From d2cc948831808f71ece17fda43afa89f27b920d0 Mon Sep 17 00:00:00 2001
From: Daryl Richter <daryl@ngzax.com>
Date: Fri, 15 Jul 2022 16:40:25 -0400
Subject: [PATCH 01/14] fix up an outdated comment

---
 pkg/vere/main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pkg/vere/main.c b/pkg/vere/main.c
index ec98561ea7..e7f06093f1 100644
--- a/pkg/vere/main.c
+++ b/pkg/vere/main.c
@@ -1888,7 +1888,7 @@ _cw_queu(c3_i argc, c3_c* argv[])
   }
 }
 
-/* _cw_uniq(): deduplicate persistent nouns
+/* _cw_meld(): deduplicate persistent nouns
 */
 static void
 _cw_meld(c3_i argc, c3_c* argv[])

From 86ed375492766e1458b5025dfee93b0590bfeccc Mon Sep 17 00:00:00 2001
From: Daryl Richter <daryl@ngzax.com>
Date: Fri, 15 Jul 2022 16:41:26 -0400
Subject: [PATCH 02/14] basic `melt` runner as a copy of `meld`

---
 pkg/vere/main.c | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/pkg/vere/main.c b/pkg/vere/main.c
index e7f06093f1..5e2b35bff8 100644
--- a/pkg/vere/main.c
+++ b/pkg/vere/main.c
@@ -718,6 +718,7 @@ _cw_usage(c3_c* bin_c)
     "  %s grab %.*s              measure memory usage:\n",
     "  %s info %.*s              print pier info:\n",
     "  %s meld %.*s              deduplicate snapshot:\n",
+    "  %s melt %.*s              deduplicate and minimize snapshot:\n",
     "  %s pack %.*s              defragment snapshot:\n",
     "  %s play %.*s              recompute events:\n",
     "  %s prep %.*s              prepare for upgrade:\n",
@@ -1976,6 +1977,44 @@ _cw_meld(c3_i argc, c3_c* argv[])
   u3m_stop();
 }
 
+/* _cw_melt(): deduplicate persistent nouns and compress them to minimal size
+*/
+static void
+_cw_melt(c3_i argc, c3_c* argv[])
+{
+  switch ( argc ) {
+    case 2: {
+      if ( !(u3_Host.dir_c = _main_pier_run(argv[0])) ) {
+        fprintf(stderr, "unable to find pier\r\n");
+        exit (1);
+      }
+    } break;
+
+    case 3: {
+      u3_Host.dir_c = argv[2];
+    } break;
+
+    default: {
+      fprintf(stderr, "invalid command\r\n");
+      exit(1);
+    } break;
+  }
+
+  u3_disk* log_u = _cw_disk_init(u3_Host.dir_c); // XX s/b try_aquire lock
+  c3_w     pre_w;
+
+  u3C.wag_w |= u3o_hashless;
+  u3m_boot(u3_Host.dir_c);
+
+  pre_w = u3a_open(u3R);
+  u3u_melt();
+  u3a_print_memory(stderr, "urbit: melt: gained", (u3a_open(u3R) - pre_w));
+
+  u3e_save();
+  u3_disk_exit(log_u);
+  u3m_stop();
+}
+
 /* _cw_next(): request upgrade
 */
 static void
@@ -2856,6 +2895,7 @@ _cw_utils(c3_i argc, c3_c* argv[])
 
     case c3__info: _cw_info(argc, argv); return 1;
     case c3__meld: _cw_meld(argc, argv); return 1;
+    case c3__melt: _cw_melt(argc, argv); return 1;
     case c3__next: _cw_next(argc, argv); return 2; // continue on
     case c3__pack: _cw_pack(argc, argv); return 1;
     case c3__play: _cw_play(argc, argv); return 1;

From 2c4a084dbd845309261c26a1523a4a6bb26c3795 Mon Sep 17 00:00:00 2001
From: Daryl Richter <daryl@ngzax.com>
Date: Thu, 21 Jul 2022 08:41:24 -0400
Subject: [PATCH 03/14] pseudocode impl of u3U_melt()

---
 pkg/noun/urth.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)

diff --git a/pkg/noun/urth.c b/pkg/noun/urth.c
index 701d235637..73bc4a99a8 100644
--- a/pkg/noun/urth.c
+++ b/pkg/noun/urth.c
@@ -460,6 +460,66 @@ u3u_meld(void)
 }
 #endif
 
+/* _cj_warm_tap(): tap war_p to rel
+*/
+static void
+_cj_warm_tap(u3_noun kev, void* wit)
+{
+  u3_noun* rel = wit;
+  *rel = u3nc(u3k(kev), *rel);
+}
+
+/* u3u_melt(): globally deduplicate memory.
+*/
+void
+u3u_melt(void)
+{
+  c3_assert( &(u3H->rod_u) == u3R ); // Make sure we're on the main road.
+
+  u3_noun cod = u3_nul; // cons list of cold jet registrations
+  u3h_walk_with(u3R->jed.cod_p, _cj_warm_tap, &cod);
+
+  u3m_reclaim(); // Throw away what we don't need
+  u3j_free(); // free cold & warm jet state
+
+  // NOTE: We are now in an invalid state.
+  // TODO: Free everything else we can. Joe to provide? Look at garbage collector - u3a->roc, u3a->jed, u3m_mark (mark all roots).
+
+  u3p(u3h_root) set_p = u3h_new();
+
+  cod = our_traversal(cod, set_p);
+  u3A->roc = our_traversal(u3A->roc, set_p);
+
+  u3h_free(set_p);
+
+  // Put the jet registrations back. Loop over cod putting them back into the cold jet
+  // dashboard. Then re-run the garbage collector.
+  u3j_boot(c3y);
+  u3_noun codc;
+  codc = cod;
+
+  u3R->jed.cod_p = u3h_new();
+  while(u3_nul != cod) {
+    u3_noun kev = u3h(cod);
+    u3h_put(u3R->jed.cod_p, u3h(kev), u3k(u3t(kev)));
+    cod = u3t(cod);
+  }
+  u3z(codc);
+
+  u3j_ream();  // re-init all the jets
+  u3m_pack();  // remove free space
+}
+
+/* our_traversal
+(a_noun, known_nouns)
+iterate known_nouns looking at the value of each one and seeing if the value of a_noun matches.
+if we find it, return the pointer to the value and decrement the ref count of a_noun if it's pointer is not.
+
+let foo = (get known_nouns a_noun)
+if ( foo != a_noun ) { lose(a_noun); return foo; }
+
+*/
+
 /* _cu_rock_path(): format rock path.
 */
 static c3_o

From bd329e284de8b0ed3b90818ee15c512ff43dfffb Mon Sep 17 00:00:00 2001
From: Daryl Richter <daryl@ngzax.com>
Date: Thu, 21 Jul 2022 16:56:06 -0400
Subject: [PATCH 04/14] initial jfb implementation

---
 pkg/noun/urth.c | 80 +++++++++++++++++++++++++++++++++++++++++++++----
 pkg/noun/urth.h |  5 ++++
 2 files changed, 79 insertions(+), 6 deletions(-)

diff --git a/pkg/noun/urth.c b/pkg/noun/urth.c
index 73bc4a99a8..1ef674e097 100644
--- a/pkg/noun/urth.c
+++ b/pkg/noun/urth.c
@@ -460,6 +460,9 @@ u3u_meld(void)
 }
 #endif
 
+/* BEGIN helper functions for u3u_meld
+   -------------------------------------------------------------------
+*/
 /* _cj_warm_tap(): tap war_p to rel
 */
 static void
@@ -469,14 +472,78 @@ _cj_warm_tap(u3_noun kev, void* wit)
   *rel = u3nc(u3k(kev), *rel);
 }
 
-/* u3u_melt(): globally deduplicate memory.
+static inline u3_weak
+_get(u3_noun som, u3p(u3h_root) set_p)
+{
+  u3_post hav_p = u3h_git(set_p, som);
+
+  if (u3_none == hav_p)
+  {
+    return u3_none;
+  }
+
+  //  restore tag bits from [som]
+  //
+  return hav_p | ((som >> 30) << 30);
+}
+
+static inline void
+_put(u3_noun som, u3p(u3h_root) set_p)
+{
+  //  strip tag bits from [som] to skip refcounts
+  //
+  u3_post hav_p = u3a_to_off(som);
+  u3h_put(set_p, u3k(som), hav_p);
+}
+
+static u3_noun
+_traverse(u3_noun som, u3p(u3h_root) set_p)
+{
+  u3_weak hav;
+
+  //  skip direct atoms
+  //
+  if (c3y == u3a_is_cat(som))
+  {
+    return som;
+  }
+
+  //  [som] equals [hav], and [hav] is canonical
+  //
+  if (u3_none != (hav = _get(som, set_p)))
+  {
+    u3z(som);
+    return u3k(hav);
+  }
+
+  //  traverse subtrees
+  //
+  if (c3y == u3a_is_cell(som))
+  {
+    u3a_cell *cel_u = u3a_to_ptr(som);
+
+    cel_u->hed = _traverse(cel_u->hed, set_p);
+    cel_u->tel = _traverse(cel_u->tel, set_p);
+  }
+
+  //  [som] is canonical
+  //
+  _put(som, set_p);
+  return som;
+}
+
+/* u3u_melt(): globally deduplicate memory and pack in-place.
 */
 void
 u3u_melt(void)
 {
-  c3_assert( &(u3H->rod_u) == u3R ); // Make sure we're on the main road.
+  // Verify that we're on the main road.
+  //
+  c3_assert( &(u3H->rod_u) == u3R );
 
-  u3_noun cod = u3_nul; // cons list of cold jet registrations
+  // Get a cons list of the cold jet registrations.
+  //
+  u3_noun cod = u3_nul;
   u3h_walk_with(u3R->jed.cod_p, _cj_warm_tap, &cod);
 
   u3m_reclaim(); // Throw away what we don't need
@@ -484,16 +551,17 @@ u3u_melt(void)
 
   // NOTE: We are now in an invalid state.
   // TODO: Free everything else we can. Joe to provide? Look at garbage collector - u3a->roc, u3a->jed, u3m_mark (mark all roots).
-
+  //
   u3p(u3h_root) set_p = u3h_new();
 
-  cod = our_traversal(cod, set_p);
-  u3A->roc = our_traversal(u3A->roc, set_p);
+  cod = _traverse(cod, set_p);
+  u3A->roc = _traverse(u3A->roc, set_p);
 
   u3h_free(set_p);
 
   // Put the jet registrations back. Loop over cod putting them back into the cold jet
   // dashboard. Then re-run the garbage collector.
+  //
   u3j_boot(c3y);
   u3_noun codc;
   codc = cod;
diff --git a/pkg/noun/urth.h b/pkg/noun/urth.h
index 0dc2aa8168..28a3019c61 100644
--- a/pkg/noun/urth.h
+++ b/pkg/noun/urth.h
@@ -12,6 +12,11 @@
         c3_w
         u3u_meld(void);
 
+      /* u3u_melt(): globally deduplicate memory and pack in-place.
+      */
+        void
+        u3u_melt(void);
+
       /* u3u_cram(): globably deduplicate memory, and write a rock to disk.
       */
         c3_o

From 5c229092f4fbc9df0649d45af90ea9adc0e8dffb Mon Sep 17 00:00:00 2001
From: Daryl Richter <daryl@ngzax.com>
Date: Fri, 22 Jul 2022 14:23:45 -0400
Subject: [PATCH 05/14] re-pave all the necessary road parts

---
 pkg/noun/urth.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/pkg/noun/urth.c b/pkg/noun/urth.c
index 1ef674e097..0bf5473f68 100644
--- a/pkg/noun/urth.c
+++ b/pkg/noun/urth.c
@@ -563,6 +563,7 @@ u3u_melt(void)
   // dashboard. Then re-run the garbage collector.
   //
   u3j_boot(c3y);
+
   u3_noun codc;
   codc = cod;
 
@@ -574,6 +575,12 @@ u3u_melt(void)
   }
   u3z(codc);
 
+  // We threw these away so we need to re-pave them before re-initialization.
+  //
+  u3R->jed.bas_p = u3h_new();
+  u3R->jed.han_p = u3h_new();
+  u3R->jed.war_p = u3h_new();
+
   u3j_ream();  // re-init all the jets
   u3m_pack();  // remove free space
 }

From c0dbd9926815c54524be8378a17733573d8c6bde Mon Sep 17 00:00:00 2001
From: Daryl Richter <daryl@ngzax.com>
Date: Fri, 22 Jul 2022 15:28:48 -0400
Subject: [PATCH 06/14] refactor/extract-method

consolidates re-initializing the jet dashboard
hashtables into a public method for reuse.
---
 pkg/noun/manage.c | 24 ++++++++++++++++++++----
 pkg/noun/manage.h |  5 +++++
 pkg/noun/urth.c   | 11 ++++-------
 3 files changed, 29 insertions(+), 11 deletions(-)

diff --git a/pkg/noun/manage.c b/pkg/noun/manage.c
index d880a42032..c7c80cee95 100644
--- a/pkg/noun/manage.c
+++ b/pkg/noun/manage.c
@@ -470,6 +470,17 @@ u3m_mark(FILE* fil_u)
   return tot_w;
 }
 
+/* _pave_jets(): build jet tables.
+*/
+static void
+_pave_jets(void)
+{
+  u3R->jed.bas_p = u3h_new();
+  u3R->jed.cod_p = u3h_new();
+  u3R->jed.han_p = u3h_new();
+  u3R->jed.war_p = u3h_new();
+}
+
 /* _pave_parts(): build internal tables.
 */
 static void
@@ -477,11 +488,8 @@ _pave_parts(void)
 {
   u3R->cax.har_p = u3h_new_cache(u3C.hap_w);  //  transient
   u3R->cax.per_p = u3h_new_cache(u3C.per_w);  //  persistent
-  u3R->jed.war_p = u3h_new();
-  u3R->jed.cod_p = u3h_new();
-  u3R->jed.han_p = u3h_new();
-  u3R->jed.bas_p = u3h_new();
   u3R->byc.har_p = u3h_new();
+  _pave_jets();
 }
 
 /* _pave_road(): writes road boundaries to loom mem (stored at mat_w)
@@ -675,6 +683,14 @@ u3m_pave(c3_o nuu_o)
   }
 }
 
+/* u3m_pave_jets(): re-initialize jet dashboard hashtables.
+*/
+void
+u3m_pave_jets(void)
+{
+  _pave_jets();
+}
+
 #if 0
 /* u3m_clear(): clear all allocated data in road.
 */
diff --git a/pkg/noun/manage.h b/pkg/noun/manage.h
index 14f9cc503d..0d780cda91 100644
--- a/pkg/noun/manage.h
+++ b/pkg/noun/manage.h
@@ -88,6 +88,11 @@
         void
         u3m_pave(c3_o nuu_o);
 
+      /* u3m_pave_jets(): re-initialize jet dashboard hashtables.
+      */
+        void
+        u3m_pave_jets();
+
       /* u3m_signal(): treat a nock-level exception as a signal interrupt.
       */
         void
diff --git a/pkg/noun/urth.c b/pkg/noun/urth.c
index 0bf5473f68..cdbf77a92f 100644
--- a/pkg/noun/urth.c
+++ b/pkg/noun/urth.c
@@ -575,14 +575,11 @@ u3u_melt(void)
   }
   u3z(codc);
 
-  // We threw these away so we need to re-pave them before re-initialization.
+  // re-init all the jets and remove free space
   //
-  u3R->jed.bas_p = u3h_new();
-  u3R->jed.han_p = u3h_new();
-  u3R->jed.war_p = u3h_new();
-
-  u3j_ream();  // re-init all the jets
-  u3m_pack();  // remove free space
+  u3m_pave_jets();
+  u3j_ream();
+  u3m_pack();
 }
 
 /* our_traversal

From 09b850a5d702e02387a1ede3d6a804f8b0b3c563 Mon Sep 17 00:00:00 2001
From: Daryl Richter <daryl@ngzax.com>
Date: Fri, 19 Aug 2022 16:43:23 -0400
Subject: [PATCH 07/14] fix a refcounting issue. reorganize a bit.

---
 pkg/noun/urth.c | 35 +++++++++++++++++------------------
 1 file changed, 17 insertions(+), 18 deletions(-)

diff --git a/pkg/noun/urth.c b/pkg/noun/urth.c
index cdbf77a92f..1b564e8c85 100644
--- a/pkg/noun/urth.c
+++ b/pkg/noun/urth.c
@@ -493,7 +493,7 @@ _put(u3_noun som, u3p(u3h_root) set_p)
   //  strip tag bits from [som] to skip refcounts
   //
   u3_post hav_p = u3a_to_off(som);
-  u3h_put(set_p, u3k(som), hav_p);
+  u3h_put(set_p, som, hav_p);
 }
 
 static u3_noun
@@ -546,12 +546,17 @@ u3u_melt(void)
   u3_noun cod = u3_nul;
   u3h_walk_with(u3R->jed.cod_p, _cj_warm_tap, &cod);
 
-  u3m_reclaim(); // Throw away what we don't need
+  u3m_reclaim(); // refresh the byte-code interpreter.
   u3j_free(); // free cold & warm jet state
 
-  // NOTE: We are now in an invalid state.
-  // TODO: Free everything else we can. Joe to provide? Look at garbage collector - u3a->roc, u3a->jed, u3m_mark (mark all roots).
-  //
+  u3z(u3A->yot);  // Clear the hoon run-time cache
+  u3z(u3R->bug.mer); // Clear the "emergency" buffer.
+  u3z(u3R->bug.tax); // Clear the stack traces.
+
+  u3A->yot = 0;
+  u3R->bug.mer = 0;
+  u3R->bug.tax = 0;
+
   u3p(u3h_root) set_p = u3h_new();
 
   cod = _traverse(cod, set_p);
@@ -564,10 +569,15 @@ u3u_melt(void)
   //
   u3j_boot(c3y);
 
+  // re-init all the jets
+  //
+  u3m_pave_jets();
+
+  // restore the jet state
+  //
   u3_noun codc;
   codc = cod;
 
-  u3R->jed.cod_p = u3h_new();
   while(u3_nul != cod) {
     u3_noun kev = u3h(cod);
     u3h_put(u3R->jed.cod_p, u3h(kev), u3k(u3t(kev)));
@@ -575,23 +585,12 @@ u3u_melt(void)
   }
   u3z(codc);
 
-  // re-init all the jets and remove free space
+  // remove free space
   //
-  u3m_pave_jets();
   u3j_ream();
   u3m_pack();
 }
 
-/* our_traversal
-(a_noun, known_nouns)
-iterate known_nouns looking at the value of each one and seeing if the value of a_noun matches.
-if we find it, return the pointer to the value and decrement the ref count of a_noun if it's pointer is not.
-
-let foo = (get known_nouns a_noun)
-if ( foo != a_noun ) { lose(a_noun); return foo; }
-
-*/
-
 /* _cu_rock_path(): format rock path.
 */
 static c3_o

From b7d208896ecfbb93faebf3fda58a22800f259531 Mon Sep 17 00:00:00 2001
From: Daryl Richter <daryl@ngzax.com>
Date: Wed, 12 Oct 2022 11:59:50 -0400
Subject: [PATCH 08/14] improve comments

---
 pkg/noun/urth.c | 34 ++++++++++++++++------------------
 1 file changed, 16 insertions(+), 18 deletions(-)

diff --git a/pkg/noun/urth.c b/pkg/noun/urth.c
index 1b564e8c85..7d87eefa98 100644
--- a/pkg/noun/urth.c
+++ b/pkg/noun/urth.c
@@ -460,7 +460,7 @@ u3u_meld(void)
 }
 #endif
 
-/* BEGIN helper functions for u3u_meld
+/* BEGIN helper functions for u3u_melt
    -------------------------------------------------------------------
 */
 /* _cj_warm_tap(): tap war_p to rel
@@ -541,39 +541,37 @@ u3u_melt(void)
   //
   c3_assert( &(u3H->rod_u) == u3R );
 
-  // Get a cons list of the cold jet registrations.
+  // Store a cons list of the cold jet registrations in `cod`
   //
   u3_noun cod = u3_nul;
   u3h_walk_with(u3R->jed.cod_p, _cj_warm_tap, &cod);
 
-  u3m_reclaim(); // refresh the byte-code interpreter.
-  u3j_free(); // free cold & warm jet state
-
-  u3z(u3A->yot);  // Clear the hoon run-time cache
-  u3z(u3R->bug.mer); // Clear the "emergency" buffer.
-  u3z(u3R->bug.tax); // Clear the stack traces.
+  u3m_reclaim();     // refresh the byte-code interpreter.
+  u3j_free();        // free cold & warm jet state
 
+  u3z(u3A->yot);     // Clear the hoon run-time cache
   u3A->yot = 0;
+
+  u3z(u3R->bug.mer); // Clear the "emergency" buffer.
   u3R->bug.mer = 0;
+
+  u3z(u3R->bug.tax); // Clear the stack traces.
   u3R->bug.tax = 0;
 
-  u3p(u3h_root) set_p = u3h_new();
+  u3p(u3h_root) set_p = u3h_new(); // temp hashtable
 
-  cod = _traverse(cod, set_p);
-  u3A->roc = _traverse(u3A->roc, set_p);
+  cod = _traverse(cod, set_p);            // melt the jets
+  u3A->roc = _traverse(u3A->roc, set_p);  // melt the kernel
 
-  u3h_free(set_p);
+  u3h_free(set_p);  // release the temp hashtable
 
-  // Put the jet registrations back. Loop over cod putting them back into the cold jet
-  // dashboard. Then re-run the garbage collector.
+  // re-initialize the jets
   //
   u3j_boot(c3y);
-
-  // re-init all the jets
-  //
   u3m_pave_jets();
 
-  // restore the jet state
+  // Put the jet registrations back. Loop over cod putting them back into the cold jet
+  // dashboard. Then re-run the garbage collector.
   //
   u3_noun codc;
   codc = cod;

From 20103bf017b69386ebf946376c4381989e0bb98b Mon Sep 17 00:00:00 2001
From: Joe Bryan <joemfb@gmail.com>
Date: Thu, 11 Apr 2024 13:37:15 -0400
Subject: [PATCH 09/14] u3: revive melt, add cli args

---
 pkg/noun/urth.c |  8 +++--
 pkg/noun/urth.h |  2 +-
 pkg/vere/main.c | 88 ++++++++++++++++++++++++++++++++++++++-----------
 3 files changed, 76 insertions(+), 22 deletions(-)

diff --git a/pkg/noun/urth.c b/pkg/noun/urth.c
index 7d87eefa98..fa19368f2a 100644
--- a/pkg/noun/urth.c
+++ b/pkg/noun/urth.c
@@ -534,12 +534,14 @@ _traverse(u3_noun som, u3p(u3h_root) set_p)
 
 /* u3u_melt(): globally deduplicate memory and pack in-place.
 */
-void
+c3_w
 u3u_melt(void)
 {
+  c3_w pre_w = u3a_open(u3R);
+
   // Verify that we're on the main road.
   //
-  c3_assert( &(u3H->rod_u) == u3R );
+  u3_assert( &(u3H->rod_u) == u3R );
 
   // Store a cons list of the cold jet registrations in `cod`
   //
@@ -587,6 +589,8 @@ u3u_melt(void)
   //
   u3j_ream();
   u3m_pack();
+
+  return (u3a_open(u3R) - pre_w);
 }
 
 /* _cu_rock_path(): format rock path.
diff --git a/pkg/noun/urth.h b/pkg/noun/urth.h
index 28a3019c61..e2d6cdf22d 100644
--- a/pkg/noun/urth.h
+++ b/pkg/noun/urth.h
@@ -14,7 +14,7 @@
 
       /* u3u_melt(): globally deduplicate memory and pack in-place.
       */
-        void
+        c3_w
         u3u_melt(void);
 
       /* u3u_cram(): globably deduplicate memory, and write a rock to disk.
diff --git a/pkg/vere/main.c b/pkg/vere/main.c
index 5e2b35bff8..092042b282 100644
--- a/pkg/vere/main.c
+++ b/pkg/vere/main.c
@@ -1982,35 +1982,85 @@ _cw_meld(c3_i argc, c3_c* argv[])
 static void
 _cw_melt(c3_i argc, c3_c* argv[])
 {
-  switch ( argc ) {
-    case 2: {
-      if ( !(u3_Host.dir_c = _main_pier_run(argv[0])) ) {
-        fprintf(stderr, "unable to find pier\r\n");
-        exit (1);
+  c3_i ch_i, lid_i;
+  c3_w arg_w;
+
+  static struct option lop_u[] = {
+    { "loom",      required_argument, NULL, c3__loom },
+    { "no-demand", no_argument,       NULL, 6 },
+    { "swap",      no_argument,       NULL, 7 },
+    { "swap-to",   required_argument, NULL, 8 },
+    { "gc-early",  no_argument,       NULL, 9 },
+    { NULL, 0, NULL, 0 }
+  };
+
+  u3_Host.dir_c = _main_pier_run(argv[0]);
+
+  while ( -1 != (ch_i=getopt_long(argc, argv, "", lop_u, &lid_i)) ) {
+    switch ( ch_i ) {
+      case c3__loom: {
+        if (_main_readw_loom("loom", &u3_Host.ops_u.lom_y)) {
+          exit(1);
+        }
+      } break;
+
+      case 6: {  //  no-demand
+        u3_Host.ops_u.map = c3n;
+        u3C.wag_w |= u3o_no_demand;
+      } break;
+
+      case 7: {  //  swap
+        u3_Host.ops_u.eph = c3y;
+        u3C.wag_w |= u3o_swap;
+      } break;
+
+      case 8: {  //  swap-to
+        u3_Host.ops_u.eph = c3y;
+        u3C.wag_w |= u3o_swap;
+        u3C.eph_c = strdup(optarg);
+        break;
       }
-    } break;
 
-    case 3: {
-      u3_Host.dir_c = argv[2];
-    } break;
+      case 9: {  //  gc-early
+        u3C.wag_w |= u3o_check_corrupt;
+        break;
+      }
 
-    default: {
-      fprintf(stderr, "invalid command\r\n");
+      case '?': {
+        fprintf(stderr, "invalid argument\r\n");
+        exit(1);
+      } break;
+    }
+  }
+
+  //  argv[optind] is always "melt"
+  //
+
+  if ( !u3_Host.dir_c ) {
+    if ( optind + 1 < argc ) {
+      u3_Host.dir_c = argv[optind + 1];
+    }
+    else {
+      fprintf(stderr, "invalid command, pier required\r\n");
       exit(1);
-    } break;
+    }
+
+    optind++;
   }
 
-  u3_disk* log_u = _cw_disk_init(u3_Host.dir_c); // XX s/b try_aquire lock
-  c3_w     pre_w;
+  if ( optind + 1 != argc ) {
+    fprintf(stderr, "invalid command\r\n");
+    exit(1);
+  }
 
   u3C.wag_w |= u3o_hashless;
-  u3m_boot(u3_Host.dir_c);
 
-  pre_w = u3a_open(u3R);
-  u3u_melt();
-  u3a_print_memory(stderr, "urbit: melt: gained", (u3a_open(u3R) - pre_w));
+  u3_Host.eve_d = u3m_boot(u3_Host.dir_c, (size_t)1 << u3_Host.ops_u.lom_y);
+  u3_disk* log_u = _cw_disk_init(u3_Host.dir_c); // XX s/b try_aquire lock
 
-  u3e_save();
+  u3a_print_memory(stderr, "urbit: melt: gained", u3u_melt());
+
+  u3m_save();
   u3_disk_exit(log_u);
   u3m_stop();
 }

From 9d2efcbb6fc751f4557d16ba0eaa4c94c3b89525 Mon Sep 17 00:00:00 2001
From: Joe Bryan <joemfb@gmail.com>
Date: Thu, 11 Apr 2024 13:31:03 -0400
Subject: [PATCH 10/14] u3: updates melt to properly handle compressed noun
 references

---
 pkg/noun/urth.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pkg/noun/urth.c b/pkg/noun/urth.c
index fa19368f2a..06284b3e65 100644
--- a/pkg/noun/urth.c
+++ b/pkg/noun/urth.c
@@ -484,7 +484,7 @@ _get(u3_noun som, u3p(u3h_root) set_p)
 
   //  restore tag bits from [som]
   //
-  return hav_p | ((som >> 30) << 30);
+  return (hav_p >> u3a_vits) | ((som >> 30) << 30);
 }
 
 static inline void

From 0ae7e1d4b2bc2f01f0a353c219c1d0d79a093696 Mon Sep 17 00:00:00 2001
From: Joe Bryan <joemfb@gmail.com>
Date: Thu, 11 Apr 2024 13:37:35 -0400
Subject: [PATCH 11/14] u3: clear persistent memo cache in melt

---
 pkg/noun/urth.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/pkg/noun/urth.c b/pkg/noun/urth.c
index 06284b3e65..fa016950df 100644
--- a/pkg/noun/urth.c
+++ b/pkg/noun/urth.c
@@ -12,6 +12,7 @@
 #include "imprison.h"
 #include "jets.h"
 #include "manage.h"
+#include "options.h"
 #include "retrieve.h"
 #include "serial.h"
 #include "ur.h"
@@ -551,6 +552,9 @@ u3u_melt(void)
   u3m_reclaim();     // refresh the byte-code interpreter.
   u3j_free();        // free cold & warm jet state
 
+  u3h_free(u3R->cax.per_p);
+  u3R->cax.per_p = u3h_new_cache(u3C.per_w);
+
   u3z(u3A->yot);     // Clear the hoon run-time cache
   u3A->yot = 0;
 

From 8a4d08378d3bf129d5d6d431b864cfcf52b23be2 Mon Sep 17 00:00:00 2001
From: Joe Bryan <joemfb@gmail.com>
Date: Thu, 11 Apr 2024 15:26:30 -0400
Subject: [PATCH 12/14] u3: more efficient tag-bits restoration in melt

---
 pkg/noun/urth.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pkg/noun/urth.c b/pkg/noun/urth.c
index fa016950df..676f63539a 100644
--- a/pkg/noun/urth.c
+++ b/pkg/noun/urth.c
@@ -485,7 +485,7 @@ _get(u3_noun som, u3p(u3h_root) set_p)
 
   //  restore tag bits from [som]
   //
-  return (hav_p >> u3a_vits) | ((som >> 30) << 30);
+  return (hav_p >> u3a_vits) | (som & 0xc0000000);
 }
 
 static inline void

From ddca8bcc4fc2df64be23be25214e9fe483a22dd7 Mon Sep 17 00:00:00 2001
From: Joe Bryan <joemfb@gmail.com>
Date: Thu, 11 Apr 2024 15:26:52 -0400
Subject: [PATCH 13/14] u3: avoid unnecessary refcount churn in melt

---
 pkg/noun/urth.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/pkg/noun/urth.c b/pkg/noun/urth.c
index 676f63539a..8ef99d457a 100644
--- a/pkg/noun/urth.c
+++ b/pkg/noun/urth.c
@@ -513,6 +513,10 @@ _traverse(u3_noun som, u3p(u3h_root) set_p)
   //
   if (u3_none != (hav = _get(som, set_p)))
   {
+    if ( som == hav ) {
+      return som;
+    }
+
     u3z(som);
     return u3k(hav);
   }

From f20cfa3e884c318259e241189fb5ab218c924250 Mon Sep 17 00:00:00 2001
From: Joe Bryan <joemfb@gmail.com>
Date: Thu, 11 Apr 2024 18:11:48 -0400
Subject: [PATCH 14/14] u3: avoids unnecessary stores to memory in melt

---
 pkg/noun/urth.c | 44 +++++++++++++++++++-------------------------
 1 file changed, 19 insertions(+), 25 deletions(-)

diff --git a/pkg/noun/urth.c b/pkg/noun/urth.c
index 8ef99d457a..98f7c49f21 100644
--- a/pkg/noun/urth.c
+++ b/pkg/noun/urth.c
@@ -474,12 +474,11 @@ _cj_warm_tap(u3_noun kev, void* wit)
 }
 
 static inline u3_weak
-_get(u3_noun som, u3p(u3h_root) set_p)
+_cu_melt_get(u3p(u3h_root) set_p, u3_noun som)
 {
   u3_post hav_p = u3h_git(set_p, som);
 
-  if (u3_none == hav_p)
-  {
+  if ( u3_none == hav_p ) {
     return u3_none;
   }
 
@@ -489,7 +488,7 @@ _get(u3_noun som, u3p(u3h_root) set_p)
 }
 
 static inline void
-_put(u3_noun som, u3p(u3h_root) set_p)
+_cu_melt_put(u3p(u3h_root) set_p, u3_noun som)
 {
   //  strip tag bits from [som] to skip refcounts
   //
@@ -497,44 +496,39 @@ _put(u3_noun som, u3p(u3h_root) set_p)
   u3h_put(set_p, som, hav_p);
 }
 
-static u3_noun
-_traverse(u3_noun som, u3p(u3h_root) set_p)
+static void
+_cu_melt_noun(u3p(u3h_root) set_p, u3_noun* mos)
 {
+  u3_noun som = *mos;
   u3_weak hav;
 
   //  skip direct atoms
   //
-  if (c3y == u3a_is_cat(som))
-  {
-    return som;
+  if ( c3y == u3a_is_cat(som) ) {
+    return;
   }
 
   //  [som] equals [hav], and [hav] is canonical
   //
-  if (u3_none != (hav = _get(som, set_p)))
-  {
-    if ( som == hav ) {
-      return som;
+  if ( u3_none != (hav = _cu_melt_get(set_p, som)) ) {
+    if ( hav != som ) {
+      u3z(som);
+      *mos = u3k(hav);
     }
-
-    u3z(som);
-    return u3k(hav);
+    return;
   }
 
   //  traverse subtrees
   //
-  if (c3y == u3a_is_cell(som))
-  {
+  if ( c3y == u3a_is_cell(som) ) {
     u3a_cell *cel_u = u3a_to_ptr(som);
-
-    cel_u->hed = _traverse(cel_u->hed, set_p);
-    cel_u->tel = _traverse(cel_u->tel, set_p);
+    _cu_melt_noun(set_p, &cel_u->hed);
+    _cu_melt_noun(set_p, &cel_u->tel);
   }
 
   //  [som] is canonical
   //
-  _put(som, set_p);
-  return som;
+  _cu_melt_put(set_p, som);
 }
 
 /* u3u_melt(): globally deduplicate memory and pack in-place.
@@ -570,8 +564,8 @@ u3u_melt(void)
 
   u3p(u3h_root) set_p = u3h_new(); // temp hashtable
 
-  cod = _traverse(cod, set_p);            // melt the jets
-  u3A->roc = _traverse(u3A->roc, set_p);  // melt the kernel
+  _cu_melt_noun(set_p, &cod);      // melt the jets
+  _cu_melt_noun(set_p, &u3A->roc); // melt the kernel
 
   u3h_free(set_p);  // release the temp hashtable