+timeEpochNS() {
+ # Desc: Get epoch nanoseconds
+ # Usage: timeEpochNS
+ # Version 0.2.3
+ # Input: arg1: 'date'-parsable timestamp string (optional)
+ # Output: Nanoseconds since 1970-01-01
+ # Depends: date 8, cut 8, yell()
+ # Ref/Attrib: Force base 10 Bash arith with '10#'. https://stackoverflow.com/a/24777667
+ local argTime timeCurrent timeInput timeEpochFloat timeEpochInt
+ local timeEpochNsFrac timeEpochNs
+
+ argTime="$1";
+
+ # Get Current Time
+ timeCurrent="$(date --iso-8601=ns)"; # Produce `date`-parsable current timestamp with resolution of 1 nanosecond.
+
+ # Decide to parse current or supplied time
+ ## Check if time argument empty
+ if [[ -z "$argTime" ]]; then
+ ## T: Time argument empty, use current time
+ timeInput="$timeCurrent";
+ else
+ ## F: Time argument exists, validate time
+ if date --date="$argTime" 1>/dev/null 2>&1; then
+ ### T: Time argument is valid; use it
+ timeInput="$argTime";
+ else
+ ### F: Time argument not valid; exit
+ yell "ERROR:Invalid time argument supplied. Exiting."; exit 1;
+ fi;
+ fi;
+ # Construct and deliver nanoseconds since 1970-01-01
+ timeEpochFloat="$(date --date="$timeInput" +%s.%N)"; # Save ssss.NNNNNNNNN
+ timeEpochInt="$(echo "$timeEpochFloat" | cut -d. -f1)"; # Get ssss
+ timeEpochNsFrac="$(echo "$timeEpochFloat" | cut -d. -f2)"; # Get NNNNNNNNN
+ timeEpochNs="$(( (10#"$timeEpochInt" * 10**9) + (10#"$timeEpochNsFrac") ))";
+ echo "$timeEpochNs";
+} # Nanoseconds since 1970-01-01
+magicBufferSleepPID() {
+ # Desc: Compensates for lag so buffer rounds start every bufferTTL seconds
+ # Input: vars: bufferTTL, errReset
+ # # Input: array: errorHistory errResetx10e3
+ # Output: vars: bufferTTL_AdjFloat
+ # Re/Attrib: https://en.wikipedia.org/wiki/PID_controller#Standard_versus_parallel_(ideal)_form
+ local buffer_ttl_ns k_p t_i t_d
+ local timeBufferStartNS timeBufferStartNSExp errNS errReset errRate
+ local adj buffer_ttl_adj_ns buffer_ttl_adj_int buffer_ttl_adj_floatfrac
+ # local errNSx10e3 errResetx10e3 errRatex10e3
+ # local errorHistorySize
+
+ # ## Define errorHistorySize
+ # errorHistorySize=100;
+ ## Define bufferTTL in nanoseconds
+ buffer_ttl_ns=$((bufferTTL * 10**9)) && vbm "buffer_ttl_ns:$buffer_ttl_ns";
+
+ ### PID Control factors
+ k_p=1; # Gain for compensating buffer round lag
+ t_i="$(((4)*buffer_ttl_ns/(1)))"; # Consider this number of past nanoseconds to eliminate error
+ t_d="$(((1)*buffer_ttl_ns/(1)))"; # Predict value this number of nanoseconds into the future
+
+ # Calculate Error, errNS, in nanoseconds
+ ## Get current time
+ timeBufferStartNS="$(timeEpochNS)" && vbm "timeBufferStartNS :$timeBufferStartNS";
+ ## Calculate expected time (from start time, current buffer round number, nominal bufferTTL)
+ timeBufferStartNSExp="$(( (timeBufferFirstNS) + (buffer_ttl_ns * bufferRound) ))" && vbm "timeBufferStartNSExp:$timeBufferStartNSExp";
+ ## Calculate error (diff between timeBufferStartNSExp and timeBufferStartNS; usually negative)
+ errNS="$(( timeBufferStartNSExp - timeBufferStartNS ))" && vbm "errNS:$errNS";
+# errNSx10e3="$((errNS*10**3))" && vbm "errNSx10e3:$errNSx10e3";
+ # ## Append error to errorHistory
+ # errorHistory+=("errNS");
+ # ### Trim errorHistory array if over errorHistorySize
+ # while [[ "${#errorHistory[@]}" -gt "errorHistorySize" ]]; then do
+ # unset "errorHistory[0]"; # remove oldest entry, creating sparse array
+ # errorHistory=("${errorHistory[@]}"); # reindex sparse array
+ # vbm "STATUS:Trimmed errorHistory array. Entry count:${#errorHistory[@]}";
+ # done;
+
+ # Calculate errReset in nanoseconds^2
+ ## errReset = int(errHistory(t),wrt(delta_buffer_ttl))
+ ## Integrate errorHistory with respect to time
+ # for value in "${errorHistory[@]}"; do
+ # errReset=$(( errReset + ( value*buffer_ttl_ns ) ));
+ # done;
+ vbm "errReset(orig):$errReset"
+ errReset="$(( (errReset + (errNS*buffer_ttl_ns)) ))" && vbm "errReset(post):$errReset";
+# errResetx10e3="$(( ( errResetx10e3 + ( errNSx10e3 * buffer_ttl_ns ) )*10**3 ))" && vbm "errResetx10e3:$errResetx10e3";
+
+ # Calculate errRate in nanoseconds per nanosecond
+ errRate="$(( errNS / buffer_ttl_ns ))" && vbm "errRate:$errRate";
+# errRatex10e3="$(( ( errNSx10e3 ) / buffer_ttl_ns ))" && vbm "errRatex10e3:$errRatex10e3";
+
+ # Debug
+ vbm "errNS :$errNS";
+ vbm "errResetTerm:$((errReset/t_i))";
+ vbm "errRateTerm :$((errRate*t_d))";
+
+ # Calculate PID control signal
+ ## adj = k_p * (errNS + errReset/t_i + errRate*t_d)
+ adj="$(( k_p*(errNS + errReset/t_i + errRate*t_d) ))" && vbm "adj:$adj";
+# adj="$((k_p*(errNSx10e3 + (errResetx10e3/t_i) + (errRatex10e3*t_d) )/(10**3)))" && vbm "adj:$adj";
+
+ # Calculate bufferTTL_AdjFloat from adj (ns)
+ ## Calculate buffer_ttl_adj in nanoseconds (buffer_ttl_adj_ns = buffer_ttl_ns + adj)
+ buffer_ttl_adj_ns="$((buffer_ttl_ns + adj))" && vbm "buffer_ttl_adj_ns:$buffer_ttl_adj_ns";
+ ## Calculate integer seconds
+ buffer_ttl_adj_int="$((buffer_ttl_adj_ns/(10**9)))" && vbm "buffer_ttl_adj_int:$buffer_ttl_adj_int";
+ ### Catch negative integer seconds, set minimum of bufferTTL/10 seconds
+ if [[ "$buffer_ttl_adj_int" -le "$((bufferTTL/10))" ]]; then
+ buffer_ttl_adj_int="$((bufferTTL/10))";
+ yell "WARNING:Buffer lag adjustment yielded negative seconds.";
+ fi;
+ ## Calculate nanosecond remainder
+ ### Remove integer
+ buffer_ttl_adj_floatfrac="$((buffer_ttl_adj_ns - (buffer_ttl_adj_int*(10**9)) ))" && vbm "buffer_ttl_adj_floatfrac:$buffer_ttl_adj_floatfrac";
+ ### Calc absolute value of fraction (by removing '-' if present; see https://stackoverflow.com/a/47240327
+ buffer_ttl_adj_floatfrac="${buffer_ttl_adj_floatfrac#-}" && vbm "buffer_ttl_adj_floatfrac:$buffer_ttl_adj_floatfrac";
+ ## Form float bufferTTL_AdjFloat (function output)
+ bufferTTL_AdjFloat="$buffer_ttl_adj_int"."$buffer_ttl_adj_floatfrac" && vbm "bufferTTL_AdjFloat:$bufferTTL_AdjFloat";
+ vbm "STATUS:Calculated adjusted bufferTTL (seconds):$bufferTTL_AdjFloat";
+} # Calc bufferTTL_AdjFloat so buffer starts every bufferTTL seconds
projects / EVA-2020-02.git / blobdiff