com_diff(), use hash tables for the vector search

patch originally provided by Bill Swartz, 2010
reduces vector search time from O(n*n) to O(n)

src/frontend/diff.c

@@ -2,6 +2,7 @@
 Copyright 1990 Regents of the University of California.  All rights reserved.
 Author: 1985 Wayne A. Christopher, U. C. Berkeley CAD Group
 Modified: 2001 Paolo Nenzi (printnum)
+Patched: 2010/2012 by Bill Swartz (hash table for vectors)
 **********/
 
 /*
@@ -14,9 +15,45 @@ Modified: 2001 Paolo Nenzi (printnum)
 #include "ngspice/sim.h"
 
 #include "diff.h"
+#include <ngspice/hash.h>
+#include <ngspice/dstring.h>
 #include "variable.h"
 
 
+static char *
+cannonical_name(char *name, SPICE_DSTRINGPTR dbuf_p)
+{
+    char *tmp;                         /* position in string */
+    char *ptr;                         /* current position in string */
+
+    spice_dstring_reinit(dbuf_p);
+
+    if (ciprefix("i(",name)) {
+        tmp = name;
+        while (*tmp != '(')
+            tmp++;
+        tmp++;
+        for (ptr = tmp; *ptr; ptr++)
+            if (isupper(*ptr))
+                tmp = spice_dstring_append_char(dbuf_p, (char)tolower(*ptr));
+            else
+                tmp = spice_dstring_append_char(dbuf_p, *ptr);
+        while (*tmp != ')')
+            tmp++;
+        *tmp = '\0';
+        tmp = spice_dstring_append(dbuf_p, "#branch", -1);
+    } else if (isdigit(*name)) {
+        spice_dstring_append(dbuf_p, "v(", -1);
+        spice_dstring_append(dbuf_p, name, -1);
+        tmp = spice_dstring_append_char(dbuf_p, ')');
+    } else {
+        tmp = spice_dstring_append(dbuf_p, name, -1);
+    }
+
+    return(tmp);
+}
+
+
 /* Determine if two vectors have the 'same' name. */
 
 static bool
@@ -79,6 +116,10 @@ com_diff(wordlist *wl)
     double d1, d2;
     ngcomplex_t c1, c2, c3;
     int i, j;
+    char *v1_name;          /* cannonical v1 name */
+    char *v2_name;          /* cannonical v2 name */
+    NGHASHPTR crossref_p;   /* cross reference hash table */
+    SPICE_DSTRING ibuf;     /* used to build cannonical name */
     wordlist *tw;
     char numbuf[BSIZE_SP], numbuf2[BSIZE_SP], numbuf3[BSIZE_SP], numbuf4[BSIZE_SP]; /* For printnum */
 
@@ -143,15 +184,28 @@ com_diff(wordlist *wl)
                 "Warning: plots %s and %s seem to be from different circuits\n",
                 p1->pl_typename, p2->pl_typename);
 
-    /* This may not be the best way to do this */
+    /* This may not be the best way to do this.  It wasn't :).  The original
+     * was O(n2) - not good.  Now use a hash table to reduce it to O(n). */
     for (v1 = p1->pl_dvecs; v1; v1 = v1->v_next)
         v1->v_link2 = NULL;
-    for (v2 = p2->pl_dvecs; v2; v2 = v2->v_next)
+
+    spice_dstring_init(&ibuf);
+    crossref_p = nghash_init(NGHASH_MIN_SIZE);
+    nghash_unique(crossref_p, FALSE);
+
+    for (v2 = p2->pl_dvecs; v2; v2 = v2->v_next) {
         v2->v_link2 = NULL;
+        v2_name = cannonical_name(v2->v_name, &ibuf);
+        nghash_insert(crossref_p, v2_name, v2);
+    }
 
-    for (v1 = p1->pl_dvecs; v1; v1 = v1->v_next)
-        for (v2 = p2->pl_dvecs; v2; v2 = v2->v_next)
-            if (!v2->v_link2 && nameeq(v1->v_name, v2->v_name) &&
+    for (v1 = p1->pl_dvecs; v1; v1 = v1->v_next) {
+        v1_name = cannonical_name(v1->v_name, &ibuf);
+        for (v2 = nghash_find(crossref_p, v1_name);
+             v2;
+             v2 = nghash_find_again(crossref_p, v1_name))
+        {
+            if (!v2->v_link2 &&
                 ((v1->v_flags & (VF_REAL | VF_COMPLEX)) ==
                  (v2->v_flags & (VF_REAL | VF_COMPLEX))) &&
                 (v1->v_type == v2->v_type))
@@ -160,6 +214,11 @@ com_diff(wordlist *wl)
                 v2->v_link2 = v1;
                 break;
             }
+        }
+    }
+
+    spice_dstring_free(&ibuf);
+    nghash_free(crossref_p, NULL, NULL);
 
     for (v1 = p1->pl_dvecs; v1; v1 = v1->v_next)
         if (!v1->v_link2)