Neo4J post update.

2 files changed, 29 insertions, 24 deletions

diff --git a/_site/log/e-reader/index.html b/_site/log/e-reader/index.html
index 23d409b..a5dbc01 100644
--- a/_site/log/e-reader/index.html
+++ b/_site/log/e-reader/index.html
@@ -46,25 +46,26 @@
   <source src="ereader.mp4" type="video/mp4" />
 </video>
 
-<p>ESP-WROOM-32, 7.5” Waveshare e-paper display, three buttons (prev/next/sleep).</p>
+<p>System: ESP-WROOM-32, 7.5” Waveshare e-paper display, three buttons
+(prev/next/sleep).</p>
 
-<p>No local storage—streams books over HTTP. RTC memory tracks reading progress
-between sessions.</p>
+<p>2023-09-23: 512KB SRAM, 4MB flash (shared with FreeRTOS and ESP-IDF). Not
+enough storage for books. Using ESP32’s built-in WiFi to stream them over HTTP.
+Recording the reading progress in RTC memory.</p>
 
-<p>ESP32: 512KB SRAM, 4MB flash (shared with FreeRTOS, ESP-IDF). Not enough to
-store books. Stream from webserver instead.</p>
+<p>Rasterized pages encoded as tightly packed bitmaps (1 byte =&gt; 8 pixels), no
+headers, arranged along 48 KB (480x800) boundaries; Reader can stream pages
+using HTTP Range requests with zero server-side logic. Keeps both ends lean.</p>
 
-<p>Custom EBM file format. Rasterized monochrome bitmaps, one per page (480x800).
-One byte = 8 pixels. Pages on 48KB boundaries—HTTP Range requests work without
-server logic. pdftoebm.py converts PDFs.</p>
+<p>Page table stores 3 pages (prev/current/next) in a circular buffer. When the
+user requests a page, program cycles through the table, updates the screen, and
+downloads the next page.</p>
 
-<p>Circular buffer holds 3 pages (prev/current/next)–page table. Single-threaded
-approach too slow—user input, SPI, and HTTP on one core causes lag.</p>
+<p>Responsiveness is inadequate. Scheduling GPIO (user input), SPI, and HTTP on
+one core causes input lag. Pinned the GPIO and SPI tasks to one core, the HTTP
+task to the other core.</p>
 
-<p>Optimizations: pin the GPIO task (responding to user input and updating
-display) to one core, pin the HTTP task to the other core.</p>
-
-<p>Better, but system unresponsive during screen updates. Made SPI transfer async:</p>
+<p>Better, but screen updates are blocking user input; Made SPI transfer async:</p>
 
 <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>void epd_draw_async(const uint8_t *buf, size_t n)
 {
@@ -92,11 +93,14 @@ display) to one core, pin the HTTP task to the other core.</p>
 }
 </code></pre></div></div>
 
-<p>Much better. Squeeze a few more cycles by moving SPI buffer to DMA.</p>
+<p>Much better.</p>
+
+<p>2023-10-06: Moved the page table to DMA-capable memory; Reclaimed a few more
+CPU cycles from the SPI transfers.</p>
 
 <p>Can’t think of anything else.</p>
 
-<p>Outcome: Works but limited. Led to <a href="../etlas/">Etlas</a>.</p>
+<p>Verdict: Works but limited. Led to <a href="../etlas/">Etlas</a>.</p>
 
 <p>Commit:
 <a href="https://git.asciimx.com/esp32-e-reader/commit/?id=7f691c46093933b67aab466c0ca582ace8ab73d4">7f691c4</a></p>
diff --git a/_site/log/neo4j-a-star-search/index.html b/_site/log/neo4j-a-star-search/index.html
index 00f7886..c8c4ce6 100644
--- a/_site/log/neo4j-a-star-search/index.html
+++ b/_site/log/neo4j-a-star-search/index.html
@@ -40,13 +40,11 @@
           <h2 class="center" id="title">NEO4J SHORTEST PATH OPTIMIZATION</h2>
           <h5 class="center">06 MARCH 2018</h5>
           <br>
-          <div class="twocol justify"><p>Replaced Dijkstra’s search for vessel route tracking in Neo4J.</p>
+          <div class="twocol justify"><p>Work project. Marine vessel tracking with Neo4J hit a limit. Need to store
+13,000 route points; Dijkstra’s shortest path search slows after 4,000.</p>
 
-<p>Tracking 13,000 marine vessel route points. Needed shortest paths between ports
-for arrival prediction. Neo4j’s Dijkstra’s algorithm slows after 4,000 route
-points.</p>
-
-<p>Implemented A* search using haversine function as heuristic:</p>
+<p>Replaced Dijkstra’s algorithm with A* search using haversine function as
+heuristic:</p>
 
 <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>private double computeHeuristic(
     final double lat1, final double lon1,
@@ -84,8 +82,11 @@ points.</p>
 }
 </code></pre></div></div>
 
-<p>Outcome: 300x speedup. Scaled to 13,000 route points. Upstreamed changes. <a href="https://github.com/neo4j-contrib/neo4j-graph-algorithms/releases/tag/3.4.0.0" class="external" target="_blank" rel="noopener noreferrer">Neo4J v3.4.0</a>.
-<a href="https://github.com/neo4j-contrib/neo4j-graph-algorithms/blob/bd9732d9a690319552e134708692acb5a0d6b37c/algo/src/main/java/org/neo4j/graphalgo/impl/ShortestPathAStar.java">Full source</a></p>
+<p>Outcome: 300x speedup. Scaled to 13,000 route points.</p>
+
+<p>Upstreamed changes: <a href="https://github.com/neo4j-contrib/neo4j-graph-algorithms/releases/tag/3.4.0.0" class="external" target="_blank" rel="noopener noreferrer">Neo4J v3.4.0</a> | 
+<a href="https://github.com/neo4j-contrib/neo4j-graph-algorithms/blob/bd9732d9a690319552e134708692acb5a0d6b37c/algo/src/main/java/org/neo4j/graphalgo/impl/ShortestPathAStar.java">Full
+source</a></p>
 </div>
           <p class="post-author right">by W. D. Sadeep Madurange</p>
         </div>