stillwater-sc / universal
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coverage: 85.418% (+0.05%) from 85.372%
32616940134

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perf(elreal): memoize the transcendental constants (#1384)

pi and ln2 were recomputed from scratch on every call. That -- not the series each
one wraps -- was essentially the entire cost of sin, cos, tan and log. Measured at
depth 8 on a double host, all reaching ~130 digits:

    pi_zbcl(8)   ALONE   371.90 ms        sin(0.5,8)  TOTAL   371.82 ms
    ln2_zbcl(8)  ALONE   373.17 ms        log(2,8)    TOTAL   375.61 ms
                                          exp(1,8)    TOTAL     9.57 ms
                                          sqrt(2,8)   TOTAL     4.04 ms

sin cost what pi_zbcl cost, to within noise. exp and sqrt need no constant, which is
exactly why they were two orders of magnitude cheaper. pi_zbcl ran two full
odd_power_series evaluations (Machin) per call, with nothing retained.

Cached per (FpType, depth), thread_local. In steady state:

    function     before     after
    sin / cos    ~372 ms    ~5.8 ms
    tan           374 ms    ~9.1 ms
    log           374 ms    ~0.01 ms
    exp, sqrt    unchanged  unchanged

The first call at a given depth still pays for the constant. Memoized: e, ln2, ln10,
log2_10, pi, sqrt2/3/5, phi, euler_gamma.

KEYED ON THE EXACT DEPTH, and that is the constraint worth recording. Caching the
deepest value and truncating it for shallower requests is cheaper, and it is what I
proposed on the issue before measuring. It is wrong: these constants are NOT
prefix-stable. pi at depth 2 differs from take(2) of pi at depth 8 after ~32 digits,
because the deeper evaluation refines the last block rather than merely extending it.
Under that scheme pi_zbcl(2) would return one value or another depending on whether
some unrelated earlier call had asked for more -- results that depend on call
history, which a numeric library cannot do.

Values are unchanged: the first call at a depth computes exactly what it computed
before, and later calls return that same object.

Regression constant_memoization.cpp guards both properties, c... (continued)

45 of 45 new or added lines in 1 file covered. (100.0%)

43182 of 50554 relevant lines covered (85.42%)

7151229.37 hits per line

Relevant lines Covered
50554 RELEVANT LINES 43182 COVERED LINES
7151229.37 HITS PER LINE
Source Files on Ravenwater-patch-1

Recent builds

Builds Branch Commit Type Ran Committer Via Coverage
32616940134 main perf(elreal): memoize the transcendental constants (#1384) pi and ln2 were recomputed from scratch on every call. That -- not the series each one wraps -- was essentially the entire cost of sin, cos, tan and log. Measured at depth 8 on a double h... push web-flow github
85.42
32615585723 perf/issue-1383-memoize-constants Merge f98e69881 into 6fe71a71d Pull #1384 web-flow github
85.42
32610739250 main feat(elreal): evidence-based precision defaults, and fix what the sweep exposed (#1382) Resolves #1177 by running the characterization tool (#1040) and acting on what it measured. The answer is not the one the issue anticipated. THE PREMISE CHAN... push web-flow github
85.37
32608203672 feat/issue-1177-evidence-based-defaults Merge 4e717e6b7 into d1096b017 Pull #1382 web-flow github
85.37
32603809424 main fix(einteger): make the parse radix independent of the leading-zero count (#1381) * fix(einteger): make the parse radix independent of the leading-zero count parse() decided between octal and decimal in a way no caller could predict: a single le... push web-flow github
85.39
32603120347 fix/issue-1370-einteger-octal-radix Merge 76225c0b3 into 4d7ca1cd0 Pull #1381 web-flow github
85.37
32602939989 fix/issue-1370-einteger-octal-radix Merge 380855502 into 4d7ca1cd0 Pull #1381 web-flow github
85.39
32599692203 main feat(elreal): offer the faithful long division alongside the Newton reciprocal (#1380) For a DENSE (multi-block, non-power-of-two) divisor, div_online has computed a/b = a * (1/b) with a Newton-Raphson reciprocal since #1068 -- a deliberate devia... push web-flow github
85.37
32597652090 feat/issue-1061-faithful-long-division Merge 662f05a7a into e6aa3570b Pull #1380 web-flow github
85.37
32593773442 main fix(elreal): stop the lazy producers owning themselves (#1379) * fix(elreal): stop the lazy producers owning themselves add() and infsum() built their tail thunk as a std::function holding a shared_ptr to the control block that owned it. The fun... push web-flow github
85.41
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