# Adaptive RK7(8): results

The RK4 oscillator above is a fixed-step problem: every accepted step costs
the same arithmetic, and the four friction points (launch overhead, host
round trips, finished samples, idle lanes) show up against a constant
per-step cost. The second card runs the same class of problem through an
*adaptive* solver instead: a two-body Kepler orbit (float64, eccentricity
uniform in [0, 0.9]) integrated with Fehlberg's embedded RKF7(8) pair to
rtol = atol = 1e-10, so each sample also decides, step by step, whether to
accept or shrink -- a second, data-dependent source of per-sample
divergence on top of each sample's own stopping time. `eagle.simulate`
appears here too, running the same attempt kernel the hand-built `hawk + eagle
graph` arm uses, under its automatic launch policy.

Pick a device with the tabs; the table of every arm and every N is collapsed
under the chart. How to read the numbers: [Reading the numbers](reading.md).

## GPU

```{include} /content/_generated/rk78_card_gpu.md
```

## CPU

```{include} /content/_generated/rk78_card_cpu.md
```