einsum-style low-level API for general tensor product

proposal_product.md

@@ -0,0 +1,38 @@
+```c
+/// C := alpha A * B + beta C
+void product(
+   type typeA, int RankA,  int[] ExtA,  int[] StrideA,  void *A,  int[]
+idxA,
+   type typeB, int RankB,  int[] ExtB,  int[] StrideB,  void *B,  int[]
+idxB,
+   type typeC, int RankC,  int[] ExtC,  int[] StrideC,  void *C,  int[]
+idxC,
+   type type_alpha, void *alpha,
+   type type_beta,  void *beta,
+   void *context,  void *INOUT
+);
+```
+
+*NOTES*
+- all arrays are const, except from *C
+- type compute -> context
+   default: compute type = typeC
+- all int's are int64
+- aliasing?!
+
+refinement with explicit compute type
+```c
+void product_vPaul(
+   type typeA, int RankA,  int[] ExtA,  int[] StrideA,  void *A,  int[]
+idxA,
+   type typeB, int RankB,  int[] ExtB,  int[] StrideB,  void *B,  int[]
+idxB,
+   type typeC, int RankC,  int[] ExtC,  int[] StrideC,  void *C,  int[]
+idxC,
+   type type_alpha, void *alpha,
+   type type_beta,  void *beta,
+   compute_type type,
+   const void *infoIN,  void *infoOUT
+);
+```
+