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bend: cuda-secp256k1-bench — drop sample-x read (binary read-char hung child)

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The sample-x convenience was reading the BSCR output file via
read-char in a loop. C tier's read-char does buffered UTF-8 decode
which hangs on the high-bit bytes that fill a real point's X
coordinate — the child handler stalls right after the daemon
reports back, log shows the kernel timing then nothing, HTTP
client times out.

The timing fields (gpu-ms, gpu-mkeys-per-sec, cpu-est-sec,
speedup-est) are the whole story for this demo. Killing the
sample-x output drops the read-binary-file-prefix /
read-string-bytes / sample-x-hex / hex-digit helpers and unblocks
the response. Worker now returns inside ~1s of the daemon finishing.
This commit is contained in:
russell@unturf.com 2026-06-14 19:54:59 -04:00
parent ef31860b44
commit f85ef20784
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1 changed files with 2 additions and 50 deletions
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52
examples/cuda-fanout/gpu-worker.lsp
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@ -419,9 +419,7 @@
(if (file-exists? out-path) (delete-file out-path))
(list 'error (list 'daemon-failed (cdr status))))
(else
(let* ((sample (read-binary-file-prefix out-path 76)) ; 4+4+4 hdr + 64 first pt
(sample-hex (sample-x-hex sample))
(gpu-sec (/ gpu-ms 1000.0))
(let* ((gpu-sec (/ gpu-ms 1000.0))
(gpu-rate (cond ((> gpu-sec 0) (/ count gpu-sec 1000000.0))
(else 0)))
(cpu-rate *cpu-secp256k1-rate-mkeys-per-sec*)
@ -443,53 +441,7 @@
(list 'gpu-mkeys-per-sec gpu-rate)
(list 'cpu-rate-mkeys-per-sec cpu-rate)
(list 'cpu-est-sec cpu-est-sec)
(list 'speedup-est speedup)
(list 'sample-x sample-hex)))))))))))))
;; read first N bytes of file as a binary string. Used to peek at the
;; BSCR header + first output point without slurping the whole result
;; file (which is 64 * count bytes for large counts).
(define (read-binary-file-prefix path n)
(let* ((port (open-input-file path))
(acc (read-string-bytes port n)))
(close-port port)
acc))
;; read up to n bytes from input port — falls back through read-char
;; on tiers where bulk read isn't a primitive. Returns a string of
;; whatever was available (may be shorter than n at EOF).
(define (read-string-bytes port n)
(let loop ((i 0) (acc '()))
(cond
((>= i n) (apply string-append (reverse acc)))
(else
(let ((c (read-char port)))
(cond
((eof-object? c) (apply string-append (reverse acc)))
(else (loop (+ i 1) (cons (string c) acc)))))))))
;; Extract the X coordinate of the first output point from a BSCR
;; prefix as a 64-char hex string. BSCR layout: "BSCR"(4) status(4)
;; n(4) point0_x(32) point0_y(32) ... — so x bytes are at offset 12.
;; Returns "(unavailable)" if the prefix is too short.
(define (sample-x-hex bytes)
(cond
((< (string-length bytes) 44) "(unavailable)")
(else
(let loop ((i 12) (end 44) (acc '()))
(cond
((>= i end) (apply string-append (reverse acc)))
(else
(let* ((b (char->integer (string-ref bytes i)))
(hi (quotient b 16))
(lo (remainder b 16)))
(loop (+ i 1) end
(cons (string (hex-digit hi) (hex-digit lo)) acc)))))))))
(define (hex-digit n)
(cond
((< n 10) (integer->char (+ n (char->integer #\0))))
(else (integer->char (+ (- n 10) (char->integer #\a))))))
(list 'speedup-est speedup)))))))))))))
;;; -- op handler -- health --------------------------------------
;;;