halving-calculator.py: a few minor fixes

README.md

@@ -137,8 +137,6 @@ Linux, Armbian, Raspbian, Windows/MSYS2
 
 ### Download/Install
 
-> #### [Install a prebuilt bootable image (MMGenLive) on a USB stick][8]
-
 > #### [Install from source on Microsoft Windows][1]
 
 > #### [Install from source on Debian, Ubuntu, Raspbian or Armbian Linux][2]

examples/halving-calculator.py

@@ -13,7 +13,6 @@ from mmgen.common import *
 opts.init({ 'text': { 'desc':'', 'usage':'', 'options':'' }})
 
 HalvingInterval = 210000 # src/chainparams.cpp
-sample_size = 6 * 24     # about a day's worth of blocks
 
 def date(t):
 	return '{}-{:02}-{:02} {:02}:{:02}:{:02}'.format(*time.gmtime(t)[:6])
@@ -23,7 +22,7 @@ def dhms(t):
 
 def time_diff_warning(t_diff):
 	if abs(t_diff) > 60*60:
-		print('Warning: block tip time is {} {} current time!'.format(
+		print('Warning: block tip time is {} {} clock time!'.format(
 			dhms(abs(t_diff)),
 			('behind','ahead of')[t_diff<0]))
 
@@ -31,24 +30,26 @@ async def main():
 	from mmgen.rpc import rpc_init
 	c = await rpc_init()
 	tip = await c.call('getblockcount')
+	remaining = HalvingInterval - tip % HalvingInterval
+	sample_size = max(remaining,144)
 
 	# aiohttp backend will perform these two calls concurrently:
 	cur,old = await c.gathered_call('getblockstats',((tip,),(tip - sample_size,)))
 
-	time_diff_warning(int(time.time() - cur['time']))
+	clock_time = int(time.time())
+	time_diff_warning(clock_time - cur['time'])
 
-	remaining = HalvingInterval - tip % HalvingInterval
 	bdr = (cur['time'] - old['time']) / sample_size
 	t_rem = remaining * int(bdr)
-	sub = cur['subsidy'] * Decimal("0.00000001")
+	sub = cur['subsidy'] * Decimal('0.00000001')
 
 	print(f'Current block:      {tip}')
 	print(f'Next halving block: {tip + remaining}')
 	print(f'Blocks until halving: {remaining}')
 	print('Current block subsidy: {} BTC'.format(str(sub).rstrip('0')))
 	print(f'Current block discovery rate (over last {sample_size} blocks): {bdr/60:0.1f} minutes')
-	print(f'Current clock time (UTC): {date(time.time())}')
+	print(f'Current clock time (UTC): {date(clock_time)}')
 	print(f'Est. halving date (UTC):  {date(cur["time"] + t_rem)}')
-	print(f'Est. time until halving:  {dhms(cur["time"] + t_rem - int(time.time()))}')
+	print(f'Est. time until halving:  {dhms(cur["time"] + t_rem - clock_time)}')
 
 run_session(main(),do_rpc_init=False)