findvec(), use hash tables for the vector search

patch originally provided by Bill Swartz, 2010
reduces vector search time from O(n) to O(1)

src/frontend/plotting/plotting.c

@@ -6,7 +6,8 @@
 
 struct plot constantplot = {
     "Constant values", Spice_Build_Date, "constants",
-    "const", NULL, NULL, NULL, NULL, NULL, NULL, TRUE, 0
+    "const", NULL, NULL, NULL, NULL, NULL, NULL, NULL,
+    TRUE, FALSE, 0
 };
 
 struct plot *plot_cur = &constantplot;

src/frontend/vectors.c

@@ -19,6 +19,7 @@ Author: 1985 Wayne A. Christopher, U. C. Berkeley CAD Group
 #include "dimens.h"
 #include "../misc/misc_time.h"
 #include "vectors.h"
+#include "ngspice/dstring.h"
 #include "plotting/plotting.h"
 
 #ifdef XSPICE
@@ -28,13 +29,46 @@ struct dvec *EVTfindvec(char *node);
 #endif
 
 
+static void
+vec_rebuild_lookup_table(struct plot *pl)
+{
+    int cnt;                            /* count entries */
+    struct dvec *d;                     /* dynamic vector */
+    NGHASHPTR lookup_p;                 /* lookup table for speed */
+    SPICE_DSTRING dbuf;                 /* dynamic buffer */
+    char *lower_name;                   /* lower case name */
+
+    if (pl->pl_lookup_table) {
+        nghash_empty(pl->pl_lookup_table, NULL, NULL);
+    } else {
+        cnt = 0;
+        for (d = pl->pl_dvecs; d; d = d->v_next)
+            cnt++;
+        pl->pl_lookup_table = nghash_init(cnt);
+        /* allow multiple entries */
+        nghash_unique(pl->pl_lookup_table, FALSE);
+    }
+    lookup_p = pl->pl_lookup_table;
+    spice_dstring_init(&dbuf);
+    for (d = pl->pl_dvecs; d; d = d->v_next) {
+        spice_dstring_reinit(&dbuf);
+        lower_name = spice_dstring_append_lower(&dbuf, d->v_name, -1);
+        nghash_insert(lookup_p, lower_name, d);
+    }
+    spice_dstring_free(&dbuf);
+    pl->pl_lookup_valid = TRUE;
+}
+
+
 /* Find a named vector in a plot. We are careful to copy the vector if
  * v_link2 is set, because otherwise we will get screwed up.  */
 static struct dvec *
 findvec(char *word, struct plot *pl)
 {
+    SPICE_DSTRING dbuf;                 /* dynamic buffer */
+    char *lower_name;                   /* lower case name */
+    char *node_name;
     struct dvec *d, *newv = NULL, *end = NULL, *v;
-    char buf[BSIZE_SP];
 
     if (pl == NULL)
         return (NULL);
@@ -115,15 +149,37 @@ findvec(char *word, struct plot *pl)
         return (newv);
     }
 
-    for (d = pl->pl_dvecs; d; d = d->v_next)
-        if (cieq(word, d->v_name) && (d->v_flags & VF_PERMANENT))
+    if (!pl->pl_lookup_valid)
+        vec_rebuild_lookup_table(pl);
+
+    spice_dstring_init(&dbuf);
+    lower_name = spice_dstring_append_lower(&dbuf, word, -1);
+
+    for (d = nghash_find(pl->pl_lookup_table, lower_name);
+         d;
+         d = nghash_find_again(pl->pl_lookup_table, lower_name))
+    {
+        if (d->v_flags & VF_PERMANENT)
             break;
+    }
+
     if (!d) {
-        (void) sprintf(buf, "v(%s)", word);
-        for (d = pl->pl_dvecs; d; d = d->v_next)
-            if (cieq(buf, d->v_name) && (d->v_flags & VF_PERMANENT))
+        spice_dstring_reinit(&dbuf);
+        spice_dstring_append(&dbuf, "v(", -1);
+        spice_dstring_append_lower(&dbuf, word, -1);
+        node_name = spice_dstring_append_char(&dbuf, ')');
+
+        for (d = nghash_find(pl->pl_lookup_table, node_name);
+             d;
+             d = nghash_find_again(pl->pl_lookup_table, node_name))
+        {
+            if (d->v_flags & VF_PERMANENT)
                 break;
+        }
     }
+
+    spice_dstring_free(&dbuf);
+
 #ifdef XSPICE
     /* gtri - begin - Add processing for getting event-driven vector */
 
@@ -728,6 +784,7 @@ vec_new(struct dvec *d)
     if (plot_cur == NULL) {
         fprintf(cp_err, "vec_new: Internal Error: no cur plot\n");
     }
+    plot_cur->pl_lookup_valid = FALSE;
     if ((d->v_flags & VF_PERMANENT) && (plot_cur->pl_scale == NULL))
         plot_cur->pl_scale = d;
     if (!d->v_plot)
@@ -791,6 +848,7 @@ vec_free_x(struct dvec *v)
 
     /* Now we have to take this dvec out of the plot list. */
     if (pl != NULL) {
+        pl->pl_lookup_valid = FALSE;
         if (pl->pl_dvecs == v) {
             pl->pl_dvecs = v->v_next;
         } else {

src/include/ngspice/plot.h

@@ -4,6 +4,7 @@
 #include "ngspice/wordlist.h"
 #include "ngspice/bool.h"
 #include "ngspice/dvec.h"
+#include "ngspice/hash.h"
 
 struct ccom;
 
@@ -17,10 +18,12 @@ struct plot {
     struct dvec *pl_dvecs;	/* The data vectors in this plot. */
     struct dvec *pl_scale;	/* The "scale" for the rest of the vectors. */
     struct plot *pl_next;	/* List of plots. */
+    NGHASHPTR pl_lookup_table;	/* for quick lookup of vectors */
     wordlist *pl_commands;	/* Commands to execute for this plot. */
     struct variable *pl_env;	/* The 'environment' for this plot. */
     struct ccom *pl_ccom;	/* The ccom struct for this plot. */
     bool pl_written;		/* Some or all of the vecs have been saved. */
+    bool pl_lookup_valid;	/* vector lookup table valid */
     int pl_ndims;		/* Number of dimensions */
 } ;