mdarray_examples

mdarray_examples — multi-dimensional arrays (Enhancement-15)

Demonstrates Verilog-A multi-dimensional array support, using version11's own openvaf-r and ngspice-46. Enhancement-15 generalises the 1-D arrays of Enhancement-14 to any number of dimensions:

Capability	Syntax
N-D declaration (variable & parameter)	real [0:1][0:2] m; · parameter real [0:1][0:1] w = ...;
N-D constant indexing (read/write)	m[0][1] = ...; · ... m[1][2]
Nested aggregate literals	acc = '{'{a, b}, '{c, d}};
N-D dynamic indexing (read/write)	tr[j][i] = acc[i][j]; in nested for loops
N-D array parameters (per-element default + override)	.model m mdarray_demo(w[1][1]=0.9)

mdarray_demo.va is a weighted-gain buffer: V(out) = gain * V(in), where the gain is the sum of a 2×2 weight matrix, computed through the multi-dim machinery. So measuring V(out) at V(in)=1 reads the gain back directly.

Run

python3 verify_mdarray.py

Expected:

default w='{'{0.1,0.2},'{0.3,0.4}}           1.000000     1.000000  PASS
override w[1][1]=0.9                         1.500000     1.500000  PASS
override w[0][0]=0.5 w[1][1]=0.5             1.500000     1.500000  PASS
ALL PASS

Notes

• Declaration is ranges-before-name: real [0:1][0:2] m; (2×3), one [msb:lsb] clause per dimension. Access is brackets-after-name: m[i][j].
• Element order / literal fill is row-major: the outermost dimension varies slowest, each dimension iterated msb→lsb. So real [0:1][0:2] m = '{'{a,b,c},'{d,e,f}} maps m[0][0]=a … m[1][2]=f.
• Array parameters expand into one scalar OSDI parameter per element, named w[0][0], w[0][1], … — ngspice overrides each individually in a .model card; unset elements keep their nested-literal default.
• Dynamic indexing applies to array variables. A dynamic index lowers to a runtime select over the flattened element variables (flat position Σ pos_k·stride_k), so its cost grows with the total element count — fine for the small coefficient matrices these features target. Array parameters are constant tables, indexed by a constant index (copy into a variable array to index dynamically, as mdarray_demo does).
• Number of [..] clauses must match the declared dimensionality, else a "wrong number of array indices" error is reported.