Dependent vs Independent Parallel: When to Use Each

Independent parallel machines split one operation's work so the job finishes faster, while dependent parallel machines run in exact lockstep with a primary machine, copying its timing and scaling its hours by a factor. The two look similar on a Gantt, several bars on several machines at the same time, but they answer opposite questions. Independent asks "how do I divide this load to finish sooner?" Dependent asks "how do I run this one operation on several machines that must move together?" EDGEBIC by User Solutions supports both, and picking the wrong one either wastes speed you could have had or breaks an operation that must stay synchronized.

Independent parallel: divide the work

Independent parallel treats several machines as interchangeable runners for one operation. The engine splits the hours across them, checks and consumes each machine's capacity separately, and the job finishes when the slowest split finishes. This is the tool when the machines are genuinely alternatives and your goal is speed.

A paint shop with a rush order shows the shape. One thousand units, two booths at 100 units per day, five days to deliver:

Without parallel: 1000 / 100 per day = 10 days -> miss the date
With two independent booths: 500 each over 5 days = 1000 in 5 days -> meet it

Each booth is scheduled independently with its own capacity consumed, and both run at once. The constraint is that all the machines in the group must find a common free slot at the same start. That is the all-or-nothing rule: the engine searches forward for a date and shift where every machine has capacity together, and if one is fully booked the whole group waits for the next common opening.

Dependent parallel: run in lockstep

Dependent parallel is mirroring. One primary machine drives the operation, and one or more secondary machines copy its schedule exactly: the same start, the same end, the same instance assignment. The mirrors' hours are scaled by a factor, and capacity is bypassed for the copies, because they are not separate jobs competing for the resource. They are one physical operation spread across hardware that must move together.

Multi-spindle drilling is the classic case. Three hundred holes, 30 hours on a single drill, three drill heads that must work the part at once:

Single drill: 30 hours
Three dependent heads at a splitting factor: 10 hours

08:00 to 18:00
Drill-1 (primary):  holes 1 to 100    (10 h)
Drill-2 (mirror):   holes 101 to 200  (10 h, same start and end)
Drill-3 (mirror):   holes 201 to 300  (10 h, same start and end)

All three start and finish together. Because the mirrors bypass capacity, a shift can show more than 100 percent allocation, which is correct: the same physical work is counted on three machines locked together. The engine only ever schedules the group when all the machines share a common shift and can start simultaneously.

The trade-off, in a table

The deciding question is physical. If the machines could each finish their share and hand off separately, they are independent. If the operation only makes sense with them moving as one, they are dependent.

What the factor does in each mode

The factor behaves differently between the two. In independent parallel, it governs how the work splits across machines. In dependent parallel, it scales the hours the mirror is charged relative to the primary, without touching the timestamps. A factor of 1.0 mirrors the parent exactly; 0.5 charges half the hours, modeling a faster mirror; 2.0 charges double for a slower one. The start and end never move for a dependent mirror, only the hours it books.

Setup is never scaled by the factor in either mode. A machine can run fast and set up slow, so setup is handled independently.

Choosing between them

Reach for independent parallel when you want an urgent order done sooner and the machines are interchangeable for the split. Reach for dependent parallel when the operation physically requires several machines in lockstep. Getting it wrong is visible: an independent configuration on a multi-spindle job would let the heads drift to different times and the part would be wrong; a dependent configuration on two paint booths would mirror one job onto both instead of splitting two jobs across them.

Both are distinct from splitting work across identical machines inside one work center, which is instance load balancing vs dedicated instance scheduling, and from offering the engine a choice of interchangeable machines, which is a machine pool vs an alternate work center. For the full mechanism, including the four validation gates that guarantee a simultaneous start, see parallel and alternate work centers explained, and the scheduling engine guide places parallel scheduling inside the whole pipeline. Model your own synchronized operations in EDGEBIC.