PYTHON · NUMPY

Readout is the term you forgot

On metered silicon, how does reading a value back compare with computing it?

Price the readout of a relocated decision and show what it does to an advantage that omitted it.

01Challenge

Every claim you have checked so far priced the computing. None priced getting the answer out. On metered silicon the read costs sixty-four times the operation it reads.

Predict firstOn metered silicon, how does reading a value back compare with computing it?

02Model

An advantage that omits readout is bounded by the term it omitted. The Institute metered both ends on a Kria KV260: a node update costs 9.13 picojoules against a value read back at 581, so reading is sixty-four times the operating. The same omission is why a published thermodynamic advantage of ten to the eleventh collapses once each value read out has to be paid for, and it is the reason this course puts readout on its own axis rather than folding it into the model. A cost function with no readout term is not conservative; it is incomplete in one direction only.

03Guided practice

Compute the advantage with readout free, then charge the metered read, then find the read energy at which the advantage falls to one. That last number is what the claim was assuming without saying so.

04Feedback

PASS WHEN You showed the metered read changes the advantage, and stated the per-read energy at which relocation stops paying at all.

If your run fails, check:

An advantage that omits readout is bounded by the term it omitted.
Sixty-four to one is measured, not assumed.

05Retrieve & space

Why is readout the term most often left out of an energy claim?
Your break-even read is some multiple of kT ln 2. What would it mean if that multiple were below one?

06Mastery & project

You can price readout separately and say what a claim assumed about it.

Take a relocated decision in your own system. Count the values that have to cross back, and price them.

GO FURTHER · THE LIVE PLAYGROUND

What a decision costs: the instrument ↗ · Move the router and watch the ceiling move with it.
PAI-280 · Measuring Energy ↗ · Where to put the meter so the readout is inside the boundary.

← The decision that stays on the machine State it as a budget →

PYTHON · NUMPY

Readout is the term you forgot

Two metered numbers from the Institute's own FPGA, and one claim that never mentions the second.

You read

the arrays and values already in scope

You change

the code you write in each cell

Fixed

the dataset and the checks that grade you