outputDims = op.getInput(0)->dims();
+    const auto nbDims = op.getInput(0)->nbDims();
+    const auto& inputDims = op.getInput(0)->dims();
+    const auto& outputDims = op.getOutput(0)->dims();
 
     // compute index of the output's first element
-    // compute output dimension at the same time (may change between two forward calls)
     std::size_t beginning = 0;
     const std::size_t nbAxes = op.template getAttr<SliceAttr::Axes>().size();
     for (std::size_t i = 0; i < nbAxes; ++i) {
         // For each slice operation get the params and cast them to size_t
-        DimIdx_t axis = op.template getAttr<SliceAttr::Axes>()[i] >= 0 ?
+        const DimIdx_t axis = op.template getAttr<SliceAttr::Axes>()[i] >= 0 ?
                             static_cast<DimIdx_t>(op.template getAttr<SliceAttr::Axes>()[i]) :
                             static_cast<DimIdx_t>(op.template getAttr<SliceAttr::Axes>()[i] + static_cast<DimIdx_t>(inputDims.size()));
-        DimSize_t start = op.template getAttr<SliceAttr::Starts>()[i] >= 0 ?
+        const DimSize_t start = op.template getAttr<SliceAttr::Starts>()[i] >= 0 ?
                             static_cast<DimSize_t>(op.template getAttr<SliceAttr::Starts>()[i]) :
                             static_cast<DimSize_t>(op.template getAttr<SliceAttr::Starts>()[i] + static_cast<DimSize_t>(inputDims[axis]));
-        DimSize_t end = op.template getAttr<SliceAttr::Ends>()[i] >= 0 ?
-                        static_cast<DimSize_t>(op.template getAttr<SliceAttr::Ends>()[i]) :
-                        static_cast<DimSize_t>(op.template getAttr<SliceAttr::Ends>()[i] + static_cast<DimSize_t>(inputDims[axis]));
         const std::size_t stridePostAxis = std::accumulate(inputDims.cbegin()+axis+1, inputDims.cend(), std::size_t(1), std::multiplies<std::size_t>());
         beginning += start * stridePostAxis;
-        const std::size_t sliceLength = end - start;
-        outputDims[axis] = sliceLength;
     }
-    op.getOutput(0)->resize(outputDims);
-
 
     // for inputDims = {4,5,5,3} & outputDims = {3,2,2,1}: substractDims = {1,5,5,3}
     std::vector<std::size_t> substractedDims = std::vector<std::size_t>(nbDims);
@@ -195,16 +186,16 @@ bool Aidge::Slice_Op::forwardDims(bool allowDataDependency) {
 
     AIDGE_ASSERT(!this->template getAttr<SliceAttr::Axes>().empty(), "Missing input#3 or Axes attribute");
 
-    DimSize_t nbAxes = this->template getAttr<SliceAttr::Axes>().size();
+    const DimSize_t nbAxes = this->template getAttr<SliceAttr::Axes>().size();
     std::vector<DimSize_t> outDims = getInput(0)->dims();
     for (std::size_t i = 0; i < nbAxes; ++i) {
-        DimIdx_t axis = this->template getAttr<SliceAttr::Axes>()[i] >= 0 ?
+        const DimIdx_t axis = this->template getAttr<SliceAttr::Axes>()[i] >= 0 ?
                         static_cast<DimIdx_t>(this->template getAttr<SliceAttr::Axes>()[i]) :
                         static_cast<DimIdx_t>(this->template getAttr<SliceAttr::Axes>()[i] + static_cast<DimIdx_t>(getInput(0)->nbDims()));
-        DimSize_t start = this->template getAttr<SliceAttr::Starts>()[i] >= 0 ?
+        const DimSize_t start = this->template getAttr<SliceAttr::Starts>()[i] >= 0 ?
                             static_cast<DimSize_t>(this->template getAttr<SliceAttr::Starts>()[i]) :
                             static_cast<DimSize_t>(this->template getAttr<SliceAttr::Starts>()[i] + static_cast<DimSize_t>(getInput(0)->dims()[axis]));
-        DimSize_t end = this->template getAttr<SliceAttr::Ends>()[i] >= 0 ?
+        const DimSize_t end = this->template getAttr<SliceAttr::Ends>()[i] >= 0 ?
                         static_cast<DimSize_t>(this->template getAttr<SliceAttr::Ends>()[i]) :
                         static_cast<DimSize_t>(this->template getAttr<SliceAttr::Ends>()[i] + static_cast<DimSize_t>(getInput(0)->dims()[axis]));