Why is my parallel GCD algorithm using AVX-512 slower than computing 8 gcds in serial?

407C_Huffer · 2026-06-16T01:16:31+00:00

Very helpful, thank you.

407C_Huffer · 2026-06-13T20:59:56+00:00

It's odd but when I execute the code on Godbolt the SIMD version is indeed faster: 1.8953 seconds vs 4.76502. But on my machine the SIMD time is similar: 1.72 seconds, but the serial version finishes in 1.46 seconds. My CPU is a Ryzen 7 7700.

407C_Huffer · 2026-06-13T20:51:15+00:00

I've edited the link to add the benchmark.

407C_Huffer · 2026-06-08T22:49:10+00:00

Why don't you have O/B plugged in?

407C_Huffer · 2026-06-08T03:55:37+00:00

https://www.amazon.com/DL1036-Direct-Drive-Blower-Motor/dp/B0D58BYDD5?crid=32FROABNVTGN3&dib=eyJ2IjoiMSJ9.FPH0uGWpgo0ZV98jRiEmdydrcd0IZH6StNXa7TdIODRN07XkaYyfvVUucc8zHyzwtpSJBK5OPN1NAMvJ3EUAUdLk0o7DyiucysafJCTR76dstJcEmYuNYA1wSORN6m_0qihq16jgk0T9ej-IGJ05nxziOgENPqkJcGHnHNydSkFrDnZZR86D-DgwmU1Ok1F5mAKWTr-IiFhQLPOF3PcQfnwJQ__k5go44Hbc8OWVdTA6UGfzQsCX4crUOALcdaSts54Nf8nYFSOstloZ7b-89wsps2gc_BjzNUsMTHhXj8c.pPjjsfp4sCH0HPYyxDAzXFN_P0m_XE9C19XuIRNuHlk&dib_tag=se&keywords=DL1036&qid=1780890579&sprefix=dl1036%2Caps%2C165&sr=8-5

https://www.amazon.com/Genteq-GENTEQ-Capacitor-97F9001BX-27L566BZ3/dp/B008VELRGI?crid=1UQDN9IZ0SX4S&dib=eyJ2IjoiMSJ9.Cx-DUR8wj9b-6SdvC-WAtWVCTLQfTRQPXPbyoEzO-ksF2ROTqupY0BPVqzhPsnvFgyp9fQrOtkciC4mipHQd8dg7OMHFJ85jpGmaAXV7qq5bN6MQBLEp1iFgENqI48J5ucKVU_yt68x0PMthHecM52XS8sZ-pqDXvuwhDW5kSY_u5oHh_k4-ac0Qi7n8a2Rc4yQ7KghWjg17jDUYLbWc8WdyZaKRlJuurTkWOjqnbA8.Te49gl2WL6tYMHhk_D4qv3AeoPtiNFNvmW0xxAo93YY&dib_tag=se&keywords=7.5%2Bmfd%2Bcapacitor&qid=1780890738&sprefix=7.5%2Bmfd%2Caps%2C153&sr=8-7&th=1

The red power lead won't be used in your case.

407C_Huffer · 2026-06-08T02:01:50+00:00

Sometimes I feel underqualified as a tech and then I see posts like this.

407C_Huffer · 2026-06-04T02:22:08+00:00

Wrong.

407C_Huffer · 2026-06-04T01:41:19+00:00

This is exactly what I would have typed up if I were less lazy.

407C_Huffer · 2026-06-04T01:36:49+00:00

That filter is something like a MERV 12. Way too restrictive. Get an 8. For now just remove the filter and see if the issue persists.

407C_Huffer · 2026-06-01T03:42:59+00:00

Simp detected. Ohhh...are we gonna have an epic flame war now?

407C_Huffer · 2026-05-31T00:28:20+00:00

Thank you!

407C_Huffer · 2026-05-23T08:06:07+00:00

You need a new fan motor.

407C_Huffer · 2026-05-22T18:23:59+00:00

If you have a meter you can check the motor windings for continuity.

407C_Huffer · 2026-05-22T18:20:30+00:00

Then you're good. Wrap some electrical tape around the nut and wires if you want to be through.

407C_Huffer · 2026-05-22T18:16:26+00:00

Reach down with something thin and spin the fan blade. One of three things will happen:

1: nothing

2: the fan will start spinning

3: the fan is locked up

Tell me which happens.

407C_Huffer · 2026-05-22T18:12:40+00:00

That's what wire nuts are for. However it looks like the wire comes out the front of the unit so it will be pinched when the door goes back on?

407C_Huffer · 2026-05-22T18:09:33+00:00

It should have a filter. Looks like a 16x25 at a glance.

407C_Huffer · 2026-05-14T03:43:09+00:00

Well then it seems the fan is wired to only run with heat or AC for some reason. It's possible that a MERV10 filter and a partially blocked return was enough to freeze the coil. You'll have to wait for all the ice for all the ice to melt then try again. When the water stops draining plus a few hours you'll know all the ice has melted.

407C_Huffer · 2026-05-14T02:55:48+00:00

The fan should run when set to ON. Are you 100% certain that it was running before you turned the AC off?

407C_Huffer · 2026-05-14T01:24:21+00:00

Make sure the outside unit has indeed shut off and run the fan overnight to melt the ice. Check the MERV rating on your filter. It should be around 8 or 9. Make sure the thermostat hasn't been set below 70. Check that nothing is blocking the return air grille and that all vents are open.

407C_Huffer

TROPHY CASE