by default, a linear chain without any forking is generated,
and the result hash is computed by hash-chaining from the seed.
Verify proper connections and validate computed hash
..as can be expected, had do chase down some quite hairy problems,
especially since consumption of the fixed amount of nodes is not
directly linked to the ''beat'' of the main loop and thus boundary
conditions and exhausted storage can happen basically anywhere.
Used a simple expansion rule and got a nod graph,
which looks coherent in DOT visualisation.
writing a control-value rule for topology generation typically
involves some modulus and then arthmetic operations to map
only part of the value range to the expected output range.
These calculations are generic, noisy and error-prone.
Thus introduce a helper type, which allows the client just
to mark up the target range of the provided value to map and
transform to the actually expected result range, including some
slight margin to absorb rounding errors. Moreover, all calculations
done in double, to avoid the perils of unsigned-wrap-around.
...these were developed driven by the immediate need
to visualise ''random generated computation patterns''
for ''Scheduler load testing.''
The abstraction level of this DSL is low
and structures closely match some clauses of the DOT language;
this approach may not yet be adequate to generate more complex
graph structures and was extracted as a starting point
for further refinements....
With all the preceding DSL work, this turns out to be surprisingly easy;
the only minor twist is the grouping of nodes into (time)levels,
which can be achieved with a "lagging" update from the loop body
Note: next step will be to extract the DSL helpers into a Library header
...using a pre-established example as starting point
It seems that building up this kind of generator code
from a set of free functions in a secluded namespace
is the way most suitable to the nature of the C++ language
..the idea is to generate a Graphviz-DOT diagram description
by traversing the internal data structures of TestChainLoad.
- refreshed my Graphviz knowledge
- work out a diagram scheme that can be easily generated
- explore ways to structure code generation as a DSL to keep it legible
...introduce statistical control functions (based on hash)
...add processing stage for current set of nodes
...process forking, reduction and injection of new nodes
- use a specialised class, layered on top of std::array
- use additional storage to mark filling degree
- check/fail on link owerflow directly there
We still use fixed size inline storage for the node links,
yet adding this comparatively small overhead in storage helps
getting the code simpler and adding links is now constant-complexity
A »Node« represents one junction point in the dependency graph,
knows his predecessors and successors and carries out one step
of the chained hash calculation.
